85 c4 idle problems
 

Hi everybody, new here... My 85 c4 cranks fine, but after it warms up (Idling)it starts loping and shuts off, it also does this when I stop at lights. Could a leaking injector cause this? I checked the fuel pressure and it holds a constant 30 psi, I can disconnect the vacuum line at the fuel regulator and the pressure goes to about 38 psi. I've replaced most of the sensors except the air temp sensor under the plenum, and the coolant sensor in front of the engine above the water pump. Any ideas? Thanks in advance

RE: 85 c4 idle problems
 

Is the Service engine soon light on? Codes???

RE: 85 c4 idle problems
 

Hi and thanks for the reply. No codes at all, keeps flashing 12. When it's idling, it sounds like it stumbles a few times and stalls, hit the key and it cranks right back up and idles for about 30 seconds and stumbles a few times and stalls.

RE: 85 c4 idle problems
 

Would also like to mention that it runs fine cruising down the road.

RE: 85 c4 idle problems
 

Theres a idle adjustment on the throttle body. Crank it in for a faster idle.

RE: 85 c4 idle problems
 

OK, I've found the problem with the idle. Timing was too high, lowered the timing and the thing smoothed right out. Did encounter another problemthough, It surges at WOT from a dead stop until it reached about 60 mph then it smooths out and runs good. I disconnected the vacuum line to the EGR valve, and that took care of the surging at WOT. Is the EGR valvebad? I replaced the EGR solenoid switch but it still surges at WOT with the EGR vacuum connected.

RE: 85 c4 idle problems
 

You got the dreaded TPI vacuum leak. Betcha'!

RE: 85 c4 idle problems
 

Sounds to me like you ha foreign air getting into your intake[:@] but ill still put my money on vacuum leak somewhere get a vacuum gauge and see what it pulls at idle how steady it is my money is on it bouncing and dancing like a ballerina!!! good luck

RE: 85 c4 idle problems
 

OK, I checked the vacuum, it's holding steady at 20 psi vacuumat idle. The service engine light finally came on yesterday. code 23, manifold air temp sensor...and code 32,EGR failure. Could that causethe enginenot to idle back down correctly? It doesn't do it all the time, sometimes it idles down to 700 rpm, but sometimes it gets stuck around 1100 rpm and I have to shut it down and restart it to get it to idle down, it only does it after driving 20 miles or so and stop for a light or turning in the driveway. Like I said, it doesn't do it all the time. I've replaced the IAC valve and cleaned the throttle body throughly so I know thespoons in the TB arenot sticking. I plan on replacing the MAT sensor and the EGR valve this weekend, wish I had some new injectors to put in it, but thats just not in the budget right now :(

Thanks

RE: 85 c4 idle problems
 

well if you replace the egr valve(which is probable clogged) i think your problem will clear right up! its unlikly the injectors have anything to do with the problem, all the symptoms point to vacuum or EGR, replave the EGR valve and go from there, i believe your problem will be fixed:D:D:D