94.5 idles but no throttle

[twin_turbo]

I have a 94.5 f350 that we swapped a 7.3 into. we have it running now but it wont accelerate and will only idle. the motor is a 94.5 the wiring is from a 95, underdash harness 97, pcm 95. There are two codes: po122 and p1661 which are low voltage input at tps switch

So far we have tried a new computer, swapped pedals and the one I have works, relays, and I have pulled the wire loom off and have checked all the wiring under the dash and hood that is in the same circut as the accelerator position sensor. There is power to the brown and white wire that ties into all of the sensors, computer and aps and there is power to all except tps and barometric pressure sensor. I tried to connect the aps and baro sensor to the plug outside the cab and they have power but still no luck.

I am starting to get frustrated and I am only down to a few possibilites that I think are causing it. 1) the 97 harness will not work and i will need to get a 94.5(everything works except throttle, windshield wipers and cluster which is gas ) 2) There is a broken or shorted out wire in the cab but I can't find it after 4hrs of searching all wiring looks good. 3) keyless entry box- has plugs in harness but I dont have one to try and doubting this is the problem. 4) idm or a sensor?
I have talked to the diesel mechanic at ford and he figured it would be the tps or ivs. If I cant figure it out in the next day or two I am going to take it in and have them put it on their computer. thanks for any info

 

[Arisley]

Moved to the appropriate place.

 

[twin_turbo]

moved

thanks for the moving this. I was just checking for any replies and saw I posted it in the wrong category.

 

[SPEEDDEMON31176]

Based on your description, I would venture a guess that you have a harness conflict. You will need the schematics for both the 97 and the 94.5 and see if there is a wiring mismatch somewhere.

 

[twin_turbo]

I am thinking that I need the 94.5 underdash harness. let me know if you know where I can get one. thanks

 

[Stacks92]

What year is the tps from? Cross reference the colors of the wire harness to the tps. I think that on a 95 they are different from a 97 ect... My guess would be that perhaps they switched the power wires around in the plug in for the tps so instead of your supply (power) wire going to the tps it could be the ground thus causing low voltage signal back to the tps.

 

[Patrick Feeley]

I harp on this all the time: If you're going to keep your truck (or do a bunch of work such as this), buy the Electrical and Vacuum Troubleshooting Manuals (EVTM)!!!!! Best money you will ever spend!

Just looking at the diagrams (I have all the EVTMs from 94 through 97) here is a description of differences between them (NOTE: only the TPS described below!):

1994:
Reference Out Voltage is on circuit 351 (BR/W). This wire is from connector to PCM pin 90 (and also goes to the BARO, MAP, CPS, EBP, and ICP).

Sensor Signal Return is on circuit 359 (GY/R). This wire is from connector to PCM pin 91 (and also goes to BARO, MAP, IAT, EOT, EBP, ICP, and pin 2 on the IDM).

The TPS "tap" is on circuit 355 (GY/W). This wire is from connector to PCM pin 89.

1997:
Reference Out Voltage is on circuit 351 (BR/W). This wire is from connector to PCM pin 90 (and also goes to the BARO, MAP, CPS, EBP, and ICP). (so really no difference there)

Sensor Signal Return is on circuit 359 (GY/R). This wire is from PCM pin 91 to all of the following: BARO, MAP, IAT, EOT, EBP, ICP, and pin 2 on the IDM. It does not go to the TPS! The circuit 570 (BK/W) wire on the 97 TPS connector needs to get spliced into the circuit 359 (GY/R) wire for the sensors listed above in this paragraph to be consistent with 95 PCM wiring). On a 97, circuit 570 (BK/W, a ground) wire would go to PCM pin 24 (that pin is not used on earlier trucks).

The TPS "tap" is on circuit 355 (GY/W). This wire is from connector to PCM pin 89. (so really no difference there)

Now as far as other differences, there looks to be some other differences at C202 (big harness firewall feedthrough connector). Probably not a lot of help. Cheers!

 

[twin_turbo]

I have the book for a 96 but need to get the 94. I will try to splice that wire and I am going to try to find a 94.5 underdash harness so everything matches. thanks for your help. ps. if you know anyone who has one or where i can get one let me know!

 

[Patrick Feeley]

If you have a 1995 EVTM, you should be good should you ever switch to a 94 underdash harness. The only real difference should be that the 95 EVTM will show the differences specific to an E4OD truck and those for a manual tranny as well. Also, make sure that the circuit 570 (BK/W) just goes from the TPS connector to the circuit 359 (GY/R) wiring. Cheers!

 

[twin_turbo]

I tried splicing the wires with no luck. I am still looking for an under dash harness but other than that I don't know what else it could be? Thanks for your help

 

[Estrogen Hostage]

It's in the throttle pedal wiring. I'd start probing both ends with a multimeter and try to find a problem.

What kind of wheels are those?

 

[twin_turbo]

Wheels

The wheels are stock off of my 08 f350. I had adapters made by motorsport tech. Thanks for the reply, i am still trying to find an underdash harness. Hopefully that id the problem. Let me know if you know where i could get one

 

[Estrogen Hostage]

Sorry, I don't have a dash harness. My parts truck is a gasser.

What tire size is on those?

 

[twin_turbo]

tire size

I am pretty sure they are 245/75/17. they are the stock continental tires

 

[twin_turbo]

Throttle Fixed

Finally got the obs running. I ended up getting a 97 fusebox and underhood wiring. Switched that out and it solved the no throttle issue! Took it for a road cruise and blew the icp sensor out of the head after 2 miles (cheap replacement i got off ebay). put a new pigtail and icp sensor(oem) on and that solved that problem. just need to swap out the hpop and finish the paint and its ready to hit the road!