Idle problem

I have an 87 GN with an idle problem. First off my car is almost all stock, with only 50K miles. The car drives perfectly fine, and idles perfectly fine while in drive. Its only at park when it doesnt idle right, and it is intermittent. In drive, it idles at around 700 rpms. In park, it will idle at 100-700rpms-up and down randomly and eventually cut off-sometimes. But it only does it randomly. Sometimes it will go up and down, but not shut off, but hesitate like it wants to shut off. I thought it was the TPS sensor, so I changed that out. It helped, but now I have another problem. My idle while driving is now around 800 rpms, which I think is good. While it is in park it now idles around 900-1000rpms, which seems good. The idle doesnt go up and down from 100-700rpms anymore. My problem now, is when I start the car in the mornings, the rpms shoots to 1500-1600 rpms and stays there, and the motor seems to get real hot if I leave it for about 5 minutes. If I shut the car off, and start it again, it will go right to 900-1000rpms again. That is the only problem now. What do you guys think?
 
Check for vacuum leaks. Have you checked/reset the IAC? What chip are you running?
checked and no vacuum leaks. Have not reset the IAC. How do you reset the IAC? Where does it need to be set at? I dont know what chip is in it. Supposedly all stock. I have only had the car for about a month. thanks....anyone else?
 
As was said above, did you reset the iac after you put on your new tps? You could also try spraying out yout iac and throttlebody.Tuning. Any stock car can also use a scanmaster, if you ask a problem most will wanna know your scanmaster readings to help diagnose your problem.
 
No I do not have a scanmaster. My car is almost all stock, and I was told a scanmaster is not too necessary for a stock car.

Whoever told you that gave you bad advise. Some type of scan tool is absolutely necessary to tune one of these cars correctly. With todays gasoline the stock chip is outdated. There are very good aftermarket chips out there like TT that will greatly improve the overall performance of the car. You need a scan tool so you can see exactly what the computer is seeing so you can set the car up properly.
 
Your current situation is pretty straight forward spelling out the need for one. Since the early days on these cars a scantool has been a must.
Any research will show that. Not trying to shove sarcasm down your throat but the scanmaster at a minimium is a great tool.

Fullthrottlespeed for the scanmaster

buickgn for the sun hood if you are inclined to bling it at all

its small and fits in the palm of your hand.
 
Thanks guys for the help. I will definately get a scanmaster. I tried following the procedures for the TPS, and it made things worse. Now the car dies while at idle in drive, and idles fine while in park. The complete opposite. I am going to try to reset the IAC tomorrow. Has anyone done this without burning up the computer? What should the idle be in drive, and in park?

thanks again!!!!
 
TPS can be set with key on / engine off & car in park. What was the idle TPS voltage you ended up with?
 
Whoever told you that gave you bad advise. Some type of scan tool is absolutely necessary to tune one of these cars correctly. With todays gasoline the stock chip is outdated. There are very good aftermarket chips out there like TT that will greatly improve the overall performance of the car. You need a scan tool so you can see exactly what the computer is seeing so you can set the car up properly.

I concur. Stock or modded, a Scanmaster is probably one of the best things you can do for your car. Along with a TT chip as mentioned. That scan tool can tell you all sorts of things on your engine you should know.
 
Something is going on with the IAC, the computer will open it when you turn the key on and then slowly close it once the car is running, it might be stuck or something.
 
I took the car to the mechanic, and had them adjust everything for me. They reset the IAC. Put a new IAC motor in(old one had a bunch of carbon in it), and adjusted the TPS sensor. They set it at .40. The car now idles at about 1200rpms for the first 15 secs. then drops to about 800-900rpms in park. In drive it idles around 600-700rpms. Is this normal? It seems a little low. The rpms dont move up and down randomly anymore. Does anyone know if all these numbers seem correct?
 
I took the car to the mechanic, and had them adjust everything for me. They reset the IAC. Put a new IAC motor in(old one had a bunch of carbon in it), and adjusted the TPS sensor. They set it at .40. The car now idles at about 1200rpms for the first 15 secs. then drops to about 800-900rpms in park. In drive it idles around 600-700rpms. Is this normal? It seems a little low. The rpms dont move up and down randomly anymore. Does anyone know if all these numbers seem correct?
Spent more time driving the car today, and got some more accurate numbers. When I first start up the car it idles at 1200rpms for about 15-20 seconds, then slowly drops down to about 800rmps, and will go as low as 700-750rpms at idle in park. When I am in drive it will idle around 550-600rpms. This seems really low both in park and in drive. Does anyone know where it should be at?
 
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