Odd RPM Problem - Please Advise
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Senior User
Joined: May 2003
Posts: 123
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From: Philadelphia
Odd RPM Problem - Please Advise
I have been having this strange problem with my 96 EB 351 since I drove from Philly to Boston and back a couple of weeks ago. When I am driving at highway speeds and take my foot off the gas the Bronco will coast for a second and then my speed and rpms will have a sharp and noticeable drop. RPMs will drop by about 200, speed by a couple miles per hour. What I was used to was the bronco coasting after I took my foot off the gas with no sharp drop. The best way I can think of describing it is as if I was coasting and then drove through a sizeable puddle. Has anyone ever had something like this happen and what could be the cause? Thanks for the help.
Freshman User
Joined: Apr 2004
Posts: 46
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From: Chillicothe, OH
I had the same problem in my other car and sometime the engine light would come on and then it would go off again. It was saying it was the MAP sensor but it turned out to just be the vacuum hose had rotted. I am not sure if your bronco has that hose or not but it might be something to check out.
Hope this helps.
Hope this helps.
Lead Driver
Joined: Sep 2002
Posts: 9,182
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From: Gateway to the West
Semperfi may be on the right track with the MAP sensor since you are dealing with a problem that rears its ugly head when you have a sizable change in manifold pressure. To be certain though, the codes would be the place to start just so you don't end up swapping components needlessly.
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Senior User
Joined: May 2003
Posts: 123
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From: Philadelphia
Just to follow up on this in case anyone ever comes across this thread in a search. I pulled off my IAC valve and it had a ton of carbon gumming up the spring on the plunger. I took some throttle body cleaner and a paper clip and cleaned the crap out of it. Problem solved, and I didn't have to drop the cash on a new IAC. 
