Idles Too Fast!!!
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Senior User
Joined: Jan 2006
Posts: 194
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From: MTNS of NC
Idles Too Fast!!!
I have an '87 302 fuel injected that idles too fast.I've changsd the idle air control,and the throttle position sensor , all to no avail.Does anyone have any tips as to what might be causing this fast idle ? It idles anywhere from 11-1200 up to 14-1500,and its driving me crazy.I've asked a few engine guys around here and have gotten answers from,the little plug you remove from the dizzy to set the timing , to the harmonic balancer seperating.Anybody got any advise ?
More Turbo
Joined: Jun 2004
Posts: 690
Likes: 0
From: Sweden
Yep. The intake manifold gasket is leaking, under the intake plenum. Lets in air that can't be stopped by the closed throttle. It messed up the idle mixture too. The engine guys' theories sound pretty far off to me.
To check, with the engine running, spray starting fluid or preferrably propane from an unlit torch in this area. If the engine idle increases, it's sucking air.
If you do this job, replace the passenger side valve cover gasket if it's leaking at the same time. Clean the intake manifold interior especially around the EGR valve port. Also, might want to clean the injectors.
On an '87, if they haven't been replaced, the vac lines over the passenger side exhaust manifold will be cracked (replace with standard rubber tubing) and the vac reservoir "coffee can" behind the starting battery will be rusting out. Check the timing chain slack (this will cause power loss and LOTS of problems, including rough idle, though probably not fast idle).
To check, with the engine running, spray starting fluid or preferrably propane from an unlit torch in this area. If the engine idle increases, it's sucking air.
If you do this job, replace the passenger side valve cover gasket if it's leaking at the same time. Clean the intake manifold interior especially around the EGR valve port. Also, might want to clean the injectors.
On an '87, if they haven't been replaced, the vac lines over the passenger side exhaust manifold will be cracked (replace with standard rubber tubing) and the vac reservoir "coffee can" behind the starting battery will be rusting out. Check the timing chain slack (this will cause power loss and LOTS of problems, including rough idle, though probably not fast idle).
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