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Old 03-20-2007, 07:56 PM
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Default EFI 460 Idle Speed Question

I recently bought a '97 F350 with the 460. The truck has 115k miles on it and the engine seems to run great. The only issue (other that a broken manifold stud) is that it seems to idle too high. Fast idle is around 1200 rpm, but it only drops down to 1000 rpm when warm.

I performed a quick tune-up on it which was limited to plugs, wires, cap & rotor, new filters, and cleaning the throttle body. None of this has seemed to help.

Any experience or advice on this subject would be appreciated.

Thanks :wink:
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Old 03-20-2007, 08:13 PM
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Try cleaning the IAC, it should be on the side of the throttlebody and look like this:



I know this is a Mustang picture but it'll real close to this.

All you need to do is take it off and spray the heck out of it with carb cleaner until all the crap quits dumping out of it and the movement is free and easy.
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Old 03-20-2007, 09:03 PM
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I will look for the IAC and give it a try.

Thanks
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Old 03-20-2007, 10:05 PM
pfm-64f100 pfm-64f100 is offline
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Default See if there is a code.

Good source for Ford EFI is http://fordfuelinjection.com/. They have stuff that will help you. I have learned a lot about EFI from that site. good luck
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Old 03-21-2007, 09:15 AM
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Double check for any vacuum leaks too. That'll bump it up a tad. I'm taking in all this 460 EFI stuff too, since I just bought a 97 F250 Super Duty. 8)
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Old 03-21-2007, 10:16 AM
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My 1990 has done the same thing since my it was new, and the dealership could never fix it back when it was on warranty. I just gave up and have been putting up with it. It doesn't set a code, and otherwise runs fine, so I just ignore it, although it is annoying at times... :x
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Old 03-21-2007, 10:43 AM
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Quote:
Originally Posted by John I.
My 1990 has done the same thing since my it was new, and the dealership could never fix it back when it was on warranty. I just gave up and have been putting up with it. It doesn't set a code, and otherwise runs fine, so I just ignore it, although it is annoying at times... :x
I was wondering if this could be normal... the truck runs great. I'm going to check the IAC this weekend, and if it doesn't help, I'll just quit worrying about it.

Thanks
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Old 03-25-2007, 05:45 PM
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Default TSB-91-25-7 idle air by-pass service kit

You might find this thread interesting:
http://www.ford-trucks.com/forums/33...urge-prob.html (My post is the last one on page 2.)
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Old 03-25-2007, 11:12 PM
ByronRACE ByronRACE is offline
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Default Idle speed issues

The throttle position sensor plays a role in older ford EFI systems, but in the case of yours...it will not, so don't adjust it.

The EEC looks at the position of the TPS at key-on and says "that's closed". In the earlier EECs, the voltage out of the TPS could effect idle quality.

A stuck IAC, incorrect base timing, misadjusted throttle plate, vacuum leak, or rich condition can all cause elevated idle. It is NOT normal.

That said, check your idle speed with a scan tool, not the factory tach. The factory tachs are usually VERY far off.

After that, I'd start looking for air leaks. Any hole between the MAF and the intake ports on the heads...even the size of a pencil lead...can do this.

Is your check engine light on? If so, what's the code?

Next, has anyone messed with base spark? Does this truck still have a TFI Ford distributor?

What do your long term fuel trims look like after 5 minutes at idle on a 160+deg F engine? If you don't have an OBD-II scan tool with datastream, you need one.

Let me know,

Byron
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