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Thread: Uh oh ....

  1. #11
    Vin3299's Doc DeLorean03's Avatar
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    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....
    DMCTalk.org Moderator

    Actual snippet of a conversation from Sept 2013:

    Me: Eddie, I can't wait to get the car back when you're done with it.

    Eddie: Yeah, you'll be able to give the car gas, and it won't be - like - embarrassing....

  2. #12
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    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?
    Last edited by NightFlyer; 05-09-2013 at 06:02 PM.

  3. #13
    Senior Member Silverbullet's Avatar
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    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...

  4. #14
    Senior Member Bitsyncmaster's Avatar
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    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.
    Dave M vin 03572
    http://dm-eng.weebly.com/

  5. #15
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    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

  6. #16
    Vin3299's Doc DeLorean03's Avatar
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    Quote Originally Posted by NightFlyer View Post
    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.

    Quote Originally Posted by Silverbullet View Post
    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.

    Quote Originally Posted by Bitsyncmaster View Post
    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.
    Quote Originally Posted by David T View Post
    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.

    Quote Originally Posted by David T View Post
    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" ?
    DMCTalk.org Moderator

    Actual snippet of a conversation from Sept 2013:

    Me: Eddie, I can't wait to get the car back when you're done with it.

    Eddie: Yeah, you'll be able to give the car gas, and it won't be - like - embarrassing....

  7. #17
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    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!

  8. #18
    DMC Midwest - 815.459.6439 DMCMW Dave's Avatar
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    Quote Originally Posted by DeLorean03 View Post
    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.
    Dave S
    DMC Midwest - retired but helping
    Greenville SC

  9. #19
    Administrator Ron's Avatar
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    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... )

  10. #20
    Vin3299's Doc DeLorean03's Avatar
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    Quote Originally Posted by NightFlyer View Post
    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.

    Quote Originally Posted by DMCMW Dave View Post
    Run the engine in the dark and look at it.
    I love the simple explanations (: !

    Quote Originally Posted by Ron View Post
    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.
    DMCTalk.org Moderator

    Actual snippet of a conversation from Sept 2013:

    Me: Eddie, I can't wait to get the car back when you're done with it.

    Eddie: Yeah, you'll be able to give the car gas, and it won't be - like - embarrassing....

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