I have a 90 camaro Iroc w/ 350. The idle is surging up and down pretty bad and it likes to die. Doesn't do it all the time, sometimes it runs fine. Even at higher RPMs you can tell it's still surging a little. I just got done replacing the EGR Valve, Cap and rotor, TPS Sensor, plug wires, plugs, fuel filter, and the ignition coil. What else could it be?? Thanks

 

try testing the coolant sensor. that causes problems when malfuctioning, heres some back ground information that describes your situation. http://www.aa1car.com/library/coolant_sensors.htm Testing it with a volt meter and testing ohms is best way to determine if its faulty. A bad coolant sensor also affects the o2 readings. that website has some values

 

Can you tell me where the Coolant sensor is on the motor?

 

on my lb9 85' engine its on the front of the engine by the intake manifold. , its a two wire sensor. Yellow and black wires

 

Thanks...i will try that tomorrow and let you know what happens.

 

I have a 1992 RS with the 305 TBI and I am having the same problem. It comes and goes but the car will not idle and surges if you give it some gas. I have replaced the coolant temp sensor, but if the temp gauge is reading correctly then does that eleminate the temp semsor? I am fairly confident it is not a vaccume leak as i have checked it out several times. Any other thoughts? Fuel pressure regulator maybe?
New cap & rotor, wires.

 

can you rev it to keep the engine alive?

 

Yes I can rev it up, however it stumbles a bit. Would the fuel pressure regulater cause this? I am going to check every vaccume line on the car for leaks. Any other thoughts? It jumps from near 0 rpm up to about 2000 and back, like it is trying to correct a dieing idle. No SES light currently however it was on last week but the car was running fine.

 

I have replaced the coolant sensor and it seems to be running better. I'll keep driving it over the next couple of days to see if it really fixed the problem. If it doesn't...any other ideas?? Also does anyone make a programmer for the 90 camaro to adjust computer settings?? Thanks guys!

 

Also, I just checked to voltage on the TPS sensor and it's reading .75 volts with the ignition on without it running. Is that to high or should it be set right at .54 volts??

 

Not to hijack the thread but I think I may be having the same problem with my 91 w/305 TPI. At times when I start it idles a bit rough at first and then surgers to a little over 1000 RPM's. It settles back down and does not die. I drove the car on a humid day last week. Got home and noticed the coolant fluid bubbling in the resovoir container. The fan was not running. I turn the car on and off into the start position a few times w/o turning it over and finally the fan turned on. If I drive the car in the evening or when it is cooler out the temp rarely gets above 220-240. Does this too sound like a coolant sensor problem. Thanks so much, feel free to PM me as I do not want to take over Jcase350's thread.

 

Alright guys...turns out the Coolant temperatur sensor didn't work...still doing the same thing. I noticed that it only does it when it is extremely hot outside or the car has come up to temp. Any ideas? Could it be the TPS not adjusted properly. Also, the is a ticking coming from under the hood. The ticking gets faster as you rev the engine. HELP!!

 

Loud ticking increasing with engine speed? Hows your wires? Mine looked fine until I moved them around and seen large crack in it. Changed it out and my surge went away.

 

Mine ended up being one of the temp sensors. I brought it to a mechanic and he replaced the coolant temp sensor that I had just installed saying the scanner told him it was reading 45 degrees off at cold engine. He also found that a wire on another temp sensor had broke off on one of the heads, this I am glad he found as the cooling fan just had stopped working. Car runs OK now. I don't know if this will help anybody but file it under "for what its worth".

 

Good call on the wires. If i hadn't check the wires I wouldn't have found a loose spark plug. So the ticking(miss) is fixing. Still having problems though. It is still surging a lot and when I push on the gas the RPMs drop like it wants to die but as soon as they drop they come right back up and go. Getting tired of messing with this. I checked the TPS today and it doesn't have any place on it to make adjustments as far as I can tell. Is there a way to tell if the IAC motor is good or bad? Also, my Inflatable Restraint light is coming on. Would that mess with the car's performance? Thanks in advance

 

You've got a vacuum leak. Blow some smoke from a cigarette in through a vacuum line and watch where it comes out. Make sure to tape off the mouth off the throttle body or smoke will escape through the intake duct. It helps to use a very bright light.

 

Got out today and worked on it a little bit. I swapped the IAC valve with known good one...that's not the problem. Also, I verified there no vacuum leaks....what else could it be??

 

Surging is usually due to a lean condition. Ohm check your injectors and check your fuel pressure. Did you test for vac leaks with smoke, if not go back and test with smoke.

 

Yes, it IS due to a lean condition. My mechanic replaced the coolant temp sensor that I had just installed with a new one to solve the problem. I bought mine from the local parts store for about 10 dollars. His was a GM part number, cost 3 times as much but it did solve the problem. I guess you get what you pay for. Also the car would surge much less after it was warmed up to operating temp, which kind of confirms the coolant temp sensor.