Recently I have been having issues with my car running a bit erratic, I was hoping someone on here has experienced the same or similar issues and can help. The car has problems maintaining a steady rpm, stalls on most extended complete stops, also has a tendency to stall when putting in reverse. I have already replaced the IAC, CT sensor, injectors, knock sensor, TPS, ECM and still can't find the cause for the poor idling. I also have problems in the warmer months with the car running hotter then what it should be. I have replaced everything in the cooling system except the heater core, including replacing the head gaskets. The car has a 160 thermostat, hypertech cooling fan switch which comes on at 176 and goes off at 166, I also have an extra electric fan pushing from the front to help but it doesn't. The car will still run around 220-230 in the summer on average, some days hotter. If anyone can help I would appreciate it. Tom

 

A bad enough vacuum leak can cause all those problems.

 

will it run ok before it is heated up? or if you put it in to limp mode?

 

I agree with TylerP. Check all of your vacuum lines. Also, when was the last time you replaced your o2 sensor? A bad MAF sensor will also cause some of those problems...

 

A puller fan will work better then a pusher too.

 

Wow... I just drove my car, (only 22,000mi), 20 miles to put away for the winter, and around 15mi into the trip. I came upon the same symptoms that you described. let me know what you find out. I didn't go through all the changes you did. Some time when i have time i'll work on it this winter.

 

it runs a little better when its cold, but it still has the same symptoms. I have replaced the O2 sensor a while back, but that was before I did all of the upgrades. I know my description was minimal so I will list the upgrades. The car has a Jasper 350 bored 40 over, 24 lb injectors, adjustable fuel pressure regulator, air foil, throttle body coolant tube bypass, msd coil, edelbrock headers and y pipe, no cat, smog pump delete, 3 inch flowmaster cat back, hypertech fan switch, hypertech thermostat, and hypertech thermomaster chip. The car is a 700r4, which has a B&M transpak, and billet servo, and the rear has an Auburn posi with Richmond 373's. I was thinking that maybe the car is running weird because of the exhaust and emission system changes without a custom chip, and it was just causing the ecm to over correct for certain things.
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Not that it matters now, but the car was originally a 305 tpi, I have replaced the factory prom with a prom from a 1990 iroc which was a 350 tpi, and I also replaced the 305 knock sensor with a new ac delco 350 sensor.

 

Well I dont know if this will fix, but I have had a problem with my 91 k1500 truck. Basicly when in gear (F or R) It will stall. I also have rpm surges. It was to the point that just steping on the break and turning the wheel it would stall also.. It did not throw codes either...

After many replaced parts. I found that the magnetic pickup coil in the distributer was putting out low voltage. It seems that chevy in the 80-90's had difective or weak magnents in the coil. The low rpm would cause a low output causing it to stall..

Its easy to check and cheep to fix. I just replaced mine for 12bux from autozone.. Gas mileage went up also.

see the link http://www.73-87.com/7387garage/drivetrain/pkupcoil.htm

 

Actually today I managed to get some time at the shop where I could mess with the car a little, so I changed the O2 sensor again, and also set the base timing. I have only driven the car about 6 miles to this point but I have not seem any symptoms return. Thanks to all those who responded with possible causes for the runnability problem. I will keep everyone posted on how it runs over the next few days. Thanks again. Tom