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Discussion Starter #1 (Edited)
Vehicle: 98 Passat 1.8t AEB

I've been having Exhaust popping at idle, or another (or possibly better way of explaining it) Is like it's small weak combustions or misfired which makes the RPM's fluctuate within a 100rpm range at idle. For the past few weeks at idle when i first start up both cold and warm starts mostly when it happened. Idle will sit at ~875RPMs and the engine/exhaust will pop/misfire rather frequently.

I'm wondering if I'm running too rich somehow. Possibly oxygen sensor (my ECU tune doesn't have deleted 02).

My computer crash last week and I just repaired it myself and need to reload VCDS. What can I look for or monitor on VCDS??

Also not sure if its related but when I take off in first its like my car is struggling but when it does it takes off quick as usual...hmmm

Its not something that is really bad but whenever something happens with my car I like to catch it as soon as possible, like a hypochondriac for my cars!

Any other ideas welcome...

(FYI: I dis the R8/2.0 coil conversion so no crappy ignition coils or ICM's to deal with)

Thanks.
 

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I would first suspect having a vacuum leak somewhere in the PCV system. Having a check of the PCV system should yield some information on that. Check all hoses that are related to vacuum, they're aren't that many of them so it should be relatively easy.
Then I would try and get that VCDS hooked up and just do a scan and see what it comes up with.
Post codes and take it from there.
 

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PCV (aka bleeder valve) under the intake or a stuck open N80 purge valve on the airbox. Plug the line from the purge valve to the intake and see if the idle evens out and stops puttering.
 

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Discussion Starter #5 (Edited)
PCV (aka bleeder valve) under the intake or a stuck open N80 purge valve on the airbox. Plug the line from the purge valve to the intake and see if the idle evens out and stops puttering.
Thanks for the tip. I replaced the breather tube and surrounding bits like the bleeder valve last month but I will check out the purge valve didnt even think about it as I was looking for vacuum leaks.

Yesterday though I was driving down the freeway and I was only getting 10 pounds of boost instead of 15, and a loud whooshing sound when hitting boost. As soon as I tried to stop the brakes were stiff so I had an idea before I lifted the hood that something was up with the vacuum to the booster and low and behold the L shaped hose to the intake mani had popped off.

I'm wondeing if that booster hose popping off is related to my initial problem. Like if the bleeder pcv valve I installed was a dud and the crankcase pressure is off. Just spitballing ideas.
 

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Well, the L-hose does not connect to the crankcase directly, so probably not. The L-hose sees all the boost since it is directly connected to the intake manifold. When the bleeder valve under the intake goes, it usually blows through causing a vac leak AND can cause pressure build up in the crankcase. Although, the puck valve at the turbo inlet pipe usually takes care of excess pressure..

You've got two things to try, then. First block off the line to the N80. If that doesn't work, pinch the bleeder valve hose shut and try it out. Do them separately or you won't know which one may have fixed the problem.
 
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