Uh oh ....

[DeLorean03]

So I went for a drive today. The car was running absolutely beautifully. Then when I left a restaurant to head home, I noticed the car was stumbling bad, like the engine had a miss in it pretty badly. It was in all gears (auto trans) and drives. Drove with speeds up to 55mph, and the engine was missing the whole way home. Got it home, did the fuel pressure checks - all came out well. Looked at the plugs; they all were uniform with white/tan porcelain and clean electrodes.

Then I got to the compression test:

Cylinder 1: 105/115/120 (did it 3x)
Cylinder 2: 130
Cylinder 3: 130
Cylinder 4: 140
Cylinder 5: 130
Cylinder 6: 140

Obviously, the one I'm eyeballing is #1 ... and with x > 10% difference, I am not pleased.

So tell me, how bad is it? What do you all think? What are your thoughts after seeing those numbers (outside of the first word that came to my mind: DOOM).

NOTE: It just occurred to me, I did NOT have the throttle fully opened while doing this. I may need to re-do the tests tomorrow to make 100% sure.

[NightFlyer]

What you describe in terms of engine behavior sounds like an ignition problem. I'd start by checking or changing the plugs, wires, cap, and rotor.

Best of luck!

[Ron]

+1

Seems iffy for you to have a "noticeable" miss with those numbers. Definitely redo the check with the throttle AND plate open (W/O fuel pressure of course).
You might try pulling the plug wires one at a time while it is running to get another clue or two...

[DeLorean03]

Man, I am sucking at this engine compression test stuff....

It just also hit me, the engine was...."warm" in terms of being turned off for about two hours, but the aluminum of the engine was VERY tolerable - in other words - the engine was not "uncomfortably warm" .... and my understanding is the engine does need to be warm when performing a compression test for "less leakage" in the results.

So, are two people absolutely required for this? I did this by myself, and I'm kind of scratching my head as to why two people are needed.


Also, other questions:

1. Should ALL the spark plugs be pulled while doing each compression test, or is it ok to have all the spark plugs and plug wire boot ends installed while testing any one cylinder?

2. If I'm by myself, could I just hold down the accelerator while cranking the engine? Wouldn't holding the accelerator pedal down fully accomplish both the throttle plates being wide open and the air-flow sensor plate being depressed fully?

3. I have now heard of doing both a wet and dry test on each cylinder. The wet test is done by putting in "30 weight oil" into a cylinder. My question - is 30 weight oil simply available at any auto store? I did a search and got some results such as this, but I just wanted to ask and make sure from everyone here:

30 Weight oil...? (http://www.autozone.com/autozone/accessories/AutoZone-Non-detergent-engine-oil-SAE-30-1-qt/_/N-26qq?itemIdentifier=692186_0_0_)

I sure do hope it's just ignition related. Having a miss while driving at 55 mph made me a bit uneasy to say the least.

[Silverbullet]

The 30 weight oil is to try to guess if it is rings of a valve... the oil will seal bad rings for the test....

[Ron]

It doesn't matter if you check the compression on one cylinder at a time or not.
To find a miss due to compression, it don't really matter hot or cold.
The second person is so that one can ensure that there is no restriction of air getting into the cylinder(s)....Idealy, you want to hold the plate open, ie do not make the air flow open it.
No reason to use oil for this situation, it will only aim you to why the compression is down (if it actually is). -- You can use the same oil you run in the engine W/O any problems (A lot of Ds running 10W30 out there. If a store has oil, they have a 30 weight of some kind ;-)

[Jim D]

I also agree that it sounds like an electrical ignition issue. Just a quick simple test is to wait until it's dark and start the engine, accelerate and look for arcing around the plug wires. A plug wire may have come lose or have a short, I can't see compression being an issue based on how you described it. Good luck!

[Kenny_Z]

When I did a compression test on my Monte the engine was cold, fuel and spark were shut off, and I used a remote starter trigger. You turn the engine over until your tester peaks a couple of times at the same range. It should only take a few revolutions. I'd assume on the D you could just take the W pipe off to make sure enough air was making it into the engine. I never had that issue with the Monte.

On a compression test you don't want more than a 15 percent variance between the highest and lowest reading. You can use a little oil in the lowest cylinder to see if the valves or the rings are an issue. If the reading is the same your valves are an issue and if the reading is higher your rings are the problem. Your compression is fine. The culprit is something else.

[Dangermouse]

Also check that an injector hasn't popped out. I had that happen once, due to weak spring clips I believe. Didn't pop all the way out, but enough to throw the firing off.

[David T]

Compression isn't the first thing that would come to mind for a miss. You cannot rule out a fuel problem either, like a misbehaving injector. As for the low compression, you may just need a valve adjustment since you say all of the plugs looked good, it is probably not rings. I agree, for it to come on suddenly it is most likely some kind of electrical/ignition problem.
David Teitelbaum

[DeLorean03]

So I tore the engine down to the rotor and cap. Tested all my plug wires - all gave me readings from 410 - 630 ohms - no outliers. Took the cap and rotor off - cleaned up all the contacts with a wire brush on a dremel so they're nice and clean now. Made absolutely sure all the plugs were seated strongly in the cap. Re-assembled and no change. Swapped fuel pumps (even though fuel pressure was good) - no change.

Fuel pressures are all good. Plug wires all have consistent ohm readings. Cap and rotor contacts have now been cleaned. Sounds like fuel and ignition system check out pretty well.

I did an old-school trick where you put a dollar bill over your exhaust while the car is running. If everything is all pretty good with your engine, the dollar bill should not try to enter the exhaust pipe. As the car was running, the exhaust did try to suck the dollar back into the pipe....

[NightFlyer]

Are you certain you're getting sufficient current to the distributor? Do you have a spare working coil that you could try?

If fuel, electrical/ignition, and rings all look good, then the only other thing I would suspect is a valve problem. If you have the intake off, might as well take the valve covers off, check for anything obvious (bent or leaky valve), and at the very least have them re-adjusted. After all, gaskets aren't too expensive and you really don't want to drive it until the problem is figured out to avoid risking further/worse damage occurring.

You aren't leaking any kind of fluids from the engine, are you? When running ruff, you're not getting any white or black/blue smoke from the exhaust, right?

[Silverbullet]

Also the ohms reading on the wires does not mean it was not arching... Lights off in a dark place works, and listen for snaping...

[Bitsyncmaster]

I've found a few bad distributor caps in my life time of working on engines. Not a common problem so it's one of the last things you try.

[David T]

I have also seen bad rotors. If you think you have ruled out an ignition problem and it isn't mechanical, you are left with fuel. Check each injector. A bad injector could definitely cause a misfire. It wouldn't hurt to look for arcing in low light. A blue glow or sparking is certainly an indication of a high voltage breakdown. You cannot see if the boot on the spark plug is arcing though.
David Teitelbaum

[DeLorean03]

Are you certain you're getting sufficient current to the distributor? Do you have a spare working coil that you could try?

If fuel, electrical/ignition, and rings all look good, then the only other thing I would suspect is a valve problem. If you have the intake off, might as well take the valve covers off, check for anything obvious (bent or leaky valve), and at the very least have them re-adjusted. After all, gaskets aren't too expensive and you really don't want to drive it until the problem is figured out to avoid risking further/worse damage occurring.

You aren't leaking any kind of fluids from the engine, are you? When running ruff, you're not getting any white or black/blue smoke from the exhaust, right?

This is the "big one" I'm wondering about. The miss is extremely cycle-lic in nature; it does not seem to be random or "travel around" the engine. I am very suspicious of cylinder 1 - not only because of the compression test, but also because as the engine warms up, I hear a tapping or a knocking sound. I have only heard this once though and that was last night. I have not let the car get that hot since so I cannot say definitively that this happens every time the car warms up yet.

I did have a puff of white smoke come out of my exhaust, but that was also after testing some of my fuel injectors so I think that was just unburned fuel in my exhaust.

I do have new valve cover gaskets ready to go if I do have to go into the valves. We'll have to see. The car is at Ken Koncelik's now to give me some sanity. I worked on this for nearly 24 straight hours. I am not working on the car again until next Thursday at the earliest.


Also the ohms reading on the wires does not mean it was not arching... Lights off in a dark place works, and listen for snaping...

So when doing this, do you just have the engine running as normal? Do you take the plug wires off or do anything else to test this? This is new territory for me, so please excuse if the questions sound silly.


I've found a few bad distributor caps in my life time of working on engines. Not a common problem so it's one of the last things you try.


I have also seen bad rotors.

I have a strong suspicion the mixture unit will be coming back off, and if so, new cap and rotor are going in.


I have also seen bad rotors. If you think you have ruled out an ignition problem and it isn't mechanical, you are left with fuel. Check each injector. A bad injector could definitely cause a misfire. It wouldn't hurt to look for arcing in low light. A blue glow or sparking is certainly an indication of a high voltage breakdown. You cannot see if the boot on the spark plug is arcing though.
David Teitelbaum

The problem there, David, is my fuel pressures all are good. System pressure was 78 psi, control pressure was 58 psi, and rest pressure was 43 psi. I did check fuel injectors 1 through 4 (I was losing daylight or I would gotten all 6), and their spray patterns were great. Can fuel components still be bad with fuel pressures checking out great?

I know I already asked this earlier - how exactly do I "check for arcing/blue light" ?

[NightFlyer]

Other than trying another coil, together with the new cap and rotor, the only other thing that's fairly easy that I can recommend is checking to make sure you don't have a vacuum leak anywhere. Other than that, and assuming everything else is good, then I'm afraid that the valve covers will probably have to come off.

Best of luck!

[DMCMW Dave]

I know I already asked this earlier - how exactly do I "check for arcing/blue light" ?

Run the engine in the dark and look at it.

[Ron]

There is something that I think may need to be cleared up here- Does it miss at all RPMs?

====

Did you do the compression checks again with the throttle and plate open?
Did you try pulling one plug wire at a time while running? (Pick the best RPM to hear it -- Try at high and low RPM regardless. Record RPM and drop for each cylinder. Also listen for the miss to "join"/drop the one you create by pulling each wire... )

[DeLorean03]

Other than trying another coil, together with the new cap and rotor, the only other thing that's fairly easy that I can recommend is checking to make sure you don't have a vacuum leak anywhere. Other than that, and assuming everything else is good, then I'm afraid that the valve covers will probably have to come off.

Best of luck!

Yeah, I am thinking that too. If it has to be that way, it has to be that way. I am also going to check the ignition timing. I can't imagine it would have gone that badly that randomly, but I'm trying to check all my other options before pulling that valve covers.


Run the engine in the dark and look at it.

I love the simple explanations (: !


There is something that I think may need to be cleared up here- Does it miss at all RPMs?

====

Did you do the compression checks again with the throttle and plate open?
Did you try pulling one plug wire at a time while running? (Pick the best RPM to hear it -- Try at high and low RPM regardless. Record RPM and drop for each cylinder. Also listen for the miss to "join"/drop the one you create by pulling each wire... )

You know, I don't see the RPMs go down when it's running, but it clearly feels like a miss. Give me a bit more time - I'll get back to you on this one.

[DeLorean03]

There is something that I think may need to be cleared up here- Does it miss at all RPMs?

====

Did you do the compression checks again with the throttle and plate open?
Did you try pulling one plug wire at a time while running? (Pick the best RPM to hear it -- Try at high and low RPM regardless. Record RPM and drop for each cylinder. Also listen for the miss to "join"/drop the one you create by pulling each wire... )

So I haven't been to my car since you asked this, but I will try to answer to the best of my ability:

1. When the car misses, I don't recall seeing the techometer needle bounce up or down at all. It seemed steady even when the engine missed.

2. I have not had an opportunity to run the compression check again.

3. I did experiment with pulling spark plug wires off of cylinder 1 and 2 just to see what would happen. Last I recall from Thursday, there didn't seem to be any massive change when spark plug wires were taken off of 1 or 2. I could "hear" a difference as the plug wires were being slipped back on their respective plugs, but it was very, very minimal. I would almost say if you weren't listening for the change, you wouldn't have even known a plug wire had been pulled.

I need to take videos of the car idling. It is unbelieveable how bad yet clear the misfire is.

[DeLorean03]

Oh, there is one other thing now that I think about it.

As I was checking the fuel tank for debris, I noticed that a white label had fallen into the tank. I recognized it from when I swapped pumps out in January. It was one of those white labels with adhesive on the back that you would write on with a sharpie and then stick on anything from paper envelopes to filing drawers to tool shelves.

I am starting to wonder if that label started to disintegrate in the fuel tank or if the adhesive became some kind of gum and clogged part of my fuel injection system.

I bring that to light because when we pulled some of the injectors on Thursday, at least at first glance to me, it looked like the fuel injectors had some milky/gray liquid on the tip of the injectors. I could be wrong, I may have been really exhausted, and the light may have played tricks with my eyes, but I am pretty sure the tips of the injectors had a gray/milky/white liquid on the tips of them.

I don't know about that theory though, as two people were looking at the injector spray patterns and they said the injector spray patterns for cylinders 1 through 4 were good. I didn't see the patterns with my own eyes though (was busy jumping the RPM relay) ...

[Ron]

3. I did experiment with pulling spark plug wires off of cylinder 1 and 2 just to see what would happen. Last I recall from Thursday, there didn't seem to be any massive change when spark plug wires were taken off of 1 or 2. I could "hear" a difference as the plug wires were being slipped back on their respective plugs, but it was very, very minimal. I would almost say if you weren't listening for the change, you wouldn't have even known a plug wire had been pulled.

I need to take videos of the car idling. It is unbelieveable how bad yet clear the misfire is.This all sounds normal.
You need to use a hand held tachometer to detect subtle differences. What you are looking for is a cylinder that does not have the same drop in RPM when you pull its wire, side-by-side cylinders have a miss, they all act the same, the miss location is random, a cylinder that hits but drops less than others...too many to list. The info can point you to the cylinder with a problem (may help isolate air leak/valve problem, or, tell you the problem is in another system such as the ignition/air/fuel...).

I doubt the sticker/glue would harm anything...just too little of it and there is a screen and a filter...

When you were in the tank, did you specifically look for water?

[DeLorean03]

This all sounds normal.
You need to use a hand held tachometer to detect subtle differences. What you are looking for is a cylinder that does not have the same drop in RPM when you pull its wire, side-by-side cylinders have a miss, they all act the same, the miss location is random, a cylinder that hits but drops less than others...too many to list. The info can point you to the cylinder with a problem (may help isolate air leak/valve problem, or, tell you the problem is in another system such as the ignition/air/fuel...).

I doubt the sticker/glue would harm anything...just too little of it and there is a screen and a filter...

When you were in the tank, did you specifically look for water?

Where do you get a hand held tach and how do you go about hooking it up to the car to measure the differences (new territory, just learning as I go here) ?

As for water, honestly I did not - some people are wondering as well if I may have a huge amount of water in the tank, but honestly, I wouldn't know what water in the tank would look like.... ?

[Delorean02378]

The Title of this thread reminds me of this...


Kirk

[Kenny_Z]

When we spoke on the phone you said you didn't have a timing light. Here's a handheld tach/timing light combo. I recently bought one and I really like it. It's much more accurate than what you'd find in any stock car. http://www.sears.com/craftsman-professional-digital-timing-light/p-00914066000P?prdNo=1&blockNo=1&blockType=G1

If you purchase it in the store make sure to ask them to check the price of the online store. In the store this was a 100 dollar light but I lucked out and caught it during an online sale so I only paid 85.

[Ron]

Where do you get a hand held tach and how do you go about hooking it up to the car to measure the differences (new territory, just learning as I go here) ?
You can get a hand held at most any place that has auto parts (it don't need to be expensive. Shop around. You may be able to rent/borrow one from AutoZone or O'Reillys). Basically, you hook one lead to ground (the engine block) and the other to the terminal marked (-) on the coil. Warm the engine
and pull one plug wire at a time. When you pull a wire, place its end where the spark will jump to the block. If you don't see a spark, you will probably hear it jumping somewhere else (a bad spot in the wire, back at the coil if you hold it too far away, or not at all if it jumps to another wire or it has a very short jump). Record the RPM for each wire. Sometimes you can set the idle high manually to make the miss more pronounced (try several starting points anyway). Allow it to settle a few seconds before and after pulling or replacing each, then record. As an example, say your RPM was 750 and when you pulled #1 it went to 650, but #2 thru #6 it went to 600. That would match the idea of a burnt/sticky valve, air leak (to just that cylinder), crappy injector, etc since they all hit but one (#1) dropped less than the others...it is contributing, but not full power. From there you would do other tests to determine which (#1 cylinder's valves, the o-ring sealing the intake to that cylinder #1, injector #1, etc. Now, if they all dropped about the same amount, it would indicate a random miss, which points to something like an air leak that gets to all of the cylinders, a fuel delivery problem, etc (might be hard to see on an odd fire, but you may see a few that drop the same RPM but fluctuate more/just won't settle,....
All very basic and just a few scenarios with different clues.

If you suspect a certain thing, often you can eliminate/prove it by swapping parts (eg an injector, swap two, line and all, and see if the problem follows the part you moved.)

Double check your specs, then move to the test people have suggested and report back...someone here will usually spot the problem.

Edit:
Disable Idle Speed Motor, turn off all accessories

[Bitsyncmaster]

You can get a hand held at most any place that has auto parts (it don't need to be expensive. Shop around. You may be able to rent/borrow one from AutoZone or O'Reillys). Basically, you hook one lead to ground (the engine block) and the other to the terminal marked (-) on the coil. Warm the engine and pull one plug wire at a time. When you pull a wire, place its end where the spark will jump to the block. If you don't see a spark, you will probably hear it jumping somewhere else (a bad spot in the wire, back at the coil if you hold it too far away, or not at all if it jumps to another wire or it has a very short jump). Record the RPM for each wire. Sometimes you can set the idle high manually to make the miss more pronounced (try several starting points anyway). Allow it to settle a few seconds before and after pulling or replacing each, then record. As an example, say your RPM was 750 and when you pulled #1 it went to 650, but #2 thru #6 it went to 600. That would match the idea of a burnt/sticky valve, air leak (to just that cylinder), crappy injector, etc since they all hit but one (#1) dropped less than the others...it is contributing, but not full power. From there you would do other tests to determine which (#1 cylinder's valves, the o-ring sealing the intake to that cylinder #1, injector #1, etc. Now, if they all dropped about the same amount, it would indicate a random miss, which points to something like an air leak that gets to all of the cylinders, a fuel delivery problem, etc (might be hard to see on an odd fire, but you may see a few that drop the same RPM but fluctuate more/just won't settle,....
All very basic and just a few scenarios with different clues.

If you suspect a certain thing, often you can eliminate/prove it by swapping parts (eg an injector, swap two, line and all, and see if the problem follows the part you moved.)

Double check your specs, then move to the test people have suggested and report back...someone here will usually spot the problem.

If your idle system is working the RPMs should hold at 750 with that test. What you could do it let the engine heat up first and then pull the connector off the idle motor.

[Ron]

GOOD POINT! Actually on a D it would drop then the ISM would try to bring it right back.
THX!

[DeLorean03]

Great stuff guys! I'll get the combo light Kenny linked and try to have some results by Thursday night. Ken Koncelik thinks it's an injector problem based on the description of everything I gave him. He has 6 new injectors, so we'll swap them and see what happens. I'll keep everyone in the loop, and I'll take a video for reference and posterity purposes so when someone else has this problem down the road, they can watch the video and verify "Yep, that's what my car is doing......now how did you fix it...?"

Will update this thread accordingly!

[thirdmanj]

http://img.tapatalk.com/d/13/05/12/ryranupa.jpg

Sorry.. Chris posted it on FB, I couldn't help but think of this thread.

[Dangermouse]

I think post 25 is why Chris posted it on FB :)

[thirdmanj]

I think post 25 is why Chris posted it on FB :)

My god I suck. :banghead:

[Nicholas R]

Where do you get a hand held tach and how do you go about hooking it up to the car to measure the differences (new territory, just learning as I go here) ?

The Opel has an aftermarket tach hooked up to it right now. You can use it. Its under the hood. Red wire to hot, black to ground, and green to the negative side of the coil. Also make sure the switch is set to 6 cylinders (currently it's set to 4).

I'll be there Thursday too.

Depending on the RPM range and engine loading that the miss occurs, I say either coil or injectors. Weak spark or poorly ionized fuel.

[DeLorean03]

Awesome!!! I'm glad I didn't miss you heading to Florida! I was really bummed missing the cruise you guys had, but Jessica's graduation was very important to me. Look forward to seeing you on Thursday! Hopefully it'll be something simple!

I'll use the tach for sure, and I'll prolly be buying that one st Sears that is a ign light/tach combo. Just add more and more awesome tools in my garage!


The Opel has an aftermarket tach hooked up to it right now. You can use it. Its under the hood. Red wire to hot, black to ground, and green to the negative side of the coil. Also make sure the switch is set to 6 cylinders (currently it's set to 4).

I'll be there Thursday too.

Depending on the RPM range and engine loading that the miss occurs, I say either coil or injectors. Weak spark or poorly ionized fuel.

[DeLorean03]

You can get a hand held at most any place that has auto parts (it don't need to be expensive. Shop around. You may be able to rent/borrow one from AutoZone or O'Reillys). Basically, you hook one lead to ground (the engine block) and the other to the terminal marked (-) on the coil.


Red wire to hot, black to ground, and green to the negative side of the coil.



Hey guys, just curious - is there a reason that these two steps differ? Ron, was it assumed in your instructions that red went to hot, or are there hand-held tachs with only 2 wire leads.... ?

Just want to make sure I know how to do this 100% when I go to my car on Thursday.

[Ron]

Ron, was it assumed in your instructions that red went to hot, or are there hand-held tachs with only 2 wire leads.... ?

The ones with two wires don't need one to "hot" (unless you are measuring volts) as in this example (http://www.ebay.com/itm/Actron-Ignition-Tester-Dwell-Meter-Tachometer-Voltmeter-Ea-CP7605-Used-/181136330383?pt=Motors_Automotive_Tools&hash=item2a2c910e8f&vxp=mtr).
(Not a bad deal, so far, since it has analog dwell ;-)

[David T]

If you can figure out which cylinder is misfiring I would swap the fuel injector and see if you can move the trouble to another cylinder. I am still thinking it is a dirty injector. It is not easy to properly assess the spray pattern on the car. If you hear knocking in the valve cover you probably need to adjust a valve or 2. I would do that before anything else.
David Teitelbaum

[DeLorean03]

I am still thinking it is a dirty injector. It is not easy to properly assess the spray pattern on the car. If you hear knocking in the valve cover you probably need to adjust a valve or 2. I would do that before anything else.
David Teitelbaum

This is just about becoming the overall consensus. You, David-DMCMW, Casey (DMCHillbilly), Ken Koncelik, Nick, and others strongly believe this. I sure hope that's all it is. Ken's got 6 new injectors waiting for me; we will see soon.

[DMCMW Dave]

This is about where you find the loose plug wire........

[Mike C.]

This is about where you find the loose plug wire........

:biggrin:

[DeLorean03]

This is about where you find the loose plug wire........

Been there, done that ): ...

It is nearly left to a bad injector. We'll see soon. If it is a bad injector, I'll be adjusting my valves by means of a feeler tool if I hear any knocking when the engine gets warm.

When you hook up the CIS fuel pressure gauges, you are measuring the pressuer from the fuel distributor to the control pressure regulator, correct? My fuel pressure (system pressure) was at about 75 PSI (going by memory here). If the fuel distributor was faulty, wouldn't the perssure be much lower? I ask because I'm trying to rule out a bad fuel ditributor and go towards concluding to a bad injector.

[Doogie]

:biggrin:
This is about where you find the loose plug wire........

:biggrin: I'll be there too Thursday. Although I agree with most about the injectors, (we never did get the front 2 on the drivers side checked!) I still want to look under the valve cover on the passenger side. Seems awfully noisy after it warmed up over there!

[DeLorean03]

:biggrin:

:biggrin: I'll be there too Thursday. Although I agree with most about the injectors, (we never did get the front 2 on the drivers side checked!) I still want to look under the valve cover on the passenger side. Seems awfully noisy after it warmed up over there!

We will.

All 6 injectors are being replaced in one shot. Whatever I owe Ken for that is what I'll be paying for them. Man, if that's all it is, I'll be so happy :biggrin:.

[NightFlyer]

Best of luck - hoping for the best!

[jawn101]

We will.

All 6 injectors are being replaced in one shot. Whatever I owe Ken for that is what I'll be paying for them. Man, if that's all it is, I'll be so happy :biggrin:.

Pulling for ya on this... It's always the last thing you try... :)

[Ron]

Been there, done that ): ...

It is nearly left to a bad injector. We'll see soon. If it is a bad injector, I'll be adjusting my valves by means of a feeler tool if I hear any knocking when the engine gets warm.

When you hook up the CIS fuel pressure gauges, you are measuring the pressuer from the fuel distributor to the control pressure regulator, correct? My fuel pressure (system pressure) was at about 75 PSI (going by memory here). If the fuel distributor was faulty, wouldn't the perssure be much lower? I ask because I'm trying to rule out a bad fuel ditributor and go towards concluding to a bad injector.
When the valve on the gauge between the CPR and the gauge is open, you are measuring the pressure from the CPR to the FD (Control Pressure). When you shut the valve (preventing the CPR from dumping fuel/pressure), you are measuring pressure from the FD (actually the PPR inside it, from the undisturbed line) to the CPR (Primary Pressure). Shut the engine off and you are measuring Rest Pressure...

Basically, if the FD was faulty, the pressure distributed to the injectors could be high, low, or both (or cause a lot of other pressure problems depending...)

FYI, it doesn't matter which line from the FD goes to which cylinder like it does with the ignition distributor...you can swap them around to try and locate the cause of the miss....

=====

Hang in there!
I predict you will have it running well soon, sporting 6 new injectors...whether you figure out exactly what was causing it or not...
J/K :deviltail:

[DeLorean03]

So here is where we are:


http://www.youtube.com/watch?v=xn0VF0lsxWw&feature=youtu.be

I installed the three injectors on the passenger side. No improvement. Tomorrow, I'll be installing injectors on the driver's side as well as a new cap, rotor, and ignition coil. I'll keep everyone in the loop as to how things go.

Oh, the car died in the video because the return line to the pump blew off the metal fuel line - just in case you were wondering. I reattached it, and it was not the source of the problem (fuel pressure).

[jawn101]

Hang in there man.

[DeLorean03]

Also, the ignition timing light/tachometer I purchased has a setting for "2 cycle" or "4 cycle" - does anyone know what the proper setting is for our cars? Thanks!

This is the one I bought:

http://www.sears.com/craftsman-professional-digital-timing-light/p-00914066000P

[jawn101]

Also, the ignition timing light/tachometer I purchased has a setting for "2 cycle" or "4 cycle" - does anyone know what the proper setting is for our cars? Thanks!

This is the one I bought:

http://www.sears.com/craftsman-professional-digital-timing-light/p-00914066000P

Should be 4 cycle for anything other than like a lawn mower or an outboard.

[DeLorean03]

Should be 4 cycle for anything other than like a lawn mower or an outboard.

Thank you, sir!

[Nicholas R]

Even most lawnmowers now are 4-cycle. Only weed eaters and blowers and maybe like those little motorized scooters are 2-cycle now.

[refugeefromcalif]

Only weed eaters and blowers and maybe like those little motorized scooters are 2-cycle now.

My Troy Bilt weed eater is 4 cycle/stroke. (I got tired of mixing gas). :)

George

[DeLorean03]

6 new fuel injectors installed. No change.

[David T]

Get a voltmeter and measure the system voltage when the motor is off and when it is running.
David Teitelbaum

[DeLorean03]

Get a voltmeter and measure the system voltage when the motor is off and when it is running.
David Teitelbaum

Where and how?

[Ron]

Did you try pulling the plug wires one at a time to see if one does not add a miss (or change the existing one)?

EDIT: David is off line... I think he meant to take both measurements right off of the battery. If you are seeing something like 12.x V off and 14.2+ running you are OK.
You could check at the coil (+) and ground to be sure the ignition is being fed correctly...

[DeLorean03]

Just wanted to check in with everyone. It seems we have fixed the problem. It was either a bad cap or rotor. We changed both, and the car idles and drives great.

Man, what an issue that was. Glad that's over!

[Kenny_Z]

Awesome, glad to see you resolved it. That was a lot of work for a cheap and semi-easy part to replace. You must be a fuel distributor removal expert now.

[NightFlyer]

Just wanted to check in with everyone. It seems we have fixed the problem. It was either a bad cap or rotor. We changed both, and the car idles and drives great.

First off, glad that you finally have the problem identified and rectified. :bigclap:
Second, didn't I tell you to try changing the cap and rotor from the get go?


What you describe in terms of engine behavior sounds like an ignition problem. I'd start by checking or changing the plugs, wires, cap, and rotor. (emphasis added)

Yep, I sure did! :slap:

Always do the simple cheap stuff FIRST. Honestly, you could have saved all that time, effort, and money you spent fooling around with the fuel injectors!

Oh well, live and learn!:thumbup:

[DeLorean03]

Awesome, glad to see you resolved it. That was a lot of work for a cheap and semi-easy part to replace. You must be a fuel distributor removal expert now.

I'm decent when it comes to removing the fuel mixture unit - no doubt o_O ....



First off, glad that you finally have the problem identified and rectified. :bigclap:
Second, didn't I tell you to try changing the cap and rotor from the get go?

(emphasis added)

Yep, I sure did! :slap:

Always do the simple cheap stuff FIRST. Honestly, you could have saved all that time, effort, and money you spent fooling around with the fuel injectors!

Oh well, live and learn!:thumbup:

Yes you did. I'll say this - to me -removing the injectors was a bit easier than taking the mixture unit off ;). But yes, credit to where it's due. I sure did learn a HECK of a lot through this last 8 days. I never even opened my new digital timing light. That's $100 I think I'll get back at Sears tomorrow :biggrin: .

THEN again.......this would be an excellent time to now see how the timing light/tach works on a properly running DeLorean.

[Nicholas R]

Yes you did. I'll say this - to me -removing the injectors was a bit easier than taking the mixture unit off ;).

I agree. Injectors can be out in 5 minutes with new ones in in another 5. 20 minute round trip job at the most.

Cap and rotor is a commitment; lots more involved in order to gain access. :wrenchin:

[David T]

If you do the cap and rotor you typically also do the spark plugs and wires. A bad cap (or rotor) would have been found by pulling a wire, one at a time, from each spark plug and watching for a drop in RPM. Or possibly a blue glow or the sound of arcing. You "shotgunned" it and got lucky.
David Teitelbaum

[DeLorean03]

If you do the cap and rotor you typically also do the spark plugs and wires. A bad cap (or rotor) would have been found by pulling a wire, one at a time, from each spark plug and watching for a drop in RPM. Or possibly a blue glow or the sound of arcing. You "shotgunned" it and got lucky.
David Teitelbaum

Based on the things I did, I respectfully disagree. Compression was good, fuel pressures were good, injectors were changed, and plugs and plug wires were good. Only thing left (in my mind) was the cap and rotor.

Bottom line, I sure hope this thread benefits the community and that anyone with the issue I was having will stumble upon it. Thank you everyone for your help!

[NightFlyer]

If you do the cap and rotor you typically also do the spark plugs and wires. A bad cap (or rotor) would have been found by pulling a wire, one at a time, from each spark plug and watching for a drop in RPM. Or possibly a blue glow or the sound of arcing. You "shotgunned" it and got lucky.
David Teitelbaum

Not really shotgunning it - based on the problem described, and the checks / trouble-shooting already performed, nearly everyone had initially diagnosed the issue as being ignition related. Easiest way to troubleshoot ignition related problems is to start at the plugs and work your way back, as most of the system is made-up of wear items requiring regular part changes anyway.

The cap and rotor are regular maintenance items, requiring a regular change to keep the engine functioning at its optimal performance. Obviously, DeLorean03's cap and rotor were definitely overdue for a change.

But if you're still convinced that it was a shotgun approach, I'd personally rather shotgun it on a regular maintenance item such as the cap and rotor as opposed to a non-regular maintenance item such as the fuel injectors.