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Discussion Starter #1
so ive now got the third engine in the bronco within a 6 month period. Its a 88ish 351 out of an F-350. Im happy to say that the damn thing finally drives, and runs ok, to a point. Its worth noting right now that the timing is still not set perfectly, and the engine still hasnt been run a lot.

Anways, i think that the TPS is screwed up or something. first, throttle response is crappy, but i would imagine this is because the timing is still a little bit off. The real problem is when i hit the go pedal and then release it. The engine doesnt drop back down to its normal 800ishRPM idle, instead it holds at about 1500RPM. After holding for a couple seconds it drops down to 400-500RPM and nearly stalls. After struggling at that RPM for a second or two it slowly climbs to a normal healthy idle.

Any ideas as to what could be causing this? check engine light isnt on and all vitals seem in check, but i could have missed something.

Thanks,

SM
 

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It could be a dirty IAC; I'd try cleaning it.
 

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CheeseBurger Milkshake!!
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Pull codes regardless--just to make sure. Make sure the timing is set correctly and clean the IAC.
 

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Discussion Starter #5
helmut, i would suspect a bad seal somwhere if the idle issue were continuous, but it only holds 1500 for a few seconds, then drops down to 400-500, nearly stalls, and then goes to the normal 800rpm idle and seems to run fairly well.
 

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A hanging idle like you described is usually caused by a lean condition. Double check vacuum lines and seals for air leaks.
No.


Like he described, it's usually caused by a hanging IAC on our trucks.

Cleaning seems to either help it, or kill it. Either way, look into a new IAC.
 

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Discussion Starter #8
i dont have a number on what the vacuum is, a friend of mine let me do the work in his garage so i didnt have to work in the snow. He took the vacuum, oil pressure, and compression numbers for me and said they all checked out fine.

Im away from the bronco for a week or two but when i get back i will hopefully take a lookat the IAC.
 
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