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post #1 of (permalink) Old 11-10-1999, 02:01 PM
Taylor
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From rough idle to dying/no start

'90 Bronco Fullsize, 302 5.0 EFI,
(had previous post on pg.7) Pulled the codes and it showed a bad oxygen sensor. Replaced sensor and truck still ran real rough. Checked the EGR valve with vacuum, when vacuum was applied the idle would get rough, and the egr would hold the vacuum. Also am getting the correct voltage to it from the computer.
When I cleaned the Idle Air Control Valve with carb cleaner and then put it back on it would run smooth for about 15 seconds the the idle would get rough again.
When I tried driving the truck it shook horribly, and finally choked to death down the street. So now it's totally dead and won't start now at all! It turns over fine but it won't fire up. I checked for spark and that's good so I figure it must be a fuel problem.

Also, Tried to get a volatge from the IAC valve but didn't get a reading, I want to be sure that part is it before I spend the $81.00 for it. Could the IAC cause a problem this severe?

Thanks in advance for any help!

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post #2 of (permalink) Old 11-10-1999, 04:39 PM
**DONOTDELETE**
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Re: From rough idle to dying/no start

Just an opinion, I think the IAC valve could do it. When it's wide open, it allows quite a bit of air to bypass the "butterfly" valve at the air inlet. You probably know, the voltage you're looking for would be coming from the plastic plug attached to the harness, not from the valve itself. Why not take the IAC valve off again and see if it seems to be stuck internally?
PS, how much did you pay for the o2 sensor, and was that a dealer price?


NormSpeed
post #3 of (permalink) Old 11-10-1999, 09:32 PM
Taylor
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Re: From rough idle to dying/no start

Thanks, I'll check again tomorrow on the IAC...The o2 sensor was $60 and I got it through the car quest.

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post #4 of (permalink) Old 11-11-1999, 06:48 AM
mudmonger
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Re: From rough idle to dying/no start

>>>>Hey Taylor, I know this is a little late, but, there is a web site-www.wrenchead.com-they have the best on-line parts store I have seen. I looked for O2 sensor for my 89 5.0 and they had it for like 40 dollars and will probably beat prices for other sensors as well. I like their prices better than Autozone. Also, if the sensor thing doesn't pan out, give the timing chain a look. This would cause the same problems you are having. If the chain is wore enough it will jump teeth. About 2 or 3 teeth would be enough to keep it from running or starting. You can pull the distributor cap to see if the rotor is even being turned when the motor cranks(if it doesn't the chain has broke). When the #1 piston is topped out the rotor should be pointing directly at that cylinder. If not, chain has skipped. Good luck to ya. Later.

NUFF SAID
post #5 of (permalink) Old 11-11-1999, 11:39 PM
**DONOTDELETE**
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Re: From rough idle to dying/no start

Couple other things. I'm just a shade tree boy but I have access to some Ford service bulletins--After you do any parts replacing, you should clear the KAM (keep-alive memory) by disconnecting the battery for at least 5 minutes. Then, drive for at least 10 miles. The engine may run bad for a few miles, but by then it will store new data in the ECA (electronic control assembly)and running should improve. Also, the service bulletin on cleaning the Idle Air Bypass valve gets kinda particular about how and where. They mention that you shouldn't try to clean the throttle body bore/plate area. They also say you should not run vehicles with air-flow meters during cleaning procedure. Last, they say to use Ford Carburetor tune-up cleaner but nothing else.

NormSpeed
post #6 of (permalink) Old 11-12-1999, 05:33 AM
**DONOTDELETE**
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Re: From rough idle to dying/no start

Hey mudmonger, it could be the timing but if the rotor isn't spinning then he really wouldn't be getting any spark, right??? so either the timing chain has slipped some teeth and has caused the timing to go out of wack (along w/ the valves, be carefull w/ that) or it would be a fuel/mixture poblem. make sure the duraspark is connected too.

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