1984 Ford LTD (5.0 TBI) Idles High Until Warm Up


Old 01-11-11, 09:26 PM
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Smile 1984 Ford LTD (5.0 TBI) Idles High Until Warm Up

I recently repaired a Ford LTD for a friend. It had been sitting for a few years. The fuel had turned into varnish and clogged the fuel pump as well as the fuel injectors. I have since replaced the fuel tank, fuel pump and throttle body (with the injectors) from another one at the junk yard. Later discovered that the ECU was not firing one of the injectors, so I replaced that one as well (with a factory remanufactored junkyard ECM). The car has been driven daily for the past 3 weeks. Their only complaint is that, it idles high until it warms up. They're concerned by its "unintended acceleration". After I had replaced the ECU, I noticed that when I'd first start the car (especially when I'd connect the batter), the engine would idle quite high (2-3K RPM according to Hear-ometer). After 1-2 minutes, I would rev the engine momentarily (to probably 4-5K RPM) which would help it calm down (1500-2K RPM). If I revved it again a little later, it will go down to normal idle. I'm now being told that it takes 10 minutes to calm down/warm up (I'm not sure if they do they rev it).

Can anyone tell me if this is an issue with the car, or was it designed that way? And if it is an issue, what could be the culprit?
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Old 01-12-11, 04:09 AM
the_tow_guy's Avatar
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Not sure what it looks like on your beast, but I think I would start with the idle air system/control/valve.
Old 01-12-11, 07:43 AM
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Location: North Central Indiana
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high idle

If you are in a cold climate some of this would be normal. Of course if it is excessive then you have other problems.
Old 01-12-11, 07:29 PM
ukrbyk's Avatar
Join Date: Mar 2010
Location: USA/ Pacific NW
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well, it's fuel injected, so there's idle speed control solenoid somewhere on the throttle body. disconnect the plug to it and see what happens. mine went bad and decided to accelerate the car on frwy.

though it is normal for engine to warm up with higher idle, 10 minutes and 3 000 rpms is very excessive.

my 1st thought will be, loose throttle body gasket. sucks air in somewhere, until metal expends and closes the gap. start engine, and give quick shots of brake cleaner all over the gaskets. if it chokes, you found the area.

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