I just replaced my automatic in my 89 350/auto formula with a six speed from a 96 z28. When i did this, I took out the hypertech chip for the 89 formula and put one in from a 89 vette with the maual. Now i am having serious idle problems when cold. It is as if the computer thinks the engine is warm. It turns the fans on at start up and runs like crap. Im pretty sure it isnt going into cold enrichment. Another problem is that when it is hot, the idle gets stuck way high unless i rev the motor, then it drops and surges for looking for 800rpm. Any help or suggestions would be appreciated, thanks

 

What kind of Thermostat do you have?
Have you tuned the chip at all?
Does the car get up to operation temperature and work fine or "good enough"?

Brendan

 

180 degree, havent tuned the chip, but have the capabilities to do so. The car runs fine once it warms up somewhere around 140 degrees. With the automatic chip, the fans only turned on around 180, maybe i damaged the temp circuit during the tranny swap, i did have the dash out??? Thanks for the replies...much appreciated