Like the title says, I have a 1993 F-250 with the E40D transmission and a 7.3 idi non-turbo.

The overdrive light is flashing and it only has problems when overdrive is engaged and I am climbing a hill (not towing). When climbing a hill w/ overdrive engaged it will start jumping between two gears (possibly neutral). The tachometer jumps between idle and 2200 rpm.

I already tried adjusting the tps. It was down around 0.71 volts (idle), and now it is 1.20v at idle, and 3.85v with the throttle all the way open. I also tried it at 1.35v idle with 4.06v fully open.

Any thoughts would be greatly appreciated.

Thanks

 

Bad tach sensor ...

-Enjoy
fh : )_~

 

My thought would be to read the codes before wasting money throwing random parts at it.

Ford ? OBD Trouble Codes

 

I agree when you don't know the issue ... Bouncy Tach says it all!

-Enjoy
fh : )_~

 

I tried reading the OBDI port with a code reader (I work at a parts store, so I have access to one) and it would not read the codes. And none of the shops around me will read codes. So hopefully I can get the codes to read using the method posted.

I will try the tach sensor if that does not work, but I just want to make sure I was clear when I described the problem. The tach only bounces when I am having the issue, and the engine is clearly changing RPMs when it happens.

Thanks again.

 

Yup, that is because the Tach sensor is failing causing the transmission to freak out.

Tach sensors have become spendy, if money is tight and you are near a Salvage yard, check em out, if the wires going into the sensor at the sensor are solid without cracks they are most likely still good ... Not a guarantee, but a decent bet!

Typically the wires crack allowing moister into the sensor causing it to fail.

-Enjoy
fh : )_~

 

& Check the FAQ, there are a couple of links to some different DIY ideas on making your own tach sensor for very little.

 

https://www.ford-trucks.com/forums/1...l#post13750581

https://www.ford-trucks.com/forums/1...l#post14500073

 

Ok, I will order the sensor when I get to work today. Something I noticed late last night is that the cable connecting the pedal to the throttle does not have any tension on it, and the engine is idling amount 450 rpm instead of he 675 rpm on the valve cover. Assuming that is not related to the tach sensor, could that be giving me some of the problem I am seeing? It would mean that the tps is not set correctly.

Thanks

 

The throttle cable should have slack at idle, if not it would hold the throttle open.

The TPS is connected to the linkage, not cable, thus the cable has nothing to do with the setting of it ... Unless the cable is to tight and holding the throttle open.

The idle screw is on the right side of the IP, towards the front and it angles at about 45 degrees towards the front of the truck, they typically have both a Screwdriver slot as well as a hex head.

You must set your idle before setting the TPS.

Do not adjust the one that is further to the rear of the IP on the right side, vertical and without a hex head.

-Enjoy
fh : )_~

 

The tach sensor finally came in this morning and I got installed. Looks like everything is working now! No flashing OD light no bouncy tach, and no weird shifting. The only issue now is it sometimes revs for 1/4 to 1/2 a second when shifting. oi guess the best thing to try on that is getting the idle to the correct speed and then adjust the TPS.

Thanks for your help and patience!