The Advanced Complicated Mysterious Engine Misfire Story

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  • #1

    The Advanced Complicated Mysterious Engine Misfire Story

    Here she goes!

    First off… let me let you guys know.
    Car before was running perfect (About 1 month ago), It has a Brand new OEM Nissan Distributor Cap, New OEM Nissan Ignition Rotor, Brand New Nissan spark plug wires, which are all about 4-6 months old, It also has NGK Standard Spark Plugs (Just about New).+

    Also I got a GREAT deal on a Re-manufactured Distributor with Crank angle sensor from Autozone, made by I BELIEVE wells(company name), which I have installed about 1 month ago.

    Everything is working SEAMLESSLY in my ignition system, CRISP idle, perfect driveability.

    Fastforward 3 months (Which was one month ago).
    I was bored and decided to take off the spark plug wires off the distributor cap ONLY, and decided to squirt a ton of Di-Electric Grease in there. The reason you may ask? … well… I was bored.
    I then took off the "power source 2 wire plug" going to the ignition coil, and decided to squirt some Di-Electric Grease in there as well, and while I was there I have "shortened" that wire, by cutting the plug off, cutting off the excess wire, and then using "crimp" connectors to re-attach it throwing away the excess wire.

    I finally did all that and started the car.
    BAM!
    Horrible engine miss! :-(
    So I took her to firehawks shop.
    Ignition timing (perfect 15 degrees) (Didnt change anything to fixing the problem)
    Changed spark plugs AGAIN using standard Nissan NGK's (Didnt change anything to fixing the problem)
    Used a Brand spanking new Distributor cap, and cleaned the "new" wires I had (cleaned out the di-electric grease I put in there previously, which was a ton!) (Didnt change anything to fixing the problem)

    So the LAST thing there were, are the spark plug wires, so I borrowed a BRAND NEW set and put them on… (Didnt change anything to fixing the problem)

    Ok. So now Im stuck.
    Firehawk checked the ignition coil, and it measured within spec, but we replaced it from a good running car to see if that was the problem.
    (Didnt change anything to fixing the problem)

    So FINALLY We took off the 2 power wires that I have cut and shortened goign to the ignition coil, and chuck connected them professionally.

    Ok.
    So now im lost.


    Now before you guys start saying things!, listen to this:
    The engine miss is ONLY at idle, and ONLY at "heavier" engine loads at LOW rpm.

    But theres another thing.
    The engine miss ISNT random!
    It has a RYTHYM!
    it goes through the EXACT SAME rythym every 2-3 minutes,
    … for 20 seconds it will idle at 1k rpms but miss a bunch, and every time it "misses", the engine rpm will drop slightly, after this it goes in to a "idle at 700rpms pretty good but miss a bit", and then after this "rythym" it will go to a "idle at 4-500 rpms and want to die" rythym, and then it starts ALL over again and goes back to the first rhytym.


    Cold start is PERFECT (Only in the mornings after car has sat for over 7-8 hours)
    Car idles CRISPY smooth! and runs GOOD!
    But this only lasts for about 4-5 minutes.
    After it warms up, it goes right back to that "ryhthymic" engine miss like im describing earlier in the thread.


    This does sound weird, but hey… I dont know what else to do!!!


    Only when I messed with the car it started to miss… but the thing is, I have already 'reversed' my steps backwards and put on new parts and its STILL doing it!
    It does not have any     noticeable misses from 2500rpms and up.


    Car has NO EMISSIONS, and only has the items that are required to run the car (distributor, CHTS, MAF, TPS etc…)


    HELP!
    1SIKZ31 -86 SlickTop- R.I.P. 03/01/10 … Parted out :-(
    … New Project: LS1 Miata. Complete. 510whp. 2500lbs.
    1 Month Away from Rear Mount 76 --> 650-700whp.
  • #2
    Re: The Advanced & Complicated Mysterious Engine Misfire Story

    You forgot to mention that redoing the connection to the coil fixed it, but it came back a few days later. Also, the power transitor connector was cut out and spliced so it can't be easily checked.
    Chuck Stong
    300+ Parts and Performance owner
    http://www.300-plus.com
    2002 ZCOT president and always active member
  • #3
    Re: The Advanced & Complicated Mysterious Engine Misfire Story

    Firehawk wrote: You forgot to mention that redoing the connection to the coil fixed it, but it came back a few days later. Also, the power transitor connector was cut out and spliced so it can't be easily checked.



    actually, whenever we did that (re-spliced and fixed coil power connection), it did     appear to be ok, but it was only because it was one of those periods where the car ran "ok". 2 minutes after this it started to do it again, but I didnt say anything since you were busy doing things in the shop.

    So now Ive boiled the problem down to being an electrical problem, and the only reason for that is because the engine miss isnt "random", it actually has a "pattern to it".


    Wow. No one replied. thats nice. :nanan?re
    1SIKZ31 -86 SlickTop- R.I.P. 03/01/10 … Parted out :-(
    … New Project: LS1 Miata. Complete. 510whp. 2500lbs.
    1 Month Away from Rear Mount 76 --> 650-700whp.
  • #4
    Re: The Advanced & Complicated Mysterious Engine Misfire Story

    open exhaust? open at cat or back of turbo?

    Pattern doesn't mean its electrical.. mechanical timing and combustion is also pattern based.

    When i ran open exhaust from catback it had a pattern based miss at idle for years. exact pattern miss

    My close friend had open exhaust off turbo and had the same idle miss for years.exact pattern miss

    the damn computer is like an atari compared to new computers or xbox lol


    Everyone talks about bad idle with larger injectors, but when i went larger on injectors and went with a standalone it became the smoothest running VG i've ever felt.
    Praying....
  • #5
    Re: The Advanced & Complicated Mysterious Engine Misfire Story

    No the dielectric grease didnt get in to the CAS.

    I never knew that 1sickz, good information!
    Yes open turbo after the downpipe (Basically where the car is)

    Its a thing that just recently started though, im pretty sure its either the power transistor, the CAS, and thats all I can think of for now.

    Any other pointers? :-?
    1SIKZ31 -86 SlickTop- R.I.P. 03/01/10 … Parted out :-(
    … New Project: LS1 Miata. Complete. 510whp. 2500lbs.
    1 Month Away from Rear Mount 76 --> 650-700whp.
  • #6
    Re: The Advanced & Complicated Mysterious Engine Misfire Story

    Yes. Learn to solder, it is very easy. NO CRIMP CONNECTORS for important things that are timed down to the millisecond.

    Terrible idea putting those wheels on…
  • #7
    Re: The Advanced & Complicated Mysterious Engine Misfire Story

    1SIKZ31 wrote: No the dielectric grease didnt get in to the CAS.

    I never knew that 1sickz, good information!
    Yes open turbo after the downpipe (Basically where the car is)

    Its a thing that just recently started though, im pretty sure its either the power transistor, the CAS, and thats all I can think of for now.

    Any other pointers? :-?
    If it was the CAS you would have the same pattern through out all rpm range and load ranges. it wouldn't go away.

    How many miles on the motor?
    Praying....
  • #8
    Re: The Advanced & Complicated Mysterious Engine Misfire Story

    do a compression test. You might have something melted or broken.
    86 hardtop shell, 93 SC300 engine, 95 soarer bellhousing, 91 supra transmission, 95 Q45 differential hubs and driver's side axle, 1992 300ZX turbo driver side axle and calipers, 2004 350Z Rotors, 87 300ZX front end/hood, 1999 Viper radiator, 1992 Mustang throttle body. Lots of glue and tape to keep it all together.
  • #9
    Re: The Advanced & Complicated Mysterious Engine Misfire Story

    "Brand new" Rebuilt Long Block (VG30E) 9:1 Compression with almost 10 thousand miles on it.

    I guess Im going to solder those connections. To Check the "Power Transister" with a Multi-Meter, what wires Do I check and what should continuity be.

    I do know how to solder, I just didnt because I wasnt thinking actually how important those 2 wires really are.

    Im almost confident soldering them wont help anything though, my bets are on the transistor or the CAS even though its new (the cas is)
    1SIKZ31 -86 SlickTop- R.I.P. 03/01/10 … Parted out :-(
    … New Project: LS1 Miata. Complete. 510whp. 2500lbs.
    1 Month Away from Rear Mount 76 --> 650-700whp.
  • #10
    Re: The Advanced & Complicated Mysterious Engine Misfire Story

    anyone know if the early pathfinder pts would work? I have one kicking around (same plug)
  • #11
    Re: The Advanced & Complicated Mysterious Engine Misfire Story

    Soo…
    If the CAS isnt the problem…
    and the Ignition System is new…
    The ONLY thing left to check is the Power Transistor module.

    What should it measure when checking?
    1SIKZ31 -86 SlickTop- R.I.P. 03/01/10 … Parted out :-(
    … New Project: LS1 Miata. Complete. 510whp. 2500lbs.
    1 Month Away from Rear Mount 76 --> 650-700whp.
  • #12
    Re: The Advanced & Complicated Mysterious Engine Misfire Story

    Find a shop with an ignition scope and have them find out whether it's in the primary or the secondary. Also with a scope, graph the cas signal for irregularities.
    Check all your grounds, and maybe wiggle the chts connector, I've found corrosion build up inside that connector to appear very rapidly after replacement. Also check the maf ground and signal wires. As far as the power transistor, it's a simple switch......I would try a known good one as even if it checks out ok it could be intermittant with heat build up.
    Denis Gagné
    aka VGwagon
    GM specialized licensed technician

    69 510 VG30 powered wagon
    73 240z shell VG30et in progress
    86 300zx NA2T
  • #13
    Re: The Advanced & Complicated Mysterious Engine Misfire Story

    G-E wrote: anyone know if the early pathfinder pts would work? I have one kicking around (same plug)
    Yeah it works just fine, you might have to switch the wires around, I can't remember but I think I just plugged it in when I was running the early pathy manifold, now I'm running the 97 pathy intake and distributor with coil and PT built in, the spark seems much hotter than the old 85 zx and 92 pathy setup.
    Denis Gagné
    aka VGwagon
    GM specialized licensed technician

    69 510 VG30 powered wagon
    73 240z shell VG30et in progress
    86 300zx NA2T
  • #14
    Re: The Advanced & Complicated Mysterious Engine Misfire Story

    1SIKZ31 wrote: Soo…
    If the CAS isnt the problem…
    and the Ignition System is new…
    The ONLY thing left to check is the Power Transistor module.

    What should it measure when checking?
    Motor.
    Praying....
  • #15
    Re: The Advanced & Complicated Mysterious Engine Misfire Story

    It doesn't matter how many miles are on the engine, you could still have melted a piston. If you have low compression in one cylinder, it will run on 5 cylinders until you break into boost.

    A compression test is easy and quick, and will tell you a lot. Humor me.
    86 hardtop shell, 93 SC300 engine, 95 soarer bellhousing, 91 supra transmission, 95 Q45 differential hubs and driver's side axle, 1992 300ZX turbo driver side axle and calipers, 2004 350Z Rotors, 87 300ZX front end/hood, 1999 Viper radiator, 1992 Mustang throttle body. Lots of glue and tape to keep it all together.
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