4.3L Misfire

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Thread: 4.3L Misfire

  1. #1
    Walking
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    4.3L Misfire

    Hi guys, new here and in search of my never ending problem. I have a 96 s10 4.3 vin X 5spd. The problem I am chasing is a misfire and cruising at steady speeds. Its not there much at idle or WOT..Never the less the problem seems worst when the truck is cold.
    I've done a full tune up on it, plugs, wires, cap, rotor. I've also replaced the EGR valve because I am getting an EGR position P1406 at times. I did a temperary block off to make sure I wasnt getting any bypass EGR gasses that could cause my problem. I replaced the intake gaskets due to leaking and all this has got me no where but upset and broke.

    I did find that my coil was arcing, so I went and got a replacement ACDelco coil...Thinking I had solved my problem I took it on a drive. NO CHANGE. Later that night I checked the ignition system again only to find that my new coil is arcing in the exact same way the old one was.






    I've hooked up a tech2 to it and watched the sensors, even manually operated some of them. The only one that makes me question what it is doing is the TPS % bounces with the truck running, anywhere from 8%-0%, but with the key on engine off I can hold it at a steady 8%

    Anyone know of a solution to my arcing?????

    thanks,
    Jeff

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    4.4 Liter Supercharged Northstar bouda's Avatar
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    Re: 4.3L Misfire

    Man it's odd that the coil arches like that, even after changing it. I'd take it back and get a new one if at all possible. Wish I could help more. If it's not that maybe it's the distributer itself, or the ignition module.

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    4.4 Liter Supercharged Northstar Tomko's Avatar
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    Re: 4.3L Misfire

    Quote Originally Posted by S10asmyDD
    I've done a full tune up on it, plugs, wires, cap, rotor. .. I did find that my coil was arcing, so I went and got a replacement ACDelco coil...

    Anyone know of a solution to my arcing?????

    thanks,
    Jeff
    My neighbor had a similar arcing problem with a 4.3 in an Astro van. He had upgraded his ignition with aftermarket crap. His fix was to replace everything with dealer supplied AC Delco parts. Then it worked.

    Given all of the work that you've done, is it possible - just possible - that one of the wires has been crossed or mis-routed? I know this must be a darn frustrating thing for you, but the problem could be something so basic and routine that both you and the Tech 2 aren't picking up on it.

    BTW, I'd love to hear how you got your hands on a Tech 2...
    Tomko

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    4.4 Liter Supercharged Northstar bouda's Avatar
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    Re: 4.3L Misfire

    Yeah, it wouldn't hurt to check the wires. I've changed them a million times and I still always mess it up. How bad is it missing? Just a little miss here and there, or does it shake like hell?

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    Walking
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    Re: 4.3L Misfire

    It will shake like hell, but only sometimes.. In the afternoon I may get in and ride all the way home with out a problem. Although this was not the case friday. Missed like hell almost all the way home. Sometimes shutting it down and restarting it will make the problem go away, but not allways. This still doesn't explain why my coil is arcing like it is.....

    Im almost leaning twards the ECM, but I can't prove to myself that its the problem. However it would regulate the voltage to the coil wouldn't it?

    We have a tech2 at work (Freightliner and Izusu dealership) for working on the 6.0L gm engines. It has the izusu hombre program for the 4.3...

    As far as my ignition components. Everything is AcDelco with the exception of the cap and rotor.
    Last edited by S10asmyDD; 08-13-2006 at 05:51 PM.

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    2.4 Liter SIDI ECOTEC ockgator's Avatar
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    Re: 4.3L Misfire

    The "arcing" you mention is probably whats called "corona discharge", it's the EMI around the coil and wires interacting with the moisture in the air.
    EGR codes are common for this engine, the pintle gets a piece of crud in it and sticks open, sometimes it clears itself out but usually you have to take the valve off and clean it. Also sometimes the pintle will stick at full EGR, in this case you must pull it and using a good injector cleaner get the crud off the pintle shaft, it has a fairly weak return spring.
    26yr veteran or the underhood wars, 13 at chevy dealer
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    Re: 4.3L Misfire

    Well I broke down and took it in today since I'm at a loss and don't have enough time to spend hours on the tech2...They said it drove fine without any mis in it today. I told them to keep it for a couple days, I haven't had a morning that the truck hasn't missed in who knows how long.

    Maybe its just mad at me?

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    4.4 Liter Supercharged Northstar bouda's Avatar
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    Re: 4.3L Misfire

    Intermentint(SP?) problems are the hardest to diagnose.

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    6.0 Liter L76 V8 tom3's Avatar
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    Re: 4.3L Misfire

    Quite often a light throttle miss is a dirty injector, or a vacuum leak somewhere. Keep us posted at what they find.

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    Re: 4.3L Misfire

    Well, the shop I took it to were completely unwilling to try to find the problem. When I got the truck back it had no more than half a mile on it from when I dropped it off, and I didnt make it out of their parking lot without it missing. So now its at a diffrent place that will hopefully take care of there customers. I should have known they didn't do much when they told me there was no charge..GRRR..

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    Re: 4.3L Misfire

    Sorry its been awhile...I've been busy. Heres an update.

    Found that the truck was one tooth advanced on the distributor. That got rid of my missfires, except I am constantly fighting a P1406. Its got a brand new EGR valve, and from what work I have done to try and find the problem this far it has no obvious broken or damaged wires.

    Here is the freezeframe the tech2 gave me about the last 1406.

    Engine speed 1531 RPM
    Ect 188*F
    Map 25kPa
    short term FT bank1 -3%
    short term FT bank1 124 count
    long term FT bank1 -10%
    long term FT bank1 114 count
    Short term FT bank2 -3%
    short term FT bank2 124 count
    Long term FT bank2 -13%
    Long term FT bank2 111count
    Loop status Closed Loop
    Engine Load 5%
    MAF 10.91g/s
    speed 49mph

    Does this info seem usefull in finding the problem or is it just a bunch of fuel trim jibberish that aint worth a darn with EGR problems? If I clear the code from the ECM..Almost on the DOT 5 days later the damn thing will come back....
    Last edited by S10asmyDD; 09-23-2006 at 07:10 PM.

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    Re: 4.3L Misfire

    There was a reflash for the engine control module for a P1406. You'll need to take it to a dealer or a shop capable of checking the existing programming. Here is a partial print of the DSB explaining the reflash.

    MALFUNCTION INDICATOR LIGHT (MIL) ON, POOR DRIVEABILITY #76-65-04 - (Mar 3, 1997)

    SUBJECT: MALFUNCTION INDICATOR LIGHT (MIL) ON, POOR DRIVEABILITY CONDITIONS (PERFORM FLASH CALIBRATION)

    MODELS: 1996-97 CHEVROLET AND GMC LIGHT DUTY TRUCKS 1996-97 CHEVROLET TILTMASTER AND GMC FORWARD W4 MODELS 1996-97 OLDSMOBILE BRAVADA WITH 4.3L, 5.0L, 5.7L ENGINES (VINS X, W, M, R - RPOS LF6, L35, L30, L31)

    CONDITION:

    AN OWNER MAY REPORT THAT THE MALFUNCTION INDICATOR LIGHT (MIL) IS ON AND/OR THE VEHICLE HAS ONE OR MORE OF THE FOLLOWING DRIVEABILITY CONDITIONS.
    1. 5.7L (L31) ONLY: SURGE OR CHUGGLE AT SPEEDS OF 42 TO 65 MPH WHILE AT STEADY SPEED OR UNDER LIGHT TO MODERATE ACCELERATION WITH THE TCC APPLIED.
    2. MIL ON WITH DTC P0172 OR P0175 STORED BUT NO REPORTED DRIVEABILITY SYMPTOMS.
    3. MIL ON WITH DTC P1406 STORED AND ROUGH ENGINE OR POOR DRIVEABILITY SYMPTOMS.
    4. WHEN OPERATING AT ALTITUDES ABOVE 5,000 FEET, AN AUDIBLE SPARK KNOCK NOISE IS HEARD.
    5. HESITATION AND/OR MISFIRE DURING LIGHT CRUISE CONDITIONS DUE TO IGNITION CROSS-FIRE WITH NO DTC STORED. THIS WILL ONLY OCCUR ON V-6 ENGINES WITH CAM RETARD OFFSET IN EXCESS OF 26 DEGREES AND V-8'S WITH CAM RETARD OFFSET IN EXCESS OF 15 DEGREES.
    6. THE MIL MAY BE ON AND A DTC STORED FOR AN ENGINE MISFIRE BUT NO MISFIRE OCCURRED.
    7. ENGINE EXHIBITS AN IDLE SPEED SURGE OR ROLL.
    1996 MODELS ONLY
    8. MIL ON WITH DTC P0102 STORED BUT NO REPORTED DRIVEABILITY SYMPTOMS.
    9. 5.0L (L30) + 5.7L (L31) ONLY: DIFFICULT STARTING IN EXTREME COLD (BELOW 0 DEGREES F) CONDITIONS.
    10. 5.7L (L31) ONLY: POORER THAN EXPECTED FUEL ECONOMY WHEN HEAVILY LOADED

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