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Old 01-23-2007, 12:13   #1 (permalink)
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1989 Grand Marquis Won't Idle

This is my first post on this forum and I did some searching on my issue. I have a 1989 Grand Marquis with about 303,000 miles on it. The car will not idle when stopped. It will run if you keep your foot on the gas and ride the brake. I pulled the IAC valve and cleaned it out with Brake Cleaner. It was fairly dirty. I made the sure the spring wasn't sticking and put it back on the car. The car will still not idle. Could this be an EGR Valve? I would think that the car should at least idle rough if the EGR is stuck.

Could I just increase the Idle on the car to keep the car idleing at a stop. The car will not idle if the engine is cold or warm.

Thanks!
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Old 01-23-2007, 14:30   #2 (permalink)
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Re: 1989 Grand Marquis Won't Idle

It sounds like the ISC motor is toast, However you need to check the ECM for trouble codes to confirm this before you start randomly replacing parts.
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Old 01-24-2007, 08:30   #3 (permalink)
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Re: 1989 Grand Marquis Won't Idle

Quote:
Originally Posted by 88grandmarq
It sounds like the ISC motor is toast, However you need to check the ECM for trouble codes to confirm this before you start randomly replacing parts.
Would the ECM throw a check engine light when the ISC fails?
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Old 01-24-2007, 10:58   #4 (permalink)
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Re: 1989 Grand Marquis Won't Idle

These older beasts are simple to work on. As already mentioned, you need to read the trouble codes from the computer. Replacing parts at random will only drain your wallet, and make you severely frustrated.

There are many things that can affect the idle, and one common problem is a vacuum leak. Considering the age of your car, and taking into consideration that many people won't touch the vacuum hoses until something goes wrong, I would check out each & every vacuum hose. I'm not saying this is definitely your problem, but if vacuum hoses have never been replaced, you are almost guaranteed you'll find some that are worn, brittle, or pourous. This is good preventative maintenance even if you discover all of the hoses are fine.

Also, I wouldn't touch the idle adjustment - this won't resolve your problem.
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Old 01-24-2007, 19:07   #5 (permalink)
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Re: 1989 Grand Marquis Won't Idle

yes, it will set a code

code 12 or 13 during the engine running self-test.
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Old 01-25-2007, 13:44   #6 (permalink)
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Re: 1989 Grand Marquis Won't Idle

I'll take a look at replacing some of the Vacuum hoses. Im not seeing a check engine light come on, but that doesn't necessarily mean anything.
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