Firebird Nation banner
1 - 20 of 23 Posts

·
Registered
Joined
·
14 Posts
Discussion Starter · #1 ·
I have a 1995 Firebird with the 3.4l the car runs down the road great but never wants to idle properly. It will run for a couple at an idle then want to stall but after a few sputters it comes back on it's own. New fuel filter gas lines full tune-up all have been done. Could I need to change the IACV?
 

·
Administrator
Joined
·
15,115 Posts
You may get better results if this is posted on the "All Things V6" forum, rather than here on a regional forum. I can move the post there if you want me to.
 

·
Registered
Joined
·
14 Posts
Discussion Starter · #4 ·
Put a new idle air control valve in my 1995 bird. Do I need to just install it and go or do I have to reset something cuz it really feels like it may have only made a slight difference???
 

·
Administrator
Joined
·
15,115 Posts
What led you to believe the IAC valve was causing the rough idle you described in your other post? How did you test it?
 

·
Administrator
Joined
·
15,115 Posts
Probably would have been best to post this as a continuation of your original thread. When I get to a PC tomorrow, I'll merge this thread with your earlier thread.
 

·
Administrator
Joined
·
15,115 Posts
You indicate in the first post that the engine "sputters", wants to stall, but then "comes back on its own". That sounds like the IAC is doing its job to bring the idle back up to the correct RPM. On the other hand, as vehicle speed/RPM increases, the PCM opens the IAC valve, to prevent the engine from stalling when the throttle suddenly closes. So it's a bit vague as to whether the valve is causing the problem. Once the engine recovers the correct idle speed, is the idle rough or smooth?

Ideally, get an OBD-1 scanner on the PCM and observe what the PCM is telling the IAC valve to do... it will show you the "steps" that it is open, from 0 to 160. Typically at idle you want the counts in the range of 20 - 40. That gives the IAC room to open and close to control the idle speed. As the vehicle accelerates, and RPM increases, the counts should climb closer to 100.

There is no feedback to the PCM as to whether the IAC is even working. And, even if it's working, it's possible that the air passage that the valve controls is partially plugged up.

Finally, when you swap the IAC valve, there is a "learning" procedure that may help. This is the procedure for the V8 valve - the V6 should be similar.

http://shbox.com/1/4th_gen_tech2.html#iac_reset
 
  • Like
Reactions: GaryDoug

·
Registered
Joined
·
14 Posts
Discussion Starter · #10 ·
It seems that replacing the IACV has taken away most of the trouble but the idle now seems to be a little high but it is smooth gonna drive it for a bit and see how it reacts after having a few miles on it. Thanks for the link Fred I am gonna check it out now. I am no mechanic but I get by.
 

·
Administrator
Joined
·
15,115 Posts
What is the idle RPM, engine fully warmed up - in gear, and in neutral? Typically GM sets it at 550 in gear and 650 in neutral for the auto trans. I'd have to check the factory manual for the 3.4L specs.
 

·
Registered
Joined
·
14 Posts
Discussion Starter · #12 ·
right around 900 in gear a tad higher in neutral but it doesn't seem to be really high. Acouple of videos I watched with the 3.4l showed the rpm around the same that mine is. A friend of mine told me to drive it a little bit, really have not gone anywhere with it,so I will let you know how that works out thanks again for that link. I tried the reset of the iacv. That seemed to have little affect. I don't really have all the tools and meters to do really deep searching.
 

·
Administrator
Joined
·
15,115 Posts
It seems that replacing the IACV has taken away most of the trouble but the idle now seems to be a little high but it is smooth gonna drive it for a bit and see how it reacts after having a few miles on it. Thanks for the link Fred I am gonna check it out now. I am no mechanic but I get by.
I only provided all that detail because you indicated "it really feels like it may have only made a slight difference???"

If in fact it eliminate all your trouble, it must have been faulty.
 

·
Registered
Joined
·
14 Posts
Discussion Starter · #14 ·
Still having the eratic idle. When you stop at a red light the car runs smooth then the rpm drop to a sputter putting the car in N sometimes clears it up but usually have to give it a bit of throttle to recover then the rpm shoots way up and stays there around 2500 or higher. Shut the car off and the idle is back down around the 850 or 900 range and it repeats itself revving way up high again. May just bring it over the garage and let them test it they have all the right tools. I am stumped on this one and the days of nickel and diming are over . The prices of all these little items is starting to add up. One thing I will replace tomorrow is the pcv valve I did miss that on the tune-up.
 

·
Administrator
Joined
·
15,115 Posts
Did you try the "reset" procedure?
 

·
Registered
Joined
·
14 Posts
Discussion Starter · #16 ·
Suddenly this car seems to be running just fine. And I did nothing. I did try the reset on Weds and I drove the car at least a hundred miles on Thurs and it still sputtered and even stalled on me. Drove the car on Fri. maybe 20 miles or so. Then today on Sat. the car seems to be running fine. Gonna let it cool down then try it again later see how it feels from a cold start.
 

·
Registered
Joined
·
14 Posts
Discussion Starter · #18 ·
Drove this car Saturday a few times on and off. It still gets it's sputters.. Went to change the PCV valve and found out it was just a rubber hose sticking up with a tube running to the air filter box. So the kid at auto zone gave me the wrong one my fault to I should have pulled it out in the parking lot. Gonna go get the right one maybe that will help????
 

·
Registered
Joined
·
14 Posts
Discussion Starter · #19 ·
So I got some throttle body cleaner today and thought maybe this tie something would happen. Cleaned it out really good. Car is 95% better. gonna hit it again tomorrow, as it was getting dark out. This will be okay?
 

·
Registered
Joined
·
14 Posts
Discussion Starter · #20 ·
Car seems to be running better. Someone told me to take the throttle body right off the engine and give it a good cleaning. How hard of a job is this and if I am gonna take it all apart would it be cost effective to just replace it. I have no idea what a new one cost. Is there one that is more high performance that I could install? For now I am just gonna drive it till I do some more research. Thanks for all your help.
 
1 - 20 of 23 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top