Idle surging and stalls...

[Blackcrow64]

Geeez... Its never as simple as you expect it to be... So I went out tonight since the Firebird was fixed and all and since I swapped batteries it has developed a horrible idle surge... So bad that it can't even stay running when I come to a red light or stop sign. Definetly not cool... But anyways, here is whats happening...

Altenator is putting out 14 volts no problem. But as I begin to slow down to come to a stop it starts dropping to about 13 volts and it surges down to about 200rpm and then up to about 1200-1500rpm. It does it a few times before I stop and then when I come to a complete stop it surges once more and then stalls out. Sometimes it starts right back up no problem, other times it cranks and cranks with no response. Give it a second and crank again and it fires right up and starts surging. I got it home here finally and tried messing with it in the driveway and go figure, the son of a bitch won't surge or stall...

Somebody please point me in a direction to go, cause I have too many directions in my head right now...

**EDIT**
I had this in the one thread but then I figured everybody would overlook it since that thread was pretty much done for. Also the fact that I guess this is sort of a seperate problem.

Anyways, today I was under the hood for most of the day and I can't find anything wrong. Altenator is 100% ok, battery is 100% ok. I just put a new cap, rotor, plugs and wires on it a few weeks ago. I also checked all of my vacuum lines for leaks and couldn't find any whatsoever... So now I'm scrapping the bottom of the barrel here... Do these motors have some type of idle control sensor that could be going bad? I'm just not sure what else could be causing this problem...

[FormulaLT1]

Yes they have a IAC right at the bottom of the TB. Sounds like a vacuum leak though. I would check the vacuum pressure if I where you.

[Blackcrow64]

Originally Posted by FormulaLT1

Yes they have a IAC right at the bottom of the TB. Sounds like a vacuum leak though. I would check the vacuum pressure if I where you.

Is there a special way to check the pressure? I popped one line off while the car was off and it was holding pressure in it just fine still...

[FormulaLT1]

Are 92 3.1's Speed density or MAF? or do they have both MAF and MAP like later units?. In either event you should scan the car and monitor engine function and sensor relay. Also check for stored codes. As long as it is holding vacuum, sounds like one of your sensor (or possible the IAC) are screwing you up.

[Blackcrow64]

They are speed density... Also I have no codes right now... This car is getting on my nerves.

Maybe I should just replace the IAC and see if that solves my problem? I'm not sure what else to check since I have no codes to help me out here.

[wrightz28]

2 ideas,

!-PCV and or hose problem.

2-Brake booster check valve and or hose problem.

Check the eingin vacuum out with a vacuum gauge, a decent engine should hold 12 hg. A good engine will hold more, and a worn engine less. What's most important is how steady it holds.

--edit--

This started after the batery replacemnt?

[Blackcrow64]

Yes, it started after I swapped batterys, so I have to give it this years WTF Award...

Now that I think about it maybe the brake booster check valve has gone bad. Because it only does it when I'm on the brakes coming up to a stop. Once I get stopped somewhere, if it doesn't stall then it will just surge unless I am in park... Where are the check valves located at on these setups?

[wrightz28]

On the booster, at the end of the vacuum hose.

[Blackcrow64]

Well... After much searching I finally took the initiative to go and work on this little problem... Gave it a test drive this morning and it was still doing it so I brought it up and started a few things... It pretty much got a little tuneup which helped tremendiously...

New cap, rotor, plugs, wires, and pcv valve... Cleaned the air filter and I have a fuel filter to put in if it gives me problems again... I need to do the fuel filter anyways, but I just figured I would wait since I haven't slept yet today for work tonight...

I just figured I should give the answer to this thread instead of leaving it hanging for the rest of time... I do believe the pcv valve was the issue here as it no longer surges when I stop...

If it starts again, fuel filter will be next I guess...

[carguy2779]

you might check the egr valve if its stuck open or close it will cause suring and such