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1997 Explorer idle problems

Old May 19, 2007 | 11:59 AM
  #1  
leafman13's Avatar
leafman13
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1997 Explorer idle problems

4.0L engine
The problem started after I went out shut the car off, then when i went to start it again, it was running rough and the idle was up and down.
I found that I had a dead spark plug, so that cured the rough running part, but the idle was still not right.

When I first start the car when its cold, it revs up to about 2000 Rpm for 1 min or so, then gradually drops down to idle, when I hit the throttle, it revs up, but it slowly comes down to idle.
When I am driving down the road, I can cruise at 40 kmph without touching the gas.
I read that the Idle control valve is a common problem, so I was able to get a supossidly good used one and it didnt change a thing. also i was thinking vacuum leak, so I used accetylene and found no leaks. Also though there were a few spots I could not get to.
Any suggestions would be very much appreciated.
 
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Old May 19, 2007 | 12:45 PM
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I had the same problem with a 93 T-bird. Took off the IAC idle control valve and it was burned up. Replaced it and things went back to normal, but not completely.
Idles fine at 750 rpm, I set the engine timming at 10 degrees TDC. That helps a lot.
I used the old gasket, thats the mistake. There are no short cuts.

The valve was $95.90 local of $71.76 on-line, but shipping will add $9.00
What does the old one look like. The inside is plastic.

Cleaning the valves isn't reccomended.
Eventually most of the senors go to sensor heaven it doesn't hurt to replace them as needed. Be sure and use a "new gasket".

A dead plug?
 
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Old May 20, 2007 | 01:07 PM
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After you replaced the idle motor, what was it doing???
and did you totally fix the problem by replacing the gasket?


the dead spark plug caused a misfire, after replacing it, the engine ran smooth, but still had the idle problem.
 
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Old May 20, 2007 | 01:42 PM
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Originally Posted by leafman13
4.0L engine
When I first start the car when its cold, it revs up to about 2000 Rpm for 1 min or so, then gradually drops down to idle, when I hit the throttle, it revs up, but it slowly comes down to idle.
When I am driving down the road, I can cruise at 40 kmph without touching the gas.
Any suggestions would be very much appreciated.
I have been chasing the exact symptoms all winter, IAC did not fix it and no Vacuam leaks. Have checked everything. Had it connected to the LT for a week, cant find anything out of spec.
I am of the mind to pull/test the injectors, might be one leaking/sticking.
 
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Old May 21, 2007 | 01:34 AM
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Talking

Originally Posted by leafman13
After you replaced the idle motor, what was it doing???
and did you totally fix the problem by replacing the gasket?


the dead spark plug caused a misfire, after replacing it, the engine ran smooth, but still had the idle problem.
Pretty much its as it should be, idles at 650, starts at 1500 cold, drops to 1000 then settles in at 650. The new gasket helped. The old IAC was burned up the plastic on the inside was melted.
It fixed my car. The problem started with a blown head gasket, which lead to the 0.2 sensors going bad, and the IAC getting too hot.

After two new head gaskets the car ran bad, till I got the 02 senors and the IAC.

Before I installed the new IAC the car started at 2000 rpm, dropped to 500 rpm but when you stepped on the gas the engine rev'd to 3000 and stayed there for a while and then gradually it dropped to 2000 and then 1000 and then to 500 rpm.

On this car the new 02 senors and the IAC and setting the timing to 10 degrees tdc made a world of difference.

It seems one thing leads to another. The good thing about Fords is they circle the problem.
 
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Old May 21, 2007 | 08:23 AM
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My IAC looked in good condition, and I found link on how to check it out by measuring resistance and my IAC is ok. When I step on the gas, it revs up to 2000 rpm, then gradually drops to idle. I measured the voltage to the IAC and it increses as well, so I know it is being told to increase RPM, so it is not the IAC.
I need to do some wire tracing to see where the signal comes from.
 
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Old May 21, 2007 | 09:58 AM
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Originally Posted by leafman13
My IAC looked in good condition, and I found link on how to check it out by measuring resistance and my IAC is ok. When I step on the gas, it revs up to 2000 rpm, then gradually drops to idle. I measured the voltage to the IAC and it increses as well, so I know it is being told to increase RPM, so it is not the IAC.
I need to do some wire tracing to see where the signal comes from.
Doesn't the signal comes from the EMC?
 
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Old May 26, 2007 | 01:41 AM
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remove the air inlet tube hold the throttle wide open and look at the throttle plate and around the bore were the plate sits when at idle. If it is all black and sooted up take a tooth brush and carb and choke cleaner scrub both the plate and bore clean. then remove the ground cable from the bat and hold it on the pos bat cable for 30 sec this will clear the keep alive memory ( ilde/ fuel control)and reset the pcm .good luck
 
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