Ideals for my "routine" misfire after long trips?

[vwGLI]

Hi all,

I had my check engine light on for 3 times in the last few months. It always says Misfire on Cylinder #4. It always happens on the day right after a road trip, about 300 miles freeway driving. The light always goes off by itself a few days after coming home. Strangely, with the CEL on, there was nothing actually feels like misfiring. The engine starts good, idles smooth, pulls good, fuel consumes normal.

The only thing I can put together with the issue was bad gas. But i doubt i am that lucky enough to have bad gas on every trip. Another consideration, I've heard the heat soak issue causing misfire on Jeep. Is that the reason here? This is really annoying~ need advice from you guys. Thanks in advance!

My car is a 2.0 tfsi VW Jetta GLI with 71K miles. It's in good condition except the engine burns a bit oil (which i believed is "normal" for vw&audi).

 

[spasm3]

Has it been serviced i.e. plugs pcv ?

 

[Warstud]

I was thinking a bad plug running hot.

 

[The Critic]

Have you checked the fuel trims or tested the coil packs?

 

[vwGLI]

Originally Posted By: Warstud
I was thinking a bad plug running hot.

forgot to say~ coils and spark plugs were replaced in the last year. The misfire reminds

 

[vwGLI]

Originally Posted By: spasm3
Has it been serviced i.e. plugs pcv ?

plugs are new but not pcv

 

[JimPghPA]

71K is the kind of millage where a dirty fuel system will causes problems.

How old is the fuel filter? Replace the fuel filter if it has more than 30K miles on it. While you are at it check the air filter, and replace it if very dirty.

Does it have a fuel metering system that individuality controls the fuel for each cylinder. If so, put a bottle of Techron "fuel system cleaner" (NOT THE FUEL INJECTOR CLEANER) in a tank of gas and run that tank until it is very low, like 1/8 or less of a tank left.


If this cures the problem, you might want to repeat the Techron every once in a while to keep the fuel system clean.

 

[rjundi]

A friend with Fahrenheit edition suffered the same thing. Turned out to be I think valves and required changing the springs out if I recall correctly. Definitely work in the head. Best of luck.....

I love those cars, but again they deliver on the nutty problems. My first car was a 1988 VW Gli 16v and I loved it except for all the electrical problems.

 

[PandaBear]

When I had bad gas in the past it is always the first thing in the morning when I start the car cold, with multiple cylinder misfire CEL or a stumble that goes away after a few cranks. Water condense at the bottom of the tank.

I'd expect fuel filter problem to affect all cylinder equally instead of just 1 cylinder. So it must be something that is unique to that cylinder, like plug, wire, coil, injector, and as rjundi said possibly valve or even intake/exhaust manifold.