Help with misfiring on certian cylinders

[midnyite]

What does it mean when only certain cylinders misfire. And it seems it only happens when i am in boost. Dont remember the exact cylinders but something like 1 , 3, 6.

Also i am tryin got find a boost leak or problem somewhere with my turbos whining like shit. Sometimes i cant hold boost, sometimes i can. There are times when it overboosts to 25PSi and then it goes back to normal where it boosts 21-22. Then it wont go past 17-18 sometimes. This shit is wierd cant figure it out. Had the shop smoke test it and they say there are no leaks. Does this sound like N75 failure or DV? DV were brand new from about 8 months ago.

Thanks

[midnyite]

Also what is the vacuam supposed to be at when sittiing still?

[BITRBO]

If the misfires keep coming back to the same bank of cylinders, it's likely that the ICM is bad for that side. If you have the time/patience, you can swap the coil packs just to be sure. That might be related to your boost issues, but you might just wanna log blocks 115 just to see what's going on.

edit: vacuum should sit around ~20inHG, or ~17inHG with the a/c on.

[JD797]

what do you mean by whining? Like dentist drill? Cuz the turbos themselves could be bad. Also, have you checked spark plugs for misfiring?

[drkenan]

Your valve cover gaskets could also be leaking and causing certain cylinders to misfire. I have that problem right now but haven't had time to fix it. Actually mine is very similar to what your are describing except that I never actually overboost. Maybe check that as a last resort?

[cmagalis]

Well it could be one, or many problems. For the miss fire it could be a bad coil pack. As for the boost problem, the turbos should be fine. If there isn't blue smoke pouring out the back your ok. When you run 20+ psi of boost your looking at a ton of new issues anyway. The turbos will make some noise because they are compressing air and have an inlet. To me it sounds like theres a bad sensor or valve somewhere in the car. My recommendation for you is to find someone with a VAG scan tool and have them do an engine log.

[Rajan147]

how many misfires/ cylinders, which cylinders and does it throw a code or CEL?

[cmagalis]

Also a very good thing to check too

[1997gtx]

The boost issues sound like a bad N75, but with the misfirings, your problems could be deeper. Have you installed new plugs recently? Have you scanned the car?
--Adam

[midnyite]

Only misfires when i am in boost, IIRC it is 1 , 3 ,6

how many misfires/ cylinders, which cylinders and does it throw a code or CEL?

[midnyite]

What is a ICM?

If the misfires keep coming back to the same bank of cylinders, it's likely that the ICM is bad for that side. If you have the time/patience, you can swap the coil packs just to be sure. That might be related to your boost issues, but you might just wanna log blocks 115 just to see what's going on.

edit: vacuum should sit around ~20inHG, or ~17inHG with the a/c on.

[midnyite]

So this is what i have gotten so far.

Boost leak can be a N75 or DV, or maybe even a leak from the inte3rcooler or hose?
Turbos did not whine before the installation of the intercoolers. This is like major whining at boost, not your regular startup. Also is coming only fromt he right side.
ALso the DV's are only 8 months old, hyper boost DV's do they actually go bad?

As for the misfiring, Coilpack? Plugs? just had them installed about 1500 miles ago. Bosch Platim plugs.

Vaged the car last night and only got the misfire and something with my o2 sensor. But i have been having tha for a long time since i am running test pipes.

Will get some logs tonight. First what blocks to log and second can someone help me graph the data?

Thanks

[1997gtx]

ICM = Ignition Control Module

[midnyite]

???

[midnyite]

Just checked the misfires and they are cylinders 1,2,3
Also did some logs, anyone here can help me put that in graphing and tell me whta swrong with the car?

Thanks

[volks88]

Just checked the misfires and they are cylinders 1,2,3
Also did some logs, anyone here can help me put that in graphing and tell me whta swrong with the car?

Thanks

swap the ICM's (top of the airbox) then vag the car again. if it jumps to the other side, well then thats it

[midnyite]

Dam, thats a good idea. Thanks!! Will definetly try that.
anyone else can help with my logs?

[cmagalis]

Honestly it may be worth taking the car in so you don't end up spending money on un-necessary parts. It's a lot easier for a trained pro to give you the right info. Then fix what he tells you! It's not a bad thing!

[cmagalis]

As for the o2 sensor bugging out its probably one of the probes in down pipes. There are few aftermarket down pipes that dont throw faults for cat efficiency. Most of the aftermarket dps' run fewer cell count units than the factory Leistritz cats to give less restriction.

[AudiSportB5S4]

Only misfires when i am in boost, IIRC it is 1 , 3 ,6

when you misfire in boost, thats usually a GAPPING issue on the plug. what plugs did you install?? try re gapping the plugs OR try the Bosch F5DPOR Plugs everyone talks about. I have them in my car and runs great. they come pregapped you dont touch em!

[midnyite]

Thats what i am using now. the plugs are only about 1500 miles old. So it should nto be the plugs.

[Boosted-S4]

It could be a tonof things!!! having bad o2 sensors will make ur car misfire bad too!!!!