Uh oh ....

[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-profe...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!