My 94 V6 Firebird runs great but since a few weeks it starts running less smooth after about 10 minutes driving: engine staals sometimes and runs poor when idling; like on 5 cylinders.
I noticed it has been taking some dirt because of a clamp not shutting off the air-intake completely (dirty air-valve) I also cleaned this small valve that regulates the warm air-loop and that seems to do some good.
Is there something else I must/can clean?
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is commonly caused by a dirty automatic idle speed control valve and
throttle valve but always run a OBD2 fault code as well as the
cleaning procedure. Buy a can of throttle valve cleaner (do not use
carburetor spray cleaner!) from NAPA or Carquest (made by CRC
chemicals) and spray it into the air intake while the engine is
running, use up about 1/2 the can, engine will try to stall hold the
speed up, shut it down and let it soak for 30 minutes, restart and
blow out the remaining fluid, shut it down and disconnect the
negative battery cable for 5 Min's to reset the base idle control
Sounds like the automatic choke is either binding or gone bad.
On a cold start, that's why the RPMs are bumped up for a few minutes...the choke is allowing the engine to warm up, before dropping the intake mix to normal "run" level.
However, should the choke remain closed once the engine is hot, the stalling will happen for lack of air.
The choke-control is mounted on top of the manifold, near the throttle cable-cam. Look for a small (about 3" wide X 2" deep) cone-shaped metal can with a linkage to the throttle cam.
With the engine off, spray the linkage at both ends with Liquid Wrtench and work the linkage in and out of the can a few times to check for smooth operation. You should feel slight back-pressure when you move the linkage toward the controller. With the linkage pushed in, spray and wipe the exposed surface inside the controller body.
Allow the cleaner to dry for a few minutes (it's just oil, I know...but if you used a spray, the propellants could be flammable) and start the truck. Allow it ti idle at least 5 minutes until the auto-choke pulls back on the throttle...then take a short ride around the block to see if that cured the stalling.
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If you haven't had the idle air control (air bypass valve) replaced or cleaned I would. The valves have a history of sticking cold. If you send more info like engine size and what fault codes are in the computer I could assist more.
My first guess would be a dirty carb/fuel injector set. Run some fuel cleaner through the tank and see if it gets better. You might have to do it through a couple of tanksful. How long since you've had a tune-up? It might just be that time.
The idle speed is not adjustable, it is computer (PCM) controlled, you can turn the screw for the hard stop, but the computer will just over ride that adjustment for the most part, what I think you may need to do is clean the throttle valve and the idle speed control air bypass valve, use carb spray, spray it in the intake with the engine running use the at least 1/2 the can, the engine will try to stall, keep it running, after you are done disconnect the battery for 10 minutes, reconnect and drive a few days so the computer (PCM) can relearn your driving habits and set the idle correctly based on your driving.
probably oil, it may be too thick when it's cold but once it warms
up it liquefies and your engine runs smoothly. you could try changing oil, I'm
guessing if you have a high performance oil the chances this is the problem may
be greater since high performance things are usually geared towards working well
when everything is hot