89 Iroc running rough

I have a 89 Iroc 350 tpi auto with 80k on the clock.... I'd had this car for years and never came cross this problem. My car runs rough at lower rpms, and idle. After you get going, it seem fine, but when I stop or go slow it does it again. If I put it in gear, hold the brakes, and give it a little gas to put it under a load, it breaks back very bad. last tune up was less than a year ago. I used accel 8.8 wires with Autolite Double Platinum plugs. I changed the fuel filter today hoping that was the problem but no luck there. If anyone knows what the problem is please help. This is my daily driver and it's killing me in gas.

are u getting any codes or check engine light lets start there

sounds like a faulty IAC that happens to me once in a while

I have a 89 Iroc 350 tpi auto with 80k on the clock.... I'd had this car for years and never came cross this problem. My car runs rough at lower rpms, and idle. After you get going, it seem fine, but when I stop or go slow it does it again. If I put it in gear, hold the brakes, and give it a little gas to put it under a load, it breaks back very bad. last tune up was less than a year ago. I used accel 8.8 wires with Autolite Double Platinum plugs. I changed the fuel filter today hoping that was the problem but no luck there. If anyone knows what the problem is please help. This is my daily driver and it's killing me in gas.


first test i would do is ohm my injectors.

I'm not getting a light, so no codes. I forgat to say that I did run the car a little hot one day about 240* but cooled it off asap. I'm going to change plugs this weekend, hoping that i may have burned one.

stupid question. but does it still have the EGR valve? Just saying. a stuck on of those can do what you are saying too (if it is stuck open)

I'm not getting a light, so no codes. I forgat to say that I did run the car a little hot one day about 240* but cooled it off asap. I'm going to change plugs this weekend, hoping that i may have burned one.

why start throwing parts at the car? why not trouble shoot it properly and find out the problem quicker and more cost effective than just throwing parts at the car.

A bad plug will not cause the symptoms you have described, neither will the IAC. An egr valve could at low rpm cruise, but not idle.
Your injectors however, can cause all the symptoms. :)

I never understood why people start these threads asking for help, just so that people who know these cars can HONESTLY try and help, then the OP just throws parts at the car anyway.

why start throwing parts at the car? why not trouble shoot it properly and find out the problem quicker and more cost effective than just throwing parts at the car.

A bad plug will not cause the symptoms you have described, neither will the IAC. An egr valve could at low rpm cruise, but not idle.
Your injectors however, can cause all the symptoms. :)

I never understood why people start these threads asking for help, just so that people who know these cars can HONESTLY try and help, then the OP just throws parts at the car anyway.

I have a blazer that had an EGR valve hung open... It has an extremely crappy idle, and crappy low rpm... was only good after 2000rpm. So an EGR Can do it.

But doesn't the EGR valve cause a light? Just to give you a better idea of whats going on. I know everyone at some point has ran there car a little low of gas, turn a curve and it starts to break back then it picks back up and smooths out... Well thats how my car does every time I take off. If i stop at a light for a long time, it gets worse. Longer I sit at idle the worse it gets.

why start throwing parts at the car? why not trouble shoot it properly and find out the problem quicker and more cost effective than just throwing parts at the car.

A bad plug will not cause the symptoms you have described, neither will the IAC. An egr valve could at low rpm cruise, but not idle.
Your injectors however, can cause all the symptoms. :)

I never understood why people start these threads asking for help, just so that people who know these cars can HONESTLY try and help, then the OP just throws parts at the car anyway.

Dude,evidently you've never had a fouled spark plug or an EGR valve stuck open b/c BOTH of them would cause bad idling/stalling and a fouled plug could cause it to backfire which sounds like hes trying to explain? Im not sure what "break back" means though.

But I do know what you mean though,tell them some things to check and they come back and say "well,i put new this this and this on it and it still does it" and they dont even try what you tell 'em...LOL,I just laugh.

Dude,evidently you've never had a fouled spark plug or an EGR valve stuck open b/c BOTH of them would cause bad idling/stalling and a fouled plug could cause it to backfire which sounds like hes trying to explain? Im not sure what "break back" means though.

But I do know what you mean though,tell them some things to check and they come back and say "well,i put new this this and this on it and it still does it" and they dont even try what you tell 'em...LOL,I just laugh.

Ive had plenty of both but a fouled plug would bog more likely than not, throughout the rpm range. Also he doesnt have any codes so probably not the egr either. Henceforth I told him to ohm his injectors.

FWIW i had the same issue and it was a bad injector.

i second that a bad plug is a bad motherfu#cker it will def do all that i just ran into that problem this month

It may sound crazy, but check your timing. You said that it hit about *240. Mine did the same thing and I checked the timing and it was a little off. Made the adjustment and no problem since.


Greg

How about a vacuum leak? Any one of a number of vacuum lines could be disconnected or loose. This would cause a terrible idle and would clean up with more throttle. Check your brake booster hose and several of the TPI hoses on the passenger side towards the rear - anything connected to the plenum assembly.

Good luck, hope this helps.

I have had EGR throw codes and not throw codes before... My blazer is a perfect example of looking all over to find out it was the EGR, and there were no codes when I would srat it up and it would idle or rev in park. the minute I got on the road and hit 55.. it would throw the code and darn near scare me to death. because a stuck EGR valve is like a big vac leak. IE. bye bye Power brakes.

Other things to check, EGR valve gasket. Vacuum line leaks.

bump

Update, I'm still have the same problem. But what i have figured out is that it maybe a weak fuelpump. I primed the fuel pimp by turning the key to on. I stuck a small screwdriver in the valve on the fuelrail. Hardy any gas came out. I tried starting the car, and same thing. I sprayed starting fluid in the trottlebody and she started right up but ran like crap and shut off. I had to use starting fluid again to get it started back. It has a new fuel filter on it, that was the first thing I tried.

a fuel pressure check would tell you if the pump is crappin out on you.

How much pressure should I have at the rail test port.

I think it is supposed to be around 40-45psi

Can some confrim that B/C I only have 36# . Thanks

I just did some checking on thirdgen.org.. looks to me that you fuel preassure is low. should be right around 40# avg with it idling and vacuum line off the regulator.

the spread is 43.5#-38# But most say 40# is where you would like it. looks like maybe your pump is not doing it anymore?

Thanks for the help , 89 iroc check your fuel pressure I may have found my problem .Sorry to hijack your post but when I logged on yesterday Your car is doing the samething as mine .You guys rock!:metal:

thats cool you just helped confirm what my problem is.

No problem.. all I do is read these forums and such.. Some things tend to stick ;)