I have a 1993 Dodge W150 that had the MPFI 5.9 magnum. That motor went out. Put in a 2001 5.9 (used the intake, wiring, etc. from the 93'). Motor is in and here is my issue:

It does not want to stay idleing, it lopes erratically like i have a severe vaccum leak. Give it gas (rev it) and it runs like a dream. Back to idle and it lopes and eventually dies. Initially i thought vaccum leak, but tested and retested and 99.9% positive there is not a vaccum leak anywhere. Had a code 24 (TPS Voltage too low or high). The wiring to the TPS had correct voltage and was all good HOWEVER the TPS SENSOR testing was supposed to be something like 0.5V with TB closed and gradually increasing with the opening of the TB to 3.5V WOT. My TPS showed 5V with the TB closed and 0V WOT. So its basically reading backwards. My questions are---

What would cause the TPS sensor to read backwards?

Could a faulty TPS cause the sympotoms i described?

Is there is a difference between the weights on the 93' and 01' flywheels?

What else may cause the symptoms described?

 

Manual or automatic trans? Did you use the flywheel off the 01? or the 93? Throttle body?

The tps is wrong, if it's telling the PCM that the throttle is wide open when it is closed, things are gonna get weird. The closer you get to half throttle, (where the TPS will actually read somewhat close to what it really should) the engine will run better. As it is, it is prolly running rich as all getout. (might run better with it unplugged......) You could check part numbers, and see if you could use the other TPS you have. (if the other motor came with a t/b that is....) Else, I would replace it.

 

4 speed auto trans A518 (46RH). The flywheel is from the 01', the TB is off the 93' as is the rest of the intake. Is there a difference in the flywheels? I thought about trying the other TPS but it is broken so i'd have to get a new one. Weird how the TPS operated fine before and now it suddenly appears that it went bad....?

 

It's an electrical part. If you so much as look at it wrong, it may become offended, and stop working right......

Somewhere in the late 90's, dodge altered where they put the balance weights, moved from torque converter (earlier) to the flywheel. (later.) If you have the later flywheel, but, the earlier torque converter, you need to address that. Otherwise, you are going to kill that motor pretty quick.

 

I would also suggest ohming out the TPS (with wires disconnected). That would tell you if it is good or bad. Maybe dodge altered the wiring so voltage is backwards. Checking both year wiring diagram would confirm.

 

Thanks for the replies guys, just to update the new TPS solved the issue. Also i got rid of the balance weights on the TC since the new motor had them on the flywheel. Runs like a dream. This is why i joined this website 6 years ago, lots of knowledgeable individuals on here.