Hey all-
My '92 Bronco 5 liter is giving me fits. Every so often but not all the time
it refuses to idle. Restart it a few times and it works fine again. The
IAC valve is new, and the throttle body and injectors as well as other
emissions components have been gone through and cleaned. Plugs, fuel
filter, etc. are new. Doesn't give any codes. I've even taken it to the
shop, bnut naturally, it runs like a champ when they have it and they can't
find anyhting wrong with it. This ever happen to anybody else? I'm at a
loss.
Thanks! Dave

 

Is the defrost or A/C on at all when this happens? A/C work?

If the A/C system leaked out it's refridgerant it will cause the compressor to cycle on and off repeatedly which can cause an irratic idle and possible stalling.

 

Is it only when vehicle has been sitting for a long period of time?? If so perform an injector leakdown test (note clean injectors does not mean pintles are sealing). Is it starting ok, or hard starting (cranks for a period before turning over)? Once it turns over does it idle rough? worse when you give it gas? dies on its own? will idle smooth out if left alone, if so how long? If you shut down vehcile and attempt to restart shortly thereafter (ie < 10 mins) is problem reproducible? Need more info to troubleshoot this better. I hope a/c isn't on this time of year

 

Actually, the darn thing runs great. It starts right up, runs smooth, and idles exactly like it's supposed to until it decides it doesn't want to. It does it with defrost on or off. It does seem to happen more often while turning, which made me think the power steeering pump make be going bad and bogging it down. The other variable is that we are force fed oxygenated gas from Nov-Feb of each year. It seemed to start right when the switch was made, but hasn't done it in years past.

 

Bad batch of fuel perhaps. Does the idle problem persist from initial startup? Only when the engine is warm? Any other parameters that might be synchronous with the appearance of the problem?