OK, here's the deal. 1990 L98 133K miles

1st...I'm a licensed aircraft mechanic with about 20,000+ heavy maintenance hours on helicopters and fixed wing so I know my way around tools and stuff and I work on my car just like I would an aircraft, I have my tech manual open and I tag my parts...nuff said

I had a suspicion that the throttle body on my '90 L98 had never been cleaned and I was correct, it looked like it had bits of charcoal down its throat and when I removed it the backside looked like the darkside surface of the moon.

I cleaned the throttle body as described in "101 Projects for your Corvette 1984-1996" by using spray throttle body cleaner and a soft toothbrush and paintbrush...no scraping, scratching or anything like that. I also cleaned the ports on the plenum and they turned from dark brown/black to pretty aluminium.

I reinstalled with a new gasket of course (18 inlbs torque), hooked up the vacuum and water lines so on and so forth. Double and tripple checked connections.

The thing runs like a log wagon....Loping at idle and no power especially when trying to go into passing gear on the road...falls flat on its fanny...Oh yeah...fuel pressure 36-37 lbs at idle and open throttle.

Before I did this the thing would snap your neck going into passing gear and it was smooth at idle.:wtf:

Sounds like the throttle positioning sensor needs to be adjusted.

Here is a good link to a detailed step by step.

Good luck. BTW I had to put a new one on mine.

http://www.corvetteactioncenter.com/kb/questions/276/1985+-+1991%3A+Technical+Article%3A+How+to+Adjust+your+E arly+C4+TPS+and+Idle+Speed

TPS may not be adjustable on 1990 up models, look for sloted holes on the sensor.

TPS may not be adjustable on 1990 up models, look for sloted holes on the sensor.

I'm not sure. Article said it was for 85 to 91.:thumbsup3:

TPS may not be adjustable on 1990 up models, look for sloted holes on the sensor.

:thumbsup3:Correct...up to 1989 the setting was .54volts +/- .5 with MAF but with the 1990 Speed Density it is more or less fixed and the range is .36 to.96 Volts. I drilled the holes on my 1990 TPS bigger to have more adjustment but no change. The TPS on a 1990 runs from a precalibrated table in the computer.Hate my Speed Density for the fine tuning.