warren70

Hello everyone o/
I've been searching but have only found answers to problems similar to mine, I'm hoping someone might narrow this down for me.
I have 94 with a straight 6 300.
No matter what the temperature, or time of day, every time I start my truck the RPMs race up to what sounds like full throttle for a couple of seconds, & then settles to normal operation. It runs fine, no surging, but every now & then, It will choke & die, but only when I pull up & put it in reverse.
The revving of the rpms started a few months ago, was a once in awhile thing but has progressed to every time I start it. The choke & die, that's been going on since I owned the truck, for the last few years.

I was gonna replace the TPS & IAC, but would like to see if it may be something else altogether.
Thanks for taking the time to read, & for any advise/solutions o/

justintendo

likely the IAC is dirty or needs replaced

fltdriver

Start by pulling your codes, whether or not your CEL is on you should still have codes.

You can test both the TPS and IAC:
TPS: .9-.97v closed throttle, 5v WOT, smooth increase as you move the throttle lever.
IAC: 7-13ohms between vehicle power pin and IAC connector pin.

Any other reading and they need replaced, TPS is a motorcraft ONLY part.

Never hurts to clean your ThrottleBody blades (edges of blades and TB where the blades rest are the most important), use TB cleaner and a toothbrush/rag.

TPS doesn't sound like the problem, doubt IAC is either. Sounds like you may have an issue with your (forget the name right now) ?gear selection sensor? (whatever it's called). One of these: PNP-if auto, CPP or MLP if manual. Your codes should point you in the right direction.

How to pull codes:
https://www.f150forum.com/f10/how-re...es-obdi-10907/

What they mean:
http://www.troublecodes.net/ford/

warren70

Ok, well, I was able to pull the codes, now Im no stranger to counting flashing lights on a dash, but this seemed like it could have been read 2 different ways. I did this 4 times just to make sure I got it.

65
46
54
-----long pause
1
-----long pause
51
25
12

OR!<<<<<<<<<<<<<<<<<<

654
654
-----long pause
1
-----long pause
512
512

Neither seem to make sense to me, or I have the wrong code definitions.

fltdriver

The second set is correct, one thing to remember is that codes are always given in numerical order (lowest number>highest number).

654-selector not in park.

Like I said the selector sensor, still can't remember exactly what it's called, hopefully someone will chime in.

512-memory power (pin 1)

Need to pull the connector to the pcm and clean it up really good, quick drying electronic clean and a brush. As long as you're doing that get as many connectors in the engine bay as you can, use a paint pen or sharpee to mark them so you know which one have been done. Cleaning connectors and grounds/terminals goes a long way in preventing most electrical problems that these trucks have.

warren70

Yep those are the same code definitions I got. I shall get with it this weekend when I get back home then. Maybe by then we will find the name of this selector Thanks for help, & I'll update any progress, or any other questions as I get into it.

dRem

I had a similar problem in my '87. A new IAC valve helped, but didn't solve it entirely. It turned out the gasket between the upper and lower intake manifold had a break in it, so that vacuum leak was the main cause. The rest of the rubber vacuum hoses attached to the top of the intake manifold needed fixing/replacing.

Basically, check for vacuum leaks.

warren70

Yep, did that this past spring, they were all dry rotted.

warren70

Would it be the "throttle valve controller" at the transmission?