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post #1 of (permalink) Old 12-24-2001, 09:04 AM
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Stalling at stops

I've had my '89 Bronco for 1.5 years. At first it ran perfectly. After a while, it began stalling when cold and would require 1 restart. Recently, it began stalling at almost every stop. When I re-start it, it idles fine, but as I come to a stop, it dips to 300 rpm, bounces back to 800 rpm, then dies. I have replaced plugs, cap and rotor, plug wires, and set timing. These have resulted in better and smoother acceleration, but no change to the stalling. Do any of you have recommendations on what to hit next?

Thanks

Don Bryant
89 Bronco XLT 351w/C6 stock
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post #2 of (permalink) Old 12-24-2001, 12:02 PM
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Re: Stalling at stops

Check the Idle Air Control (IAC) valve (mounted on the side of the throttle body) and the Throttle Position Sensor (TPS - mounted on the throttle shaft opposite the linkage). Haynes tells exactly which pins to probe, and exactly what values indicate OK. How many miles are on the oxygen sensor (HEGO)? Check it, too.


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post #3 of (permalink) Old 12-24-2001, 05:12 PM
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Re: Stalling at stops

Also pull your IAC valve off and check for carbon inside the two little ports and clean it out with carb cleaner if evident being careful not to get any in the IAC motor. Also check for carbon in the throttle body around the plates. you can clean that with just a clean rag dampened with carb cleaner wrapped around a long screwdriver holding the plates open with your other hand.



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post #4 of (permalink) Old 12-25-2001, 08:18 PM
 
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Re: Stalling at stops

Are you a hard breaker? The brake booster runs off of vacuum and if it had problems could stall the truck when braking.

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post #5 of (permalink) Old 12-28-2001, 08:50 PM
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Re: Stalling at stops

Steve, Broncomania, and Havack

I checked the IAC and it's readings were fine. I checked the TPS and the voltage was 5v no matter what position. I replaced it and cleaned out the carbon in the throttle body. It runs better, but not completely. If I decel. slowly, the idle will settle at 800 or 900. If I brake hard, it fluctuates between 500 and 800 and then settles at about 600. I also did clean the carbon in the IAC. Do you think the IAC could still be the culprit, or could it be the computer? How do you test the brake booster?

Thanks!

Don Bryant
89 Bronco XLT 351w/C6 stock
post #6 of (permalink) Old 12-28-2001, 09:17 PM
 
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Re: Stalling at stops

With the truck in park, quickly depress the brake real hard. If you have an idle change then you at least have a vacuum leak somewhere in the booster.

Havack!

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post #7 of (permalink) Old 12-29-2001, 12:10 AM
 
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Re: Stalling at stops

Sounds crazy, but check out your muffler and cats for restictions

A couple of times I've had poor performance, mileage and erratic idling and it's turned out that there was a fairly severe exhaust restriction. This is even more true for non-modified, stock style systems without the low restriction of aftermarket systems.

If you don't feel like gettin' cold and wet, take it into a muffler shop, almost all of them test that sort of thing for free and some actually have rel flow meters and specs for your application.

Sixlitre

p.s./
One other possibility, though not likely because it doesn't show up further up the rpm range, is fuel restriction.

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