help needed with 02 C4S - Misfire # 6

[CAS-4S]

SO, I got a beautiful CEL on my 02 C4S coupe 6 speed with 63k miles on it. After diag, the shop found a misfire coming from 3 cylinders (#4,5,6). The initial recommendation was to change the coils and plugs. So I changed all the coils and plugs on both sides. After completion, the misfire was still occurring with a heavy rough idle, this time, specific to cylinder 6 only. Then, i changed the injector for cylinder 6 (shop recommendation). After the injector, the rough idle was still present with the engine light as well. Then, the shop performed a leakdown test and found gas in cylinder 6. They cleaned it up, swapped coils from 5 and 6 to test proper functionality of coils. The leakdown test did not show any leaks however. SO after this was all said and done, the shop put it in additive, filled up the gas tank, and drove it for 50+ miles or so. The car function properly according to them and I drove it as well, and there no idle, no shaking, no engine lights, nothing. A week after I picked up the car from the shop, the rough idle began again after I gave the engine a little rev. The engine light was flashing, and the rough idle began again. The shop said it could be the lifters for cylinder 6. 

 

Any thoughts or anyone here experience similar issues with this? Any help would be greatly appreciated. I would like to gain some knowledge before taking it in back to them and throwing more money at this with no end solution.

[Bilal.utah]

I had the same problem with my 911, it only used to missfire if i go over 5000rpm if i keep it under then i have no problems at all, i did some research, i changed plugs and coils etc then found out it could be lifters, i changed those and the problem is gone but get more info from other people before you do those because lifters are pricey


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[CAS-4S]

Bilal thanks for the response, did you change all the lifters for every cylinder or just the cylinder that you had a problem with?

[Bilal.utah]

I changed all cylinders because i didnt want the others to fail and we have to get back into the engine to replace them


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[Bilal.utah]

I only had a misfire when i was above 5000rpm anything under that would be fine


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[Schnell Gelb]

You need a complete diagnosis with Durametric or PIWIS. Until you have all that data ,it is just hit/miss/speculation. That said, neither diagnostic will identify specifically worn lifters. Worn/filing lifters is usually identified by ticking hot+cold with an electronic stethoscope.

[CAS-4S]

Just to update and close this thread. I ultimately replaced the lifter for JUST Cylinder 6, and that fixed the issue. Never had any more rough idle or CEL lights.