I need some help!! (TPS pains)

[Marck]

My subaru has been at the mechanic for about a month now. We are trying to figure out a problem with the throttle position sensor (TPS). I gave him the car to readjust the throttle valve (that my darn neighbor messed with) and the TPS. I know the FSM says to never adjust the throttle valve screw, but too late for that now. Adjusting the throttle valve will also throw off the TPS, so they both have to be adjusted.

 

Here is some history: My subaru is a 1987 GL 3 door coupe EA82T. I swaped intakes from original to a spider intake man from a XT Turbo. The connectors on the intake wiring harness were the same as the connectors to the car by the battery. So I assumed I didn't need to rewire anything. Fuel injectors along with many sensors are the same. The exception is the TPS. The one from the spider is a 4 pin one like what came on the SPFI while the one on my original manifold is of the standard 3 pin (MPFI Turbo) type. Now the throttle sensor is causing the car to have its idle jump around and it also may be the new reason it is failing smog. The mechanic found that the TPS from the spider is not always working properly with my computer. I had him swap on the TPS from the old man and now the TPS is working (better) but the computer is not reading it right or something. The computer is not spitting out any codes. My mechanic has checked all wiring going from TPS to computer. He has been really frustrated with it as well as myself. I want my baby back so that I can drive it again. My mechanic has a guy in LA who is sending him a used computer and TPS to swap into the sube to see if anything changes. I don't think my computer is busted?

 

Anyway I think he said the problem is that the TPS is not telling the computer when the throttle valve is closed. He tried readjusting the throttle valve and TPS many times and he still can't get the darn thing figured out. I even gave him my old intake man and all 5 of my FSM to help him out. He has gone through schematics and found everthing is wired correctly.

 

I am at a total loss. What do you think the problem is? What should I tell the mechanic to check next?

[Marck]

Wow, no replies yet. I think I stumped all board members on this one. No one had similar problems with their TPS? Bump.

[BoostedBalls]

Simple solution???

 

Make adaptor plate to mount original throttlebody on spider intake. That's what I was going to do but decided to go with a GM throttlebody with IAC valve hooked up to megasquirt.

 

Wow, no replies yet. I think I stumped all board members on this one. No one had similar problems with their TPS? Bump.

[Marck]

Simple solution???

 

Make adaptor plate to mount original throttlebody on spider intake. That's what I was going to do but decided to go with a GM throttlebody with IAC valve hooked up to megasquirt.

 

I don't think you understand my question. The original TPS from my original manifold is on the spider right now. It fits perfect on the spider without the need of any adapter plates. My problem is pure electrical. I believe the TPS is working fine now that the original is in, but the computer will not read the signal from the TPS correctly. And yes the TPS and throttle valve have been adjusted correctly by my mechanic.

[idosubaru]

if it helps at all the FSM testing procedures and values for the TPS of an XT6 are not right. no TPS on an XT6 will be within the specifications of the FSM. i'd expect similar results from late model 87 and up XT's. but that's just a guess.

 

i had a troubling TPS issue once. car had trouble idling and wouldn't start on occassion. replaced the connector to the TPS along with about 6 - 8 inches of wiring behind it and all was well. i located the problem by grabbing the wiring harness connector that plugs into the TPS. i wiggled it, then gradually drifter back bending/ squeezing and rolling the wiring between my fingers. about 3 or 4 inches behind the TPS the car would do all sorts of craziness, stall, run right (for once), RPM's jump, not start, etc. replaced the wiring and all was well.

 

at this point i think i'd swap in another TPS and see if that helped. and the ECU like you mentoined he's going to be doing.

good luck.

[Subi81]

I seem to recall that in order to use the spider intake you have to flip the full throttle wire and the idle wire.

 

So as your car stands now when it is idleing the computer thinks "Oh full throttle" When you floor it, computer thinks "I am idleing"

 

Might want to search for it.

 

Good luck

[Marck]

I seem to recall that in order to use the spider intake you have to flip the full throttle wire and the idle wire.

 

So as your car stands now when it is idleing the computer thinks "Oh full throttle" When you floor it, computer thinks "I am idleing"

 

Might want to search for it.

 

Good luck

 

Are you serious? I tried searching and couldn't find it. Can somebody confirm this or post the link. There is no way for me to check this out because my mechanic has my old intake manifold and my car w/ spider. If somebody can confirm that two of the wires needs to be swapped, then I would be most grateful.

[Subaru Jim Maple Ridge]

I just went through the TPS nightmare on an '87 EA82T. I ended up changing the plugs on the harness to a single 4 pin to use the newer TPS. I used the TPS from a spider XT so no, the wiring should not need to be changed. Two circuits, one for the idle switch, and the other to sense throttle position. Look to the manual for troubleshooting procedure.