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post #1 of (permalink) Old 10-19-2006, 08:11 AM
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Rough running at idle?

I have a 93 bronco 5.8 EFI. It started running rough intermitently at idle. I changed plugs , wires, cap, flushed the fuel and ejectors and I have plenty of fuel pressure. I replaced the Idle air control valve several times with some minor results. However I put the $130 ICV from the dealer because I was talked into it believing the othe $60 part where inferior, but no improvement. I believe it is somthing to do with the computer, sending, conections to the idle air mixture because the engine codes show a lean and a rich reading when put on an analyser. Any next best guess. The shops I have taken it to can't seem to find it because it is intermittent. I was hoping someone would be able to help me guess rather than pay a shop $60 hr or more to guess. I am getting desparate and thinking about a Toyota
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post #2 of (permalink) Old 10-19-2006, 10:11 AM
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Re: Rough running at idle?

did ya check for vacum leaks,egr valve,pcv valve,or lastly do a compression test to see if ya got good pressure on all cylinders..I'd check all vacum hoses first cause if one is cracked it'll leak some times then other times its fine...when it runs rough try wiggling wires and hoses under the hood thats how I fixed one of my trucks after the shop said there was nothing wrong with it,I found a cracked vacum hose...Hope it leads ya in the right direction...
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post #3 of (permalink) Old 10-20-2006, 12:21 AM
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Re: Rough running at idle?

My 1990 Bronco does this and I have always found it to be the coolant temp sensor. Sends a signal to the computer of whether or not the engine is cold or warm. Hence the lean rich reading. Just a thought. Also check for a vacuum leak around the throttle body gasket and one other place, the left front upper intake plenum bolt area. I've seen alot of these have a crack right above the bolt. I've replaced two on my Bronco in the past.
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post #4 of (permalink) Old 01-10-2007, 02:41 PM
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Re: Rough running at idle?

Thank you all I have tried many of your suggestions. I have run about 60 gal of premium(92 octane)fuel with Lucas(R)brand additive. The problem has almost comletely gone away. My suggestion, TRY THIS FIRST! I was told Sea Foam (R) additive works well to.
post #5 of (permalink) Old 07-24-2009, 12:06 PM
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i have a 94 bronco i had 2 replace the TPS throttle poising sensor.don't know if i spelled that right?
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