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What exactly are the tell-tale signs of a bad TPS sensor. If I get on it hard, say on the interstate, it won't shift up into overdrive until its practically maxed out in RPM's. If I'm right and this is what I might need to look into replacing, where do you get them?
Usually it starts dropping out of OD and then back into it randomly or won't shift at all. If it just waits to shift, adjust the nut that is on the output shaft just below the TPS sensor. Turn it counter clockwise a little and see if that helps. If that made it worse, go back the other way past your initial setpoint. (as you can tell, I can't remember which way to turn it!) I think it is a 10MM wrench. Don't be afraid to try this, can't hurt anything. Just make a mark where you start from so you can go back if needed.
You just reminded me of something I was going to do. I took the sensor off my truck and replaced it with a pot mounted in a small box on the dash. I can change the set point from inside the truck and the TPS problems went away with the sensor! :thumbsup I was going to dig out the instructions and post them for anyone that wanted to try it.
93 D250, PDR Twins HX35&HT3B, 60+# boost,PDR stage 2 head w/o-rings, PDR Cam, modified VE Pump, piston style lift pump, modified 5" intake w/AFE, ATS ported manifold,DTT 89% converter, 4" RIP exhaust, modified tranny, EGT/boost/tranny/tach gauges, TPS removed, a little chrome under the hood. Mag-Hitec tranny and diff. covers. Rear sway bar. Line-x bed liner, after market seats. Single stage Water/Meth system installed. Oversized intercooler w/3" IC lines.
sweet thanks alot paccool, I'll have to try that. Its a little annoying, considering its the only reason i lost the race to my brother. I had him all the way through the gears (he has a standard, mine auto) until i stopped accelerating while still in 3rd. He passed me and I bore the look of shame. Not for long, as his only tops out at 78 or so!
u do have one dont listen to him, and i believe its supposed to be around .3 and .9 volts but i'm not 100% sure.
and for cumnspwr, don't start saying stuff if you don't know anything about what your saying... i need to adjust mine now too, it shifts in and out of overdrive and is kinda scary when i'm drivin down the interstate at like 70-75 and it downshifts... i just don't wanna blow the original tranny with 250k on it...
Pedal at rest, remove the tps BRACKET from the AFC housing, with the TPS mounted to the bracket.
Verify that the hex on the TPS directly lines up with the hex on the throttle shaft by attempting to put the bracket back on WITHOUT RECLOCKING to get it to seat back down.
If you have to turn the bracket to get it to engage, you need to adjust the screw on the TPS until it sits down and lines up the bracket's bolt holes on the AFC housing, with no re-aligning.
Keep in mind, when you guys adjust the pumps and drop the idle screw clear back, as well as adjust the throttle linkage for full travel, the TPS NEEDS READJUSTED!
This also goes for any time you remove the nut on the throttle shaft during a spring change, or other maintenance that requires the throttle lever nut to be removed.
Last edited by Mark Nixon; 09-08-2010 at 12:46 PM.
The Following 2 Users Say Thank You to Mark Nixon For This Useful Post:
The 12 valve cummins does not have a TPS. These started at 98.5 with the 24 valve.
Nice 1st post.
This IS the 1st gen forum board. Not sure why 2nd gen and later stuff is being discussed. None of it's applicable.
The 1st gen trucks (12v) running an automatic transmission indeed do have a Throttle Position Sensor (TPS) that is located on the top of the VE injection pump. It, combined with the PCM (reading other sensors), alters the Over-Drive shift-points.
Original owner of a plain'ol VE fueled '93 W250 ClubCab. Green
This fix might not be for everyone but it worked for me when I was having TPS problems. I used a sharp knife and delicately scraped away the glue that holds the plastic plate onto the top of the TPS itself. Once the glue was removed I was able to again, delicately, pry that plastic cap off of the TPS and clean the inside of the mechanism out with electrical contact cleaner. I re-assmebled everything and used RTV to seal the cap onto the TPS, re-adjusted the voltage, and everything has functioned perfectly since.
1992 W250 I/C, 170,000 miles. A518 auto recently rebuilt. Engine is bone stock. Skyjacker leveling kit, Toyo M55 Tires, all kinds of parts to freshen her up, but she's still just a work horse.
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