Alright, so some of you probably have seen my previous threads, and know I'm having idle/TPS issues. Well let's take it one step further.

To start, it was very recently running real good, decent rpm drop, smooth 650 idle, slightly sticky throttle. Good times.

cut forward to later today, and here comes code 63, my TPS voltage was all the sudden too low, and it wouldn't idle correctly. (This TPS is brand new)

Ok, turn throttle screw in a small amount, boom, now idles high, and IAC very much struggles to respond properly. There is no in between. (IAC doesn't respond properly for the "too low" either)

It is now to where if its running and I plug in the IAC, boom, engine starts zooming. I've decided to bring the throttle screw in to where I can keep it running reliably without the IAC, because with it plugged in, the truck is terrible to drive.

All these issues go away when I unplug the new/fully functional IAC, leading me to the topic of this thread, I don't think the computer is properly controlling the idle like it should, it becomes nigh on undrivable with it. I'm thinking it's time to pull the PCM.

Does anyone know who I should send it to for it to get fixed? What do I do with the calibration code?

​​​​​​ Assuming mine has a capacitor or something that bit the dust. If it doesn't I'm completely lost. Please help
​​​​​​ ​​​​​​

 

I tried to remove the computer, but I couldn't figure out how to get it out, so I panicked and plugged it back in, idk if it need to relearn now, but its not running very well and it's kinda freaking me out.


Please, I need help

 

It is removed from inside the cab. Remove the sill plate and the kick panel to get access to the computer. There is a plastic bracket with a 10mm bolt holding it in.

 

Gotcha, I only got the connector off, if I cannot fix these issues any other way, PCM is on the chopping block. I've got it running ok now (not perfect, but ok) so I can use the truck. When I have time, I'll take another crack at it. Electronics are not my strong suit.

Thanks again.

 

Good news, turns out I was missing a small bushing on the TPS, and the throttle shaft "slipped" off a bit. And I still happened to have it, they don't give you a new one with a new TPS. This was able to get my truck running ok (including IAC)

Edit, truck was able to relearn pretty well, world of difference.

https://photos.app.goo.gl/M9Cn6U4


This little sucker keeps the TPS centered over the throttle shaft. Luckily I didn't throw away the TPS I took off.

 

On my 94 F-150 the cpu came out the front. Remove the Plastic inter fender, Turn the wheel left and you will have good access. You can remove the wheel if you want to. Yours may be different being it's a few years older. Note: My cpu got water in it from above thru the wireing harness, so I made a sheet metal roof over hang with a lip and drain point. Also installed a piece of foam seal on the top edge of the firewall to hood gap to help stop the water running down on the harness. Another note while your down there, clean out the clogged up drain hole from the valise up top. If it cloggs the the valise will rust through.

 

I will definitely create some sort of cover for my connector now that you mention it. Luckily for now, putting that little bushing back on the TPS made things WAY better, and I probably don't need to pull the PCM.

 

That is correct for a ‘94 but not for a ‘91.