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vwnewton, VW Owner,ASE Master and L1 Advanced
Category: VW
Satisfied Customers: 660
Experience:  25 years of VW obsession turned into a job, last 15 years as a VW Tech.
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2005 VW Passat: cylinder..light keeps coming..of the ignition coils

Customer Question

I have a 2005 VW Passat 1.8l 4 cylinder and my chec engine light keeps coming on. It continues to show miss fires in various cyclinders and have changed all of the ignition coils. please adsive what the probem could be. Plus the car is running really hard
Submitted: 8 years ago.
Category: VW
Expert:  vwnewton replied 8 years ago.

Hello, Jason here to help. If the misfire doesnt seem to stay with a cylinder, and a P0300,301,302,303,304 is generated, then there are other causes. A coil when it fails will cause a single cylinder to misfire.

Mass Air Flow Sensors(MAF) do fail quite often and will cause multiple random misfires.

A clogging fuel filter will also cause the same codes.

The fuel filter is often overlooked, and is inexpensive. If you have over 50k miles, change the filter first.

If there was also a P0171(system lean) code then this is a very likely cause.

If the MAF readings are low, either a dirty or failing MAF is likely. The MAF can be cleaned with MAF cleaner, Also inexpensive.

Another possible cause is a vacuum leak between the airfilter/MAF housing and the throttle body, or under the intake manifold. Usually will have a sucking/whistle noise at idle in that area if that is the cause.

A parts store can scan the car for free usually, record any codes and let me know.



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Expert:  vwnewton replied 8 years ago.

Please let me know if more information is needed before leaving feedback.

I want you to be happy with my answer!

If the fuel filter isnt the cure, or if no vacuum leaks can be heard or seen, please reply.

Testing the MAF sensor after cleaning will require a scantool if no codes like P0171,P1136(lean fuel mixture codes) are present.