I just changed the EGR valve but no help..305 TBI 1992..very rough idle..hard to start..when starts idles ok for 20-30 seconds or so then almost stalls..sometimes stalls.any ideas?

 

Assuming the EGR and associated vacuum circuit are OK, it could be a faulty fuel pump causing the engine to run lean. How does it perform under load? Does it knock or break up/backfire out the TBI? The CTS will also cause similar symptoms if is mis-reporting the temp. Same thing if the MAP sensor is bad. There are alot of other things, but these are the most obvious.

 

Checked the MAP sensor..seems to be OK..does not backfire out the TBI..has this problem as soon as it starts cold..Replaced fuel filter and checked pressure ..OK..Could the timing jump..if it did would it have this problem?
Thanks

 

How does it run warm?

 

Can not tell..will not stay running long enough to tell..when it is running (barely running)and you hit the gas it stumples and coughs real bad out the exhaust!

 

Does it blow smoke? If not, it sounds like the engine is leaning out. A faulty CTS, bad fuel pump, or restriction in the fuel system would be some likely places to look. It could also be a possible ignition issue as well. Has it had a tuneup recently?

 

Mine did this. check to make sure egr valve isn't open. mine was related to a faulty egr solenoid allowing vacumn to the egr valve all the time.

 

A faulty O2 can also cause symptoms like this as well. It usually takes around 30 secs to around 3 minutes for closed loop. Once that happens, the engine will run lean if the sensor is bad and overreporting. Happens every now and then.

 

mine was doing the same thing i ended up replaceing the idle air control and coolent temp apperently the iacs just wear out over time and the coolent temp sensor was sending differant signals but looking at the gauge you would never known it was bad it was telling the gauge the correct temp but telling the ecm it was 50* hotter

 

At last..found the problem!!..faulty fuel pump..had to drop the tank..major job..labor intense..running fine again..thanks for all your input.