Engine Performance problem
1991 Oldsmobile Silhouette 6 cyl Front Wheel Drive Automatic 131000 miles
I have a problem with my silhouette that is really baffling me. I do realize that some of the symptoms could be seperate issues, but the one I am really concerned about is:
Vehicle does start, but not as fast as when it is warm.
After the first start of the day, or after the van has cooled for at least 2-3hours. It idles at about 1100-1200 and then at about 30 seconds it starts to idle down to 750 but can take a good minute before it does. Then after I have driven the van for awhile and it is nice and hot (not overheating) I come to a stop light and the idle is at about 750 but then drops down slowly to about 600
I have replaced the o2 sensor, the IAC valve, map sensor, spark plugs, air cleaner, pcv valve and older emission tubing. It has had the fuel pump changed approx 1 year ago. The first time this happened the van died and I got a rich-o2 sensor and a bad map sensor fault code. I just changed them and figured if that wasn't the problem I'd at least know those were good. Codes have been cleared. A couple of times I have started the van after I have driven at least 20-30 minutes, gone inside and about 30-40 minutes later I go to start it and it starts, and the idles so low it died in about 3-5seconds- I start it after that and it starts and then idles up to 1100 and then comes down quicker than when its been started for the first time of the day. This has only happened 2x's in the past 2 months.
The van does not appear to be missing or running rough. No smoke coming out of the tail pipe. I do get the oil pressure guage-it also drops after the vehicle is warm-when the idle drops to 600-no light's come on-but its approx (under 40) it's a tad under the first mark.
I also have noticed that -at times- the voltage guage- I can see the marker slowly move back and forth.
I did not change the TPS because I would think that the computer would compensate and I would be feeling the difference. I had an escort one time where the tps was going bad and it would jerk while driving.
Could I have a bad thermastatic air control valve in the air cleaner?
Could it have something to do with the ignition or the distributor?
I don't want to be on the freeway stuck in traffic and have this die on me.
I'm totally lost here. Can you help?
Thanks for your consideration
have the same problem?
Tuesday, August 18th, 2009 AT 4:30 AM