Cant figure this out... maybe u can help
 

I have a 97 F250 4x4 with a 5.8 in it. 185000 miles but a beast, never a problem and usually runs great. Now about a week ago my idle went nuts, either it would idle at 1500 rpm or stall when you took foot off gas. NO CODES, or CHK ENGINE LIGHT!! Ok so I talked to a ford mechanic I know from the American Legion and he said probably I.A.C. or T.P.S. so I changed both. After following procedures to program new I.A.C. truck started and did idle better but not where it used to, also now check engine light is on and truck is almost undrivable due to transmission slamming when up shifting.
Truck always shifted smooth as silk and actually started shifting hard after installing the T.P.S. Any thoughts?


Thank You
Bobby

No codes at ALL? A 97 3/4 ton is OBD1 unless it's a California truck, so you should have at least gotten the system pass code (111) when you checked. And if the engine light is on now, can you try reading the codes again?

Stalling and revving like that sounds like a vacuum leak so check around for that and let's see what the computer thinks as well.

Also, you don't program a TPS. You can however adjust it's position slightly to change the output signal.

Yes to checking the codes.

Post them on your thread when can.

You may have an air leak somewhere.

97 F250
 

I did not say I programmed the TPS, I said I programmed the IAC which must be done when replaced according to Ford. No vacuum leaks, Pump is working fine. No codes still but chk engine light is on

AS Stated, NO Codes, No Leaks, I smoked all lines, air pump working,
Any other thoughts

Your check engine light is on now so you should have codes. I'd also be interested in knowing what procedure you did to "program the new IAC". Maybe "program" isn't the best description but obviously you did something so what was it?

For reference the TPS is a critical input to the PCM for correct transmission operation so it sounds like you got something installed wrong or you left something unplugged.

Okay, NO codes you say. That is not a good thing. As I mentioned above, even with everything in perfect working order you should still get a code 111. Can you tell us exactly how you tried to read the fault codes?

With the engine light on there WILL be codes stored if the computer is working normally. If it won't spit them out then something ain't working.

Per Fords instruction for IAC Setting: After installation unplug new IAC, Start motor, Turn steering wheel full left, full right and return to center, press brake for 2 seconds and release, turn on A/C for 10 seconds and turn off, shut off motor, plug IAC in start truck

If you do have a EEC-IV system (OBD-1) and more than likely you do in NJ.
1. You do not have a steering sensor on your truck.
2. The brake system does not have an input to the PCM Computer.
3. if you unplug the IAC the engine may not start or may die if at idle when you unplug it.

Most sensors you need to unplug the battery for the computer to relearn there values. The TPS is different as the the computer relearns it each time you start the engine. That is why you do not touch the throttle while starting the engine as it will mess up the TPS value.

On the other hand the actuators like the IAC valve do not need the battery unhooked as they DO NOT give the computer any information. Most if not all of the actuators are solenoids so the computer just adjusts what they control.

I do not know about the 1999 or newer Fords but your IAC does not need to be programed. You are playing with the Computer and not the IAC in your text.

Did they give you a instruction sheet saying all of this?
If so can you scan it and post it in this thread or email it to me at email address below in this post.

As far as the codes go you are looking for codes in the CM.

Thank you Bill, But the tech from Downs Ford in Toms River NJ stood next to my truck and instructed me step by step to move the wheel, step on brake, and turn on A/C. What I really think is the parts store gave my guy a wrong TPS that's why the truck is now shifting so bad. I am going to Ford tomorrow with the old TPS and IAC and match them up. Then Im going to return the junk my guy got me and try this again. I am an ASE Heavy Line tech for cummins and cat. So this is way off for me. Anyhow thanks for all your help, we will see what happens when I change out parts tomorrow. By the way, with the IAC unplugged the engine starts and runs fine at about 500 rpm. no stalling

My computer seems to go to sleep sometimes when I type and two words were left out of the above post. Namely "DO NOT".

It should have read:
On the other hand the actuators like the IAC valve do not need the battery unhooked as they DO NOT give the computer any information. Most if not all of the actuators are solenoids so the computer just adjusts what they control.

Your truck takes the same TPS from 1988-1997 and fits just about every other Ford truck from 1988-1997 also.
So there is very little chance that they sold you the wrong one. They may have sold you a bad one and that is common.

Let us know what you find out and good luck.