2001.5 S4 6spd, stock other then K04 upgrade on stock program and AWE boost gauge. I noticed every once in a while I'm only reaching about 6 PSI of boost. Seems to happen once the car warms up a bit but not always. When the oil temp isn't quite up there yet (but slightly above 150) and I give it some gas to see the boost, it'll peak higher then half a year ago when I put the gauge in. About 10 PSI instead of 8-9. But then a few min later when the car warms all the way up it'll cut back down to 5-6 psi.

Does anyone have any thoughts on what the problem could be? Only work I did to the car recently was remove and grease the wiper assembly (slow wipers suck!) but I think the problem started before that. Car has been running on K04s with stock program for over a year now (saving up for Stage 3-) No CEL either (though it was pulling a warm up catalyst code but randomly goes away and I haven't seen it in a few months.)

 

sounds like your getting limp mode. You should scan for codes with vcds. running k04's on stock programming will cause a lean condition. Also boost changes with temperature. the hotter it gets the more boost the stock ecu requests, to make up for less dense air.

You got PM.

 

Checked the codes today after it warmed up again. Same warmup catalyst insufficient code as well as both EGT sensors short to ground. One of the EGT sensors was replaced 6 months to a year ago. Would the lean condition wear out sensors that fast?

I can only tell myself "duh" about the extra boost, thermodynamics were my best classes in college so far...

I'll consider your tuning service once I finish my engine swap into my Fiero, the pricing is a heck of a lot less then giac.

 

i'm in the same boat as you right now with k04's and no tune at the moment. i have never had my car go into limp mode due to it though. Are you sure you dont have a torn boost hose somewhere. i also get the catalyst code and it does go away sometimes. jude is probably right but i'd check for leak to be sure.

also **** those egt's! i'm coding mine out along with the rear o2's the second i get a tune.

 

Well I got that intake pressure tester from AWE and found a blown off hose clamp on the driver's side turbo inlet (034 Motorsports K04 inlets) so got a new clamp tightened down. Pressure tested again and everything seems all right. Disconnected the battery when I got home to reset the computer but to no avail. I'm still having the same problem.

It's starting to seem random when it'll cut back the boost. The other day I was driving the 30 miles to school, a quarter of the way there checked to see how much boost I was getting and it was stuck at 6-7. Then about half way there I noticed I was getting full boost so gunned it. 1st, 2nd full boost all the way though the gears but once I hit 3rd, it cut the boost at about 4000 rpms at full throttle. Could this mean there is an overboost problem? Could one of the vacuum lines running to the waste gates have come lose or gotten a hole?

Most of the time I drive very light, not going much past 2000 rpms before shifts so there is never time to build max boost.

Can anyone think of anything else to check? Still no Check Engine Light and I cleared the codes the last time I looked to see if anything comes back.

 

replace all the vacuum lines and check the n75 valve.