Misfire problem.
05-26-2006, 05:30 AM
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Misfire problem.
OK, here is one for you to test your automotive mechanic skills.
Car is hesitating (misfiring) pretty bad especially during warmer weather and when the engine warms up. The ECU registers Cyliner #4 misfire. All plugs and wires were replaced with new. Wire resistances and coil output resistances seems consistent between cylider pairs. As you know this system uses waste spark method meaning 3 coils. When VAGing the car during driving I recorded cyl #4 misfire and occasional misfire #5 (although very rare on 5).
Any other diagnostics that I can do before I attack the injector for #4 cylinder? If the coil was bad wouldn't I get misfire on a pair of cylinders due to the waste spark aggangements?
Any tips of the trade would be much appreciated. Any way to test injectors with VAG-COM?
Thanks as always.
Car is hesitating (misfiring) pretty bad especially during warmer weather and when the engine warms up. The ECU registers Cyliner #4 misfire. All plugs and wires were replaced with new. Wire resistances and coil output resistances seems consistent between cylider pairs. As you know this system uses waste spark method meaning 3 coils. When VAGing the car during driving I recorded cyl #4 misfire and occasional misfire #5 (although very rare on 5).
Any other diagnostics that I can do before I attack the injector for #4 cylinder? If the coil was bad wouldn't I get misfire on a pair of cylinders due to the waste spark aggangements?
Any tips of the trade would be much appreciated. Any way to test injectors with VAG-COM?
Thanks as always.
05-26-2006, 12:43 PM
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Check the wires that go from the power output stage (ignition amplifier) to the ignition coils
The wiring runs under the intake manifold (on my '96 A4).
I had this problem, so maybe you have the same issue: Eventually the wire insulation rubbed through, causing misfire like you described. This happened especially in wet weather. Ultimately, a few miles later, one of the dual coils shorted out. Although the time from the first symptom to coil failure was very short, the insulation, judging by the amount of deterioration and corrosion of bare wire, must have been compromised for at least thousands of miles.
Of course, it could be just a bad spark plug.
I had this problem, so maybe you have the same issue: Eventually the wire insulation rubbed through, causing misfire like you described. This happened especially in wet weather. Ultimately, a few miles later, one of the dual coils shorted out. Although the time from the first symptom to coil failure was very short, the insulation, judging by the amount of deterioration and corrosion of bare wire, must have been compromised for at least thousands of miles.
Of course, it could be just a bad spark plug.
05-27-2006, 05:44 PM
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Re: Misfire problem.
maybe we can combine some knowledge here. i got a 96 cabriolet 12v v6 with engine light on due to misfires. came in with faults stored for #4 and #6 although #6 seems to be the one that keeps returning. it has rough idle. new wires, swapped plugs which are also pretty new, i also checked the egr and thats working good. i unplugged the idle stabilizer and the idle did not change so that was gonna be my next step.(remove and clean) i know its working electrically(output diag with vag-com) i was also thinking of swapping injectors. I thought there was a recall on the fuel rails on those 12v engines but it didnt apply to mine so no luck there but maybe you should check that
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