Cylinder 4 not firing!
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Thread: Cylinder 4 not firing!

  1. #1
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    Cylinder 4 not firing!

    I have a 2001 VW Passat 1.8T AUG, that I have had for 5 years last week I replaced the camshaft tensioner , ones done and fired up the engine the car started miss fearing, after some time of scratching my head I fount that the harness that connect the coil pack was shorted on cylinder 4, 3, 2 the insulation had crumbled, and the coil on cylinder 4 had the secondary coil open, after replacing the coil, the car still miss fires. I am getting on the scanner, multiple miss fire, miss fire on cylinder 2 and 4. Cylinder 4 is not firing in the cylinder; I pulled the plug out and is wet with gas.

    Thing that I have check or replaced:

    Coils are getting 12v to Pin 4
    ECM is sending trigger signal to pin 2 and I am getting a spar on each spark plug when is out of the head
    The injectors are injection gas
    I have disconnected the ECM for long periods of time hoping that it will reset any errors that it may have.
    I have replace coil pack 2 and 4 with new ones
    I replace the Can positioning sensor
    Replace the spark plugs
    I pulled the plug out of cylinder 4 and let the cylinder dry over night to see if the jet is leaking gas, no leaks that I can see

    Can the ECM be damaged on Cylinder 4, or is there any time challenge that I donít now about.

    Need help!!

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  3. #2
    Moderate Moderator Steve in Chicago's Avatar
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    The engine ran fine until the cam chain tensioner was replaced and now it's misfiring? First double check to be sure the cams are in time. It's common for the cams to go back in one tooth off.

    If the ignition harness is crumbling and shorting, you can replace the section that runs on top of the valve cover by getting this harness and grafting in onto your engine. This harness is not plug-and-play on these engines but it does have all the connectors and wires needed to make your own replacement sub-harness.

    Home Page > Search > Coil Harness > ES#7679 Coil Pack Wiring Harness Replacement - 1J0971658L

    Here is the ATW ignition schematic. I think it's the same as the AUG ignition. Some of the wire colors may be different, so document your existing ignition wiring before cutting it off.

    http://www.audigeeks.com/images/tech...tronic_ATW.jpg

    I have one of these harnesses new in the box, never used. $35 plus actual shipping if you need.

    Waterproof Crimp Heat Shrink Connectors are a good way to make the splices. This is just one source. You may find better pricing if you search around.
    Waterproof Crimp Heat Shrink Connectors | Heat Shrink Connectors | Categories

    Get it scanned for codes.
    Clear the codes with a scan tool.
    Run it a bit to see which codes return.
    Jady1965 likes this.

  4. #3
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    So you don’t think that it’s the ECM? if so that is good new's, I’ll tack the harness that you have, how do we go about it.

  5. #4
    Moderate Moderator Steve in Chicago's Avatar
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    I don't know for sure if it's the ECM or not, but if your ignition harness is crumbling, you'll want to get that fixed either way.

    I'll PM you about the rest.

    If the car didn't misfire at all, then suddenly started misfiring immediately after the cam chain tensioner was replaced, I'd first look for a problem caused by that repair. Like I said, it's super common for the cams to go back in but be one tooth off time. Could also be old, cooked vacuum lines that decided to crumble and break open when they got moved around during the work. The old, cooked ignition harness may have crumbled being bent around during the work. Look for things that may have happened or are a result of the latest repair job.

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    This is what I’ve done so far:

    Check that the TDC on the Camshaft’s, Timing belt and crankshaft are correct, check that the harness from the firewall to the coils are not shorted out, check for continuity of the wires going from the ECM to the coil pack, check Vacuum hose for leak’s or disconnection of any hose, so far everything check OK, I had the battery power disconnected over night, reconnected the battery, I cleared the error codes for the ECM, and started the car, misfire continues, reed the ECM error codes and got this:

    P0300 Multiple misfire
    P0304 Cylinder 4 Misfire
    P0302 Cylinder 2 Misfire
    Last edited by Jady1965; 11-19-2012 at 02:53 PM.

  7. #6
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    Does the AUG use an ICM? If so, maybe the failed pack triggered a failure in that failure-prone part?

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    Moderate Moderator Steve in Chicago's Avatar
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    Nope. Only the silly old AEB.

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    How can i test the ecm to see if its working corect the cel flashes when it comes on

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    Moderate Moderator Steve in Chicago's Avatar
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    The CEL flashes when you power on the ignition? Or, the cell flashes as soon as the engine is running?

    If you've tested for the four coil trigger signals and they are present, that says the ECM is doing it's job as far as that part of the ignition goes.
    To test further than that, I imagine you may need to swap it out.

    How is the harness for the injectors? Try swapping injectors around?

    Double check the grounds to the coilpacks too. Pin 2 & pin 4 both need to see good ground. This side of the circuit is just as important as the power side.

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    The CEL flashes when I start the car, the ground the coil pack are well grounded I’ll check the injectors this afternoon.

  12. #11
    Moderate Moderator Steve in Chicago's Avatar
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    Have you done a compression test? If #4 is way lower then the others, that will tell you something.

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    I just did a vaccum test and acording to a vacume thred that I have fom this sit, i mite have a valve problem, i'll have a compresion test tool by tomorow

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    okay, cylinder 4 has 0 PSI compression, Cylinder 1,2,3 came up with 120PSI, I'm guessing that the 2 battom intak valves are bent, is that a good guess?

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    Moderate Moderator Steve in Chicago's Avatar
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    Did you move the crank during the cam chain work? Did you fasten the cams back down with the timing belt out of time? Either of those could cause valve/piston collision and bend some valves. You'll need to get the head repaired or replaced. Chances are you'll only need to replace a couple of valves. Don't run the engine till you get the head addressed. Worst case scenario is a bent valve breaking and dropping into the cylinder with a reciprocating piston.

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    I can't see anything inside of the cylinder cabity, but I'll be taking it apart today, I'll keap you posted

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    I've got the socket for the head bolts if you will be doing the work yourself. I am right by the hospital in Grapevine if you want to borrow it. Send me a PM or Email.

    Paul.

  18. #17
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    I'll now this afternoon if I have the socket or do I need to barow one, thank you.

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