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vwnewton
vwnewton, VW Owner,ASE Master and L1 Advanced
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Experience:  25 years of VW obsession turned into a job, last 15 years as a VW Tech.
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VW Passat 2.0T: misfire..cylinder..4 new coils, cleaned intake, ran

Customer Question

VW Passat 2.0T P0304 DTC misfire on cylinder 4 upon cold start. Installed 4 new coils, cleaned intake, ran injector cleaner, problem persists. How do I fix the problem?
Submitted: 4 years ago.
Category: VW
Expert:  vwtech0405 replied 4 years ago.
Welcome to just answer!!!


Have you checked the condition of the spark plugs?
Customer: replied 4 years ago.

Spark plugs were replaced 30,000 miles ago; there is no missing after initial cold start and warm-up period of about 20-30 seconds. Once the car idles down the engine vibration disappears and the engine runs smoothly, accelerates fine and the check engine light does not come back on if reset after initial cold start. All 4 coils were replaced by VW under recall so they are brand new.

 

I have researched and am wondering if the MAF sensor could be the problem.

Expert:  vwtech0405 replied 4 years ago.
We have not seen many issues on the mass air flow meter on these model car . What you can try is swap the plug over to another cylinder erase the fault and see if the misfire follows the plug we have had a couple of issues with the plugs in these vehicles especially if they are not factory.
Customer: replied 4 years ago.

Plugs are factory and were installed at the VW dealership. I don't think it is the plug or it would run rough even when engine warmed up.

 

If not the coil and not the plug causing the misfire on cylinder 4 when cold start, then what else upstream can be checked? Is there a fuel temperature sensor on the engine that might be bad?

Expert:  vwtech0405 replied 4 years ago.
There are 2 fuel sensors in the system one under the intake and another one on the side of the high pressure pump the one on the pump is for checking pressure wich we have seen many issues with. Can you read fuel trim values with your scan tool if you do what are they??
Customer: replied 4 years ago.

No, I cannot read fuel trim values with my Diag tool. High pressure fuel pump was replaced 3-4 months ago by VW so that is probably not the problem.

 

The car idles roughly for the first 30 seconds during cold start only. After the engine idles down, the check engine light comes on with the P0304 code engine misfire. This message is always related to cylinder 4. What could cause this if spark plug and coil are good on cylinder 4? Is there an ICM (Ignition control module) on this engine? They had problems with the ICM on the 1.8T engine.

Expert:  vwtech0405 replied 4 years ago.
they had problem in the early models but these models don't have a ICM . Have you checked compression in this cylinder ?
Customer: replied 4 years ago.
No.
Expert:  vwtech0405 replied 4 years ago.
If the plugs and coil has been check next step is to check compression

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