So, I am coming back from lunch and my transmission won't shift out of 2nd or third. I turn off O/D and it felt like the TC locked but no O/D. 2800+ RPM at 45 MPH. I think, well maybe gear selector is not engaging drive. I stop at a light, put it in park and back into drive, continue driving but no change. Still won't shift. I figure it must be some computer glitch, so I stop at the next light and put the truck in park, shut it all the way off, start it and continue driving. This time I get all my gears and O/D works.

No, the O/D light did not flash.

Any ideas what this means? Problem with operator or transmission? I'll report back when/if I get home later this afternoon. I have never had this happen in the truck before.

1991 F250 7.3 IDI all stock.

 

I'll check the fluid level before I leave work.

 

Good idea. LOL
Could be the MLPS switch took a dump on you.

 

first thing you want to do is scan for codes.

 

Says no O/D light flashing. will there still be codes?

 

92 and up will flash if a code is stored. 91 and older will not.

 

Thanks. i learn something new everyday.

 

I checked the fluid before leaving work tomorrow and it was in the hash marks. It hasn't done it since, so that is good. I will take it down to O'reilly's and have them scan it for codes. It is OBD-1 right?

 

Yes. OBD2 started in '96 i think.

 

OK. The two messages the guy at O'Reilly's saw was a MAP sensor pressure fault and the TPS. The TPS may be because my throttle cable is messed up. I'll have to figure out what a MAP sensor does.

Edit: At the time, I thought a MAP sensor if for a computerized gasser. It is starting to look that way to me.

 

I wonder if his reader is messed up.... You shouldn't even have a MAP sensor...The TPS helps control the shift points. It could be out of adjustment...

 

Eaton I can tell you from your description that it was your TPS that was causing it. I can tell you this cause my 94 just did the same thing. Check the voltage on your TPS with a meter with the key on and engine off. Bottom wire should have 5 volts, top wire should have no volts, center wire should reat somewhere between 1 and 1.2 volts with the throttle at idle and should go up to between 4 and 4.5 volts when you push the throttle level to wide open. I couldn't get my TPS to adjust to with in range so I put a new one on it day before yesterday and problem solved and no more code 23 on the reader!

 

Yeah, I adjusted it when I put the old pump on. It is at 1.08-4.28 if I recall correctly.

 

Check for a smooth transition between idle setting and WOT. Anything that causes a dead spot, or spike in the reading could confuse the computer enough to cause problems.

 

Also you may want to go back and check it again. I got mine set and kept getting the code 23 on the reader, went back and checked it again and the voltage had changed. I never could get the voltage to stay at what I set it at so I put a new one on it and problem solved.