Pontiac Repair: engine sensor problem, electric cooling fan, pontiac grand prix

Question
hey, I have a pontiac grand prix 1990 3.1 multiport engine,the car will not stay started at first. I would have to pump peddle, then after a few minutes it will catch and run, but the idle go up and down,when its up I hit the gas then it goes down then it go's up.then if I turn ignition off it will not start again,unless I hold my foot on gas

Answer
Hi kirk:

has the battery dies recently on this car? if so the engine computer has lost the idle control memory. If not then there are a lot of other issues it could be from a bad ground for the engine control computer to a bad power feed to the computer. That perticular year car had ALOT of bad computer's!!! if you were to replace the computer the new one needs to learn the idle control as well. I'm not telling you to replace it but that was a really common issue with that car!!! the computer is on the right hand inner fender well remove the plastic cover and with the engine running use a screwdriver handle and tap on the computer a few times if it dies the computer is bad.this in a nut shell is how to re learn the idle either trying it before or after after replacing a computer. diconeect the battery and leave it disconnected for a few minutes. Clean the throttle body plat and bore to make sure it's free of carbon. reconnect the battery. turn the a/c off in the car. set the parking brake. start the car and put it in gear stay in the car just in case the parking brake doesn't hold. If the brake doesn hold just let the car run in park. if it hold let the car run for 10 minutes then shut the car off for 30 seconds and then start it up again and let it run for 5 more minutes or untill the electric cooling fan turns on from the engine getting hot. If the fan turns on your done then. If not let it run the full extra 5 minutes. That should do it for you. good luck :}