Low idle problem

Hi! I have a 1991 Buick Park Avenue w/ 157000 miles. I have the 3800 V6 w/o the supercharge.
My problem is that when i start the car it idles to 1000 to 800 rpm. Then when i drive it around and the car is warmed up and i stop at a light or sumthin the idle on it drops to 500 to 400 rpms.Also when i stop its a slight vibration. My checkengine light is not on. And i just put new spark plugs, ignition module, and crank shaft sensor on it, and still no change.

so if theres is anyone that can help let me knoe whats wrong or needs to be done let me know thanks.

change your spark plug wires. On startup, high idle is usual for the engine to lubricate itself. as long as it idles down to 500-600 after a few seconds, nothing to worry about there. Replace the wires, and the warmed up idle should improve.

well iput new wires on it and still no change.
I ran the car diagnoistics and the code was 22 which is to replace the TPS. If i was to do that would that change my idle? Also didnt the check engine light pop up if that is the problem?

TPS can cause rough idle. There are plenty of threads here on the subject, Do a little searching and you'll figure it out.

I hate to even bring this up, but with 157K you need a new timing set. The TPS sensor can cause problems also, however usually not an RPM fluctuation at idle. I have a 92 Ultra (165K) and had the same problem you decribed. Knowing better, I changed every thing ignition and fuel related hoping to find the cheap way out. Nothing worked until I changed the timing set, now she purrs like a kitten.

Sigh... yeah I have a 92 PA and it's been giving me problems ever since it got warm again. I live in Minnesota, and all winter long it ran pretty decent. Then it started warming up, and I have this problem where it runs OK for maybe 15-20 min, and then it starts sputtering. I'll hit the excelarator and it will start loosing rpms. I can feather the throttle, and keep up to speed (usually) but as soon as I have to slow down or stop the hissitates or dies. Getting back up to speed is almost impossible. Weird thing is... if I pull off the road, let it sit for maybe 15 minutes, the car starts up no problem and the rev-limitation is all but gone. I've changed the spark plugs, fuel filter, air filter, TPS and nothing has helped just like Buick Lover :banghead: :wtf: :swear:.

The check engine light never came on either, until I had a friend install new TPS. Then once that was installed, thats when the C-E light started coming on/off. Is there any way to figure out if it IS the timing? The guy I who did the tps now thinks it's either the ECM or Fuel Pump. I went out and bought the fuel pump, but haven't installed it yet (a lot of work). I'd like to be able to stop spending money on parts and just get it working for sure. So HottZ28, is there any way to figure out if it is the timing (cheaply)?
Other wise I'll feel just like... :nutkick:

Hey Moparz, that is one beautiful state you live in! I spent some time back in the 80’s in St. Cloud, Alexandria, and Albany in the winter and summer. I definitely prefer the summer though!!

Is the code you are getting now, still the TPS or somthing different?

Check the fuel pressure before you change the fuel pump! You can pick up a fuel pressure tester at a parts store and do it yourself, or if you know someone who has one, just borrow it. Hook up the tester to the fuel rail Schrader valve and turn on the key. Bleed out any air in the tester and start the motor. You should have anywhere from 38 to 48psi at idle. Anything below 38 would be marginal.
When I had problems with my timing set, (magnet) I used a scanner that I could monitor the timing while the motor was running. I had sporadic fluctuations at idle with the car in gear. It would bounce anywhere from 4 to 6 deg. below normal.

If it matter anything, it doesnt matter how it runs weather I have the transmision in drive/neutral/park. The engine runs poorly so I'm fairly sure I dont have a transmision problem. I'm thinking I'll take the fuel pump back and have someone scan the engine again. The last time I had the computer jumped (not scanned that time), the guy said it looked like it was saying either the ECM or FuelPump but wasnt sure. A week before I had it hooked up to a scanner and nothing showed up wrong... nothing like paying $85 for nothing :banghead:

So I brought it to a friend who jumped the computer after the TPS replacement and thats when things the light turned on. I hate cars sometimes.

And yes... minnesota is beautiful in the summer... I could live without the winters though lol. I'm from Minneapolis... but it's about the same all over.

Low fuel pressure will not show up on a scan. If you have a timing problem usually you will get a code 41 & 42. Since you did not have any codes prior to changing the TPS, your problem sounds more like fuel or EGR.