low/rough idle and dies
10-22-2004, 09:51 PM
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low/rough idle and dies
Hello all,
I am having some trouble with my 91 firebird formula. It appears to be idling too low (around 500 RPMs while in drive) and stumbles as I sit at a light and will die on occasion because of this stumbling/surging. I recently replaced the plugs, wires, idle air control valve and idle position sensor but no luck in solving the problem. The throttle body does not allow manual adjustment of the idle screw unless I am not looking at it right, so I cannot up the idle that way.
Could this be a vacuum leak? I recently noticed that the heater/air controls don't work like they should. The flap does not move the air completely to the A/C vents when the A/C is turned on and no matter what I put the controls on, air comes out of the defrost vents. Also, it sounds like a slight hissing when I switch it to "vent"
Is this feature vacuum controlled? If there is a leak, where would it be and how do I get to it? and would this be enough to cause the poor idle?
Thanks in advance.
-Chris
I am having some trouble with my 91 firebird formula. It appears to be idling too low (around 500 RPMs while in drive) and stumbles as I sit at a light and will die on occasion because of this stumbling/surging. I recently replaced the plugs, wires, idle air control valve and idle position sensor but no luck in solving the problem. The throttle body does not allow manual adjustment of the idle screw unless I am not looking at it right, so I cannot up the idle that way.
Could this be a vacuum leak? I recently noticed that the heater/air controls don't work like they should. The flap does not move the air completely to the A/C vents when the A/C is turned on and no matter what I put the controls on, air comes out of the defrost vents. Also, it sounds like a slight hissing when I switch it to "vent"
Is this feature vacuum controlled? If there is a leak, where would it be and how do I get to it? and would this be enough to cause the poor idle?
Thanks in advance.
-Chris
10-25-2004, 01:19 AM
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Car: 1984 Camaro Z28
Engine: 305 V8 High Output
Transmission: 700-R4
im sorry that i cant help, but im having the same problem. a lot of hoses are missing on my car but it runs decent except for the a/c and the tranny. you probably just have to hook up a few hoses, but im not sure. tell me when you find out whats wrong.
10-25-2004, 07:23 PM
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Car: 1991 Trans AM GTA
Engine: 5.7L TPI
Transmission: 700R4
When you replaced the IAC Valve, did you clean out the TB and the area under the TB where the valve is? If not, you might want to do that, it could be keeping it from working properly and not allowing enough air in. I had a problem similar to this and all I did is got a can of B12 and cleaned the valve and the TB really good and the problem is no more.
10-25-2004, 08:05 PM
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Car: 1988 Pontiac Firebird Formula
Engine: 5.7 TPI
Transmission: 700R4
For the idle problem, there is a really good tech article on setting minimum air, and TPS on this site. Read that over, and then you should be able to take care of those two little problems.
The HVAC controls are indeed vacuum operated. (fix this first.....) At the back of the intake, on the passenger side, is a selection of vacuum lines, check to make sure these are all connected. If you do a search, I think you can even find where someone posted a vacuum diagram here.
The HVAC controls are indeed vacuum operated. (fix this first.....) At the back of the intake, on the passenger side, is a selection of vacuum lines, check to make sure these are all connected. If you do a search, I think you can even find where someone posted a vacuum diagram here.
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