Idle Surge

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

Idle speed control motor is probably gunked up.

I checked the IAC Motor and it looked clean. Someone had suggested to replace the coolant sensor. It was only 20 bucks so i went ahead and replaced it. Seems to be running ok for now. I'll keep driving it over the next couple of days to see if it really fixed it. If it doesn't...any other ideas?? Also, does anyone make a programmer for the 90 camaro to adjust computer settings?

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??

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!!

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!!


Hmmm, sounds like an over heating problem to me. Check coolant, radiator, sensors, and as well hoses and wiring. is it TPI or carb?

It is TPI. It runs about 170 give or take. It might get up to 200 but thats about it. Coolant, Radiator and hoses all good.

It is TPI. It runs about 170 give or take. It might get up to 200 but thats about it. Coolant, Radiator and hoses all good.



Hmm quiet stumped with this one. I have a 1986 with a 305 but its carbed. One thing is might be is cat converter. If its cloged not much will flow through there and in term with have backed up exhaust and in that case die. It did it to me a few times. check the cat converter. Let me know what goes down and I'll help ya most I can.

Thanks for the idea but no cat on the car...I had it removed a while back just for that reason. Thanks though!!

Thanks for the idea but no cat on the car...I had it removed a while back just for that reason. Thanks though!!


haha well then. Hmm... I want to say something clogged but as far as that goes it's hard to figure out now.. nothing as far as you know has gotten into the engine right? like dirt, no old oil, metal shavings?

Nothing that I can think of. Is the TPS adjustable? Do you know if there is a way to test the IAC motor to see if it's bad?

Nothing that I can think of. Is the TPS adjustable? Do you know if there is a way to test the IAC motor to see if it's bad?


It should be, not to big on TPS but if I'm correct yes. As far as IAC motor you can clean it with a cleaner on a swab but to tell if its bad would be to look at it and see if theres any excessive wear or marks, as well as gunk.

Thanks Matt...I'll do some more work on it tomorrow...let you guys know what happens. Thanks for the help!!

Thanks Matt...I'll do some more work on it tomorrow...let you guys know what happens. Thanks for the help!!


No problem, oh while your on here I was wondering if you would now some good mods for a 305? I got headers, new air breather and exhaust. and other ideas on what would help with performance?

I've got all MSD ignition parts on mine, ignition coil, distributor cap, rotor, and wires. All those are pretty cheap. Not sure if you have messed with your timing, but you can advance your timing. I also have a performance chip installed in the computer. Don't know if you have a SMOG pump or not....I took mine off. Not sure if that really helps with performance or not. I don't know how far you want to go...I rebuilt my 350 bored 30 over, oversized pistons, and a bigger cam. Hope that helps.

I've got all MSD ignition parts on mine, ignition coil, distributor cap, rotor, and wires. All those are pretty cheap. Not sure if you have messed with your timing, but you can advance your timing. I also have a performance chip installed in the computer. Don't know if you have a SMOG pump or not....I took mine off. Not sure if that really helps with performance or not. I don't know how far you want to go...I rebuilt my 350 bored 30 over, oversized pistons, and a bigger cam. Hope that helps.


yeah it does, i took my smog off as well, but mine doesnt have a chip. I'll probably work on it more tomorrow.

Still having problems. 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

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??

Replace MAF Power Relay & MAF Burn off Relay

I had the same problem.

Some years, I don't remember which didn't have an adjustable TPS in stock form. My GTA was non adjustable, so I replaced with an adjustable. The voltage is too high, .52 +/- .02 volts is the sweet spot. Could also be the distributer out of time?

Finally fixed...I changed out the injectors and a vacuum hose. Right underneath the plenum is the EGR valve. Right on top of the EGR valve is a vacuum hose that connects to it. There is a little bit on the under side of the plenum that was pinching off the hose...that's why I couldn't find a leak. Thought u guys might wanna know. Now she's running like she should!! Thanks guys