I recently removed my intake plenum and cleaned it up really well. (You would not believe the amount of deposits that were in there) and I went ahead and shined it up to. While I was doing this a friend cleaned up my throttle body. When I handed him the throttle body I did not bother to take off the TPS or the IAC and he sprayed them both with brake cleaner and I did not realize it until it was to late.

Now.. Two questions..

I am now getting a TPS code from my ECM that I never got before. Should it just be replaced or is it something else? ...and is it recommended that I replace the IAC at the same time?

Also... Please look at this picture:



Before I shined up my plenum and replaced my TPS wiring harness I noticed there was a wire spliced into the black wire on the harness that lead to the intake plenum. (just sits under a bolt for ground?) When I replaced that harness I did not bother putting that splice back and the car ran like crap!

Anyway, I spliced a new wire (with a wire-tap) and connected the bright red wire you see in that picture under a bolt on the intake plenum and everything ran smooth once again. Like there was never a problem.

Is this a sign that that particular bundle of wires (that includes alternator, IAC, TPS) is bad? The reason I ask is because I am having some power issues with alternators going out, and only working half-@$$ed. Could this bundle of wiring be that problem as well?

If so what is that bundle of wires called, and what is the suggested route of replacement? I know where they end, but where do they begin?

 

Weird; nothing like that should be there (the wire going to the plenum). It comes from a black wire in the alternator/tps/iac bundle?

You could try resetting the TPS ...

 

Hm, bleh. The last time I got a tps wet, it lasted two weeks and then started jumping radomly all over the place. I would get a meter and check it, or if you have one of them scanners where you can watch the values in real time coming from the sensors to the ECU. You can watch it there and see if it spikes or jumps around when moving the throttle blade. Should sit around .55vdc +-0.05 at idle from what I understand.

-Dan

 

You guys think that after I replace the TPS today I should remove that wire and see how things run without it again? Maybe it is a TPS issue and not a wiring issue?

 

Did you disconnect the battery before unplugging everything- or possibly turned on the key while things were unhooked (maybe listening to the radio?) Codes are stored and just may need to be cleared from when you unhooked things.

 

As far as the whole "should I leave the wire there or not issue", that really depends on what the function of that wire is, which will then indicate what the real problem is.

 

That wire acts as a ground currently, and as per the battery... I disconnect it when I do anything and everything. Screw radio presets.

I am putting in a new TPS, IAC, and EGR this weekend. It should be interesting to see if I notice any change in the way the car runs.

 

Yes, I realize that it is a ground, but what does that wire connect to? Is it the TPS ground? some sensor ground? We may be able to track it down, with a little more detail.

 

In the original post I said where it starts and ends. For clarity though allow me to say it again...

On the TPS wiring harness it is spliced into the black (top-most) wire with a wire tap and the other end leads to under a bolt on the intake plenum. I ran the car without it and when I would hit the gas the car would studder a lot before it rev'd or it would just die if I did not punch the gas soon enough. Replace that wire and it is steady again.

So I kept the wire, even though I am uncomfortable with mickey mousing anything in my car, let alone such an important part of the system.

Thanks for the responses.

 

Ok, so it IS the TPS ground wire that you tapped into?, it sounded like you were unsure of what wire it was.

That wire should also ground a few other sensors, and may be more of a cause of the rough running than just the TPS, but one thing does kinda make me wonder, I'm not sure about the code that is used in 3rdgen F-bodies, but I know with most others, if the ground is bad or missing from the TPS, the car generally won't start, since the ECM sees this as a "clear flood" situation. This gave me greif when I swapped The Franken60 (my 3.2L turbo) into my Jimmy, some how I missed hooking up the TPS ground and it would not start.....

Have you checked the grounds that attach at the rear of the head, to the tranny (IIRC) and anywhere else the grounds are attached or supposed to attach? It could be something as simple as a loose bolt, or a missing/rotten ground, or corrosion.

As far as the replacment question on the TPS, have you checked the resistance of it through the full range of throttle movement? Checking voltage with the key on, engine off, can also determine what may be going on and can indicate if the sensor is bad or good. Myself, I'd start with finding the wiring issue, and then move on from there.

 

Great advice..

Thanks!

 

For more clarity I have included this close-up picture so you can see exactly what is going on with my TPS.



You can see here that it is going from the top-most black wire on the TPS wiring harness to the intake plenum.

Any new thoughts?

 

The f-bodies will go into clear flood mode at WOT, when TPS is at max voltage- not sure how that is read if the ground wire is disconnected. That wire definately shouldn't be there- it's someone's fix. I would also wonder as to the quality of the ground; it's going thru the intake, which is aluminum, and only joined to the engine block by bolts, because of all the gaskets. I don't have my manual handy; if I think of it, I'll look up what that upper wire is for when I get home. I assume it travels into the wire loom that's on the passenger side's main frame rail, where several ground wires (including the MAF) come to a single ground wire, and then that single wire goes to the back of the passenger side head. The junction should be covered in tape, and be close to the heater/evaporator box's bottom.

 

That would be great if you could check the manual for me. Thanks a lot.

 

Without a ground to the TPS, the TPS voltage will read WOT, or about 4.9V, at least that is where mine was when I somehow missed teh TPS ground when I did my conversion, my truck was originally carb, so I had to wire everything.

With a poor ground it may pull down the voltage enough so that the ECM thinks that your throttle is open moer than it actually is, but not quite WOT, so it will still start and run, just poorly, since it will usually be extending the injector PW, and advancing the spark timing, depedning on the PROM tuning and other variables.