intermittent limp mode

[slapshotjh]

Car is a 97B4V. It has started going into limp mode. Some days it limps frequently, other days you can't get it to limp even on the longest hills. I've driven an A# with a stuck wastegate, and was able to feather in and out of the throttle to keep it from dropping into limp mode (not keeping sustained overboost). This car will drop into limp mode quickly when it happens, very little time on the boost before it limps. Feathering throttle to alter boost pressure won't trick the ECU into staying out of limp mode.

I figure its an electrical issue, or the N75 is on the fritz. The N75 was new 2 years ago maybe 20,000 miles on it. All the pressure lines have been replaced per the FAQ (yes in the ECU as well). I wouldn't think the wastegate would stick intermittently, and I would not think that a pressure loss in a leaking hose would only happen from time to time.

Has anybody had a flaky limp mode issue like this? Anything I should look for?

 

[JASONP]

from what I recall, these cars have a vac hose going to the ECU that tends to crack overtime,maybe worth a looksee

 

[sfierz]

How about MAF or intake manifold? If the intake is clogged you will get very little power. Is the boost line to the turbo OK? If the MAF connector is dirty you can get poor readings. Also, double check new lines to N75. They could be reversed, causing this condition.

 

[87turboquattro]

i'd look for air leaks.if your over boosting,look at the intercooler.i found mine was leaking,only because i was upgrading to a eurojet and 2.5" piping.

 

[slapshotjh]

Thanks for the help guys. This is an intermittent problem. SOme days I can keep the accelerator to the floor all the way up long hills on the highway. So I don't think its a leak. And yes, as I stated the hose in the ECu has been changed. Some days it drops into limp mode on flats with only a little accelerotor pedal effort. Other days you can't get it to drop into limp mode.

The car is not low on power, the intake was removed and thoroughly cleaned about 15,000 miles ago.

 

[rdkern]

This is an intermittent problem.

These types often are electrical. If I had this issue, I'd be certain that the connections to N75 and maf are good.

Is there any relationship to the weather conditions?

 

[slapshotjh]

rdkern, I think you may be right. I read your post and fiddled with the connections on the N75 and the MAF. took them off, and put them back on - wiggled the wiring harness near them. On the 10 mile trip from work to day care the car ran great. Could not get limp mode. On the way back it dropped into limp mode.

This car was converted from a VR6 by myself. The wiring harness was a mess, with several shorted wires that needed to be repaired before the car would run. I think I need to take a look at the harness again.

 

[rdkern]

irregular issues are tough, since you really never know if you've fixed it.

Good luck with this.