Random High Idle/ Rich Mixture
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Joined: Mar 2002
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From: USA
Random High Idle/ Rich Mixture
I'm running a 1988 Bronco w/351 EFI. Lately my truck as been going in to high idle while i'm driving or the truck is in park. I have put a vaccume gauge on and it hold steady around 20psi. The problems occur after the engine has heated up. I have replaced the O2 sensor, Idle Air Control valve and throttle postion valve. I'm wonderin if it is runnin rich cause the inside of the exhause pipe if very black and not tan or brownish and if the engine is hot and i shut it off it is difficul to restart it. I have to depress the throttle all the way like it was flooded. i have beed told that i could be a cloged Cat or my MAP sensor is bad. Thanks for any help that u can provide
Tuned
Joined: Mar 2001
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From: California
Random High Idle/ Rich Mixture
[updated:LAST EDITED ON 17-Mar-02 AT 06:26 PM (EST)]I'd agree that the cat could be clogged that would explain the high revving( the computer compensating for the back pressure) and the difficulty starting when hot. If it has been that way for awhile the egr could be involved too. Have you run the codes? I know that may not be the technical answer you're looking for but maybe it'll help get you started. The reason I think that could be the case is it sounds similar to other situations I've ran into with other Broncos. Good luck and post if you need some help.
By the way you can bang on the cat to see if you here anything loose in there. As for the map could be but I can't see why that would give you difficulty starting when hot.
By the way you can bang on the cat to see if you here anything loose in there. As for the map could be but I can't see why that would give you difficulty starting when hot.
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Joined: Feb 2002
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Random High Idle/ Rich Mixture
Pull your plugs and look at them. That way you can see if its actually runing rich. If the insulator tips are not grey or white, or if it looks like there is a lot of build up on the plug then it may be a fuel problem. Check you cat's first though. Also try running some fuel injector cleaner through your system.
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From: USA
Random High Idle/ Rich Mixture
OK since my last posting this is what i have done and still have not solved my problems... Replaced EGR and pipe from manafold to EGR, MAP, Fuel pressure regulator, Check valve and crossover pipe for the smog pump <Check valve had separated from the pipe>, Intake air temp sensor. and cut off both cats... i'm runnin outta ideas .. i took the truck to the local ford dealer and they told me to replace just about everthing that i have already replaced needed to be replaced??..... the last thing that we can thing of it the TFI (thick Film Igition} Module but what i have read when those go bad the engine doesn't run at all.... anything that anyone can think of will be helpful...
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