P0302 Misfire at Idle, ideas?

[1RMDave]

Hi, I just picked up a 2011 GTI 6MT on Saturday, I got a good deal on it but it has a CEL that flashes at idle and then stays on solid. It it always cylinder 2 misfire. It has a few mods (3" exhaust/dp with no cat, injen intake and APR stage 1). Here is what I have done so far:

- Replaced intake manifold
- Cleaned intake ports/valves with walnut blast
- Replaced PCV valve
- Replaced coils and spark plugs
- Checked compression (140 psi in cyl #2), little low but ok
- Checked for vacuum leaks using brake clean.

When I am giving it gas and driving it feels find, but at idle it always has a miss, you can feel it and it immediately sets a code for the misfire. I am starting to think a possible faulty injector causing a lean condition in #2 at idle. Any body have something similar happen or have any ideas? I might swap the injector to another cylinder today, I just don't want to keep pulling the intake manifold off.

 

[mto386]

I've had misfire CELs that have lead to 3 out of 4 injectors replaced under warranty.

 

[johnboyGTI]

Sorry I don't have an answer on your misfires, but I'm not sure that you should use brake cleaner to check for vacuum leaks. You should use carb cleaner, or better off, use a fog machine. Brake cleaner is very harsh, and could damage sensitive items that might get incidentally sprayed.

 

[1RMDave]

Fog machine would be sweet.

I moved the injector to #4 today, nothing changed. Any chance it is the 3" catless dp and exhaust? Would a stage 2 tune help?

 

[1RMDave]

Possible vacuum leak at the vacuum line running over the valve cover from the n80 valve to the turbo. Does anyone know what this line is called or what it's purpose is? It has a check valve in it at at the rear of the valve cover (left side, facing engine)

 

[JerZ_MKVI]

Hey guys new to the forum btw ! But you said compression at cylinder 2 was a bit low compared to others. So id say recheck you intake valve on #2 to make sure while cleaning you didnt get some carbon stuck thats wedged in between causing lower compression and a miss.


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[JerZ_MKVI]

Also not sure about what vacuum line you're talking about but if that was the case would't it cause more than just a single cylinder missfire?


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[1RMDave]

I did a leak down test which i would think would show a valve not seating correctly. It did not end up being that vacuum line (the line goes right under #2 runner). As of now i still have not resolved it. Going to swap injectors and inspect valves again tonight.

 

[JerZ_MKVI]

Ok good luck on it ! But remember to go back to the basics air, spark, fuel, and conpression. I see you also replaced coils and plugs. I've seen many faulty brand new. Check for spark of the coil and proper gap for the plug.


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[1RMDave]

I bought aftermarket coils, maybe I will try a set of R8 coils...

Anyone think 150 psi compression might cause a misfire at idle?

 

[FriggenT1]

Re-gap the plugs? New or old plugs? Have you reset the code yet to see if it comes back?

 

[1RMDave]

Brand new NGK iridium at whatever gap they come set at. If plug gap was no good I would think there would be misfire when boosting. I've reset the code 50+ times it comes back within 2 minutes of idling, every time.

 

[JerZ_MKVI]

Take the coil and plug out and check for spark on #2 or get a or rent a coil spark tester. Because i havent heard anything good about aftermarket coils. Or clear codes take coil #2 and swap with another cylinder and see if it moves, if it does then you have a faulty coil


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[1RMDave]

I did the coil swap but it did not change anything. However it's bastardized mix of 2 old oem coils and 2 shitty aftermarket coils. Today I ordered new oem r8 coils. Problem is that it isn't a dead mis. I will still see spark at idle, I'm just wondering if it is inconsistent spark.

 

[JerZ_MKVI]

Oh missed the only at idle part lol but did you try swapping the oem with the aftermarket?


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