5.8 high idle saga continued

I made it through the weekend, and yes, it is still doing the 1500rpm 65 second runup during startup. However, several times it started normally. The weather has been dryer here the past 3 days, so maybe
that is a factor, I don't know.
To Tom Adkins and Lugnut (if you'd care to answer):
1. Do you think it could be a bad EEC? 2. Could it be a short somewhere? 3. Is it possible it's linked somehow to humidity change, ie some sensor sticking (TPS?).
I might throw another part at it.
Thank you, John
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In article

Look at the power steering pressure line between the P/S pump and the gear box, see if there is an electrical switch ported into the pressure line. If so, disconnect it and see if the symptoms improve.
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john wrote:

Offhand, If you're going to toss a part at it, I'd say TPS, Throttle Position Sensor. You're getting to a point where you will have to have it checked out, in person, by someone qualified to do a diagnosis. The TPS is a "wear item" that can cause all kinds of strange symptoms as it fails. It's ~$25 and will either solve your problem, or it won't. If it does not, it's time to bend over and see your local dealer (or qualified Indy Shop).
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Is the TPS just a bolt on - plug in part? Do I have to "set" it, or calibrate it?
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On Mon, 23 Jul 2007 17:01:57 -0700, john

I agree with Tom. I think the only part I would just throw at it at this point is the TPS. Fairly cheap and easy to change. They can get flaky and fail w/o setting a code. I have seen them hold 30-35 mph after the throttle was released and not set a code. You may want to pin the wires on it after you replace it to be sure the voltage at idle is correct. IIRC, it should be around 0.5 VDC. Around 1.0vdc, the ECM starts the off idle sequences to advance timing, increase fuel and other chores. The ECM's are pretty reliable and not prone to failure. More often than not, ECM's that are replaced do not correct whatever the problem might be. IMHO, the Ford STAR tester is more capable than any other tool on the market on Ford products. A knowledgeable teck should be able to find the problem with it. Most of the dealership in my part of the world will apply the diagnostic fee toward the repair. At this point, I think it is probably worth your time and money to get this done. There are cases where a temporary breakout box has to be installed to find the problem.
You may also want to follow up on 'cuda's suggestion because the ECM does increase idle to compensate for steering pressure. A stuck switch can do this and the check is quick. This should also show up on a complete diagnostic.
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where exactly is the TPS on a 95 5.8? This is a California truck, if that makes a difference.
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On Wed, 25 Jul 2007 10:05:23 -0700, john

Should be on the bottom of the throttle body. You will need to dismount the throttle body from the intake to get at it. The water hoses should have enough flex to avoid disconnecting them. You will probably have to disconnect the EGR valve assembly. The TPS is held on by a couple of Phillips head screws. They are usually pretty tight. If the TPS has never been replaced at 150K, it is probably due. They do wear because they move just like an old radio tuner every time the throttle is moved. The TPS is simply an old fashioned potentiometer that slides a contact over a coil of wire to change resistance.
See my post on the manifold. If you do one of these, yopu may as well do both. Gaskets, TPS and supplies are probably less than $50 to do both at the same time and you will be finagling several of the same parts to do either repair.
BTW, while you are working in that area, you will see an idle adjust screw on the top of the throttle body. Unless you know exactly what and how you are doing whatever, resist all temptation to touch it or change it. It is set using some very specific parameters and will have no effect on your problem.
Good luck
Lugnut
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