'99 Explorer Fast Idle
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Junior User
Joined: Sep 2000
Posts: 67
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From: Kingsport, TN.
'99 Explorer Fast Idle
My brother has a 1999 Explorer with a 4.0 SOHC engine and around 75,000 miles. When the engine is started it idles about 800 rpms. After it sits and idles for about 1-2 minutes it picks up to about 1200 rpms and will not come down, even in drive or park. We checked for vacuum leaks and also changed the IAC valve. The voltage on the IAC wiring connector was 11.3 volts. Anyone have an idea what could be causing the fast idle. Thanks.
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Joined: Nov 2004
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I have seen faulty ect sensors telling the pcm all kinds of diffrent readings causing bad driveability. Also have seen intake gaskets harding up causing unmetered air. This after awhile is followed by a check engine light.
J Marr
J Marr
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Junior User
Joined: Sep 2000
Posts: 67
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From: Kingsport, TN.
My brother took it to the local Ford Dealer and they told him the thermostat had came apart. They replaced the thermostat and it fixed the problem. He was charged $190 for finding the problem, thermostat and labor.
Senior User
Joined: Apr 2004
Posts: 190
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From: Las Vegas, NV
I was wondering what had happened with you guys. you may also have noticed odd shifting points under these conditions. although you could have saved a lot of $ if you'd done the job yourselves, this was a relatively simple and cheap fix compared to some of the others. glad you're back on the road safely.
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Joined: Jun 2004
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98 Explorer 78KMine started doing this (1400 RPM idle). I pulled and cleaned the IAC Idle Air Control Valve and disconnected the battery to reset the computer. Worked fine.
Next day it overheat ed on highway. Thermostat split in two. Funny how the two are linked and the miles are similar.
Now I need to know how to burp the coolant system??
david
Next day it overheat ed on highway. Thermostat split in two. Funny how the two are linked and the miles are similar.
Now I need to know how to burp the coolant system??
david
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Senior User
Joined: Apr 2004
Posts: 190
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From: Las Vegas, NV
did you drain the whole radiator or just get enough coolant to do the t-stat job?
In any case, with engine off and cap off radiator, fill radiator with your coolant mixture as much as you can. then start the engine and get it up to temperature, so that the new t-stat opens. Add coolant to radiator as needed with the engine still running. careful of fan belts/fan. turn off engine, replace radiator cap and add coolant to overflow res as needed. You might check it at least one more time after driving a bit to see if more coolant was still drawn in from the overflow tank and add coolant as reqd
In any case, with engine off and cap off radiator, fill radiator with your coolant mixture as much as you can. then start the engine and get it up to temperature, so that the new t-stat opens. Add coolant to radiator as needed with the engine still running. careful of fan belts/fan. turn off engine, replace radiator cap and add coolant to overflow res as needed. You might check it at least one more time after driving a bit to see if more coolant was still drawn in from the overflow tank and add coolant as reqd
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