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Discussion Starter · #1 ·
86 bronco xlt 5.0 efi

OK so this afternoon I go get in the bronco and the idle is terrible. I have checked for vac leaks and can't find any. When it starts the tach needles bounces up and down like it is on a yoyo. It does eventully even out at about 800 but sitting at a stop light in gear it has a pretty steady miss. Also before you drop into drive or reverse the idles sounds like it is going slightly up and down. I can hear the feul pump kick on and it does while moving not miss at all. Has a ton of power just when stopped it acts up.

Here is a video of the bronco starting up so you can see the tac bouncing up and down.

http://www.youtube.com/watch?v=-ZX1OUzEvPw

Also the tach does not bounce like that all the time. Normally when starting it shoots up to just above 1000 and drops down to like say 500 or 600 then stops at about 800. Your thoughts?
 

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my stang does it sometimes too, you can try cleaning your iac, that affects idle alot and maybe the voltage your tps is putting out...

my stang is wierd, always had idle problems, did an intake swap and it was perfect for 5k miles, and now it does it again...

it could just be the ecu idle searching... or maybe a need of tune up
 

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my bko ate my money
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i had an F150 that did this too we replaced everything posible b/c it was a new motor, couldnt find any faults it just did it

we ended up parting that one out and found out afterwards that i had put a 95 motor in a 93 truck, i didnt know the firing order was different but if you look in haynes it clearly states it:banghead
 

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Discussion Starter · #5 ·
Sweet, thx fellas. I did the IAC clean and the problem is almost gone complety. Heck the small miss at a stop light is gone. Also I found a hose off on the back of the intake which I did not see before. FYI, I put it back on before doing the IAC cleaning and it made no difference. Used to buck at around 3500 to 4000 rpm and that is gone. I can pass people again..lol I plan to do the six- liter upgrade this tax season as well as the 3g too :) Till then I can deal with a small bounce when starting. Thanks again all :)
 
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