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mike2765
mike2765, VW Technician
Category: VW
Satisfied Customers: 308
Experience:  Certified VW technician with 10 years of dealership experience
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I have had the check engine light on short while now and the

Customer Question

I have had the check engine light on for a short while now and the trouble code has been a random misfire and misfires on#1 and#2. The other nght coming home the engine light started flashing and the PCM light came on. I lost power and limped the car the final stretch home.
After geting home the car died and wouldn't restart. Codes P2293 and P0300 were on my scanner. After some troubleshooting and online research I went to the dealership and purchased a new High Press Fuel Pump and Fuel Press Sensor.
After replacing these parts the engine ran again but gave me P0300, P0301 and P0302 for random misfire and misfires on #1,2. A lot of white smoke in the exhaust and actually smelled like raw fuel.
I changed the plugs, swapped the coil packs, checked the intake for vacuum leaks and nothing that pointed to anything obvious.
As a side note I have two things. Several months ago I had my car to VW for service and they complied with the mandatory service bulletin to replace the intake manifold but informed me after the car was back together there was a substantial build up of carbon on the valves. Also the other day was the first time I've used 93 octane I have been using 87 since I bought the car.
I don't know if there is something more substantial going on or if I was to pull the head to clean the valves...
Submitted: 1 year ago.
Category: VW
Expert:  mike2765 replied 1 year ago.

Hello I'm Mike. The direct injection system on these engines causes build up on the intake valves. It is very common. To fix this. You just need to remove the intake manifold. And clean the intake valves. Just have to scrap the the build up off the valves and around the valve seats using a pick set or if you have a walnut blaster that's the easiest way.

Customer: replied 1 year ago.
How does build up on the intake valves explain the misfire, white smoke exhaust and raw gas coming out the exhaust pipe ?
I'll almost try anything but want to make sure it's logical.
Expert:  mike2765 replied 1 year ago.

Because of injectors are directly in the combustion chamber there is no way for the fuel to clean the back of the intake valves so it build up with carbon and oil coking. So when the engine is cold started the carbon is hard which causes the valves not to seal which makes the engine misfire when cold started.

Expert:  mike2765 replied 1 year ago.

This is a major problem for all manufacturers that use direct injection.

Expert:  mike2765 replied 1 year ago.

When I replace intake manifolds under warranty I usually offer to clean the intake valves since the manifold is already so it saves the customer some money.

Expert:  mike2765 replied 1 year ago.

please don't forget to complete the rating/accept my answer thank you

Expert:  mike2765 replied 1 year ago.

any more questions/concerns. a positive rating would be appreciated