GTB revs sticking at 1800-1900rpm

[Guest]

Been having an issue with my 98 GTB (auto). From cold the revs tend to stick at about 1800-1900rpm for 2-3 seconds and then they will suddenly climb to 2400-2500. Happens under light or heavy acceleration but doesn't happen every time I go through the 1800-2000rpm mark. I can hear a whine from the turbo as though its spooling up but I get no power from the engine.

When the car warms up it's a bit better and happens less frequently but still occurs. Occasionally when driving at constant or gentle acceleration the power will 'fluctuate' with it disappearing and then reappearing (sometimes several times) until I get off the gas completely and then ease it back on.

Getting to the point where I can't trust it to have consistant power through an intersection and have been left hanging for precious seconds a few times now. Have had it into Winger they did following:

Removed and cleaned AFM

Upper engine clean

Renewed air filter

Checked for air leaks

Removed intercooler and tested vacuum diaphragm

No improvement in vehicle behaviour.

Could this be a fuel injection issue? Thought I'd get some opinions before I go and pour more $$ into a fruitless search.

NB: have had an idle issue previously and got the idle speed control cleaned and idle speed adjusted. Was dropping idle revs in drive from about 800 to 400rpm, been pretty good since adjustment but has just started occasionally doing it again (always catches it and brings it back up to 900-800rpm tho). Not sure if this is in any way related to above issue.

[log1call]

Have you had the throttle position indicator checked?

Have you tried a standard tune up and a fuel filter change?

Both pretty standard first steps.

I assume wingers would have checked for trouble codes and asked you about it's service history?

[Guest boostin]

 log1call said:

I assume wingers would have checked for trouble codes and asked you about it's service history?

Haha, good one!! ;D

[thorpy]

Our 2000 GTB is doing EXACTLY the same thing , have spent $450 so far trying to find it , runs fine for the mechanics and no codes , fault is very intermitent.

[thorpy]

Have had a thought on this , any ECU gurus out there maybe able to help.

The other day I reset the ECU and then went for a drive and found the problem was really bad.

So I was thinking if the problem occours when engine is cold and also when ecu is reset , then the car would be running on the preloaded maps in these states and if a map was corrupt then this could be the cause?

Correct me if im wrong , just assuming things from my limited knowledge.

[Guest the_return_of_the_jedi]

another reason we dont like twin turbos sorry guys

[Guest]

This is probably a bit of a stretch... is the aircon on? Cos the revs will drop when the compressor kicks in and maybe it isn't compensating properly?

[thorpy]

Nope aircon not on.