legacycentral bbs

Ok, so i picked up Derek's old project car, because it helped him out and I figured we could get it back on the road.

The reason this is a murder mystery, is if we can't solve the issue, the car becomes a parts car.

So backgroud info: Derek has a mint 91 SS 5-spd, 100K miles. Lady T-bones him. He picks up a 93 SS auto with 220K and tries to swap engines and transmissions. The plugs are different from 91-93, so he works around it and gets the engine in. He starts it up, and the car idles at 2k, and smokes bad. ( we figured out the smoke issues later after I got it.) But he gets frustrated and puts the original engine back into the 93. He starts it up, and again, the 2k idle. We pick up the car and get to fixing a few issues. His changeover from the auto to manual was completed, and we checked the TPS. It is reading either barely idleing or full open throttle. None of the middle positions are registering. We tried another TPS, with the same issues. We are thinking that in the swap, something happened to the TPS wires to the ECU and they were crushed/broken or something. But we have not ruled out other options.

I just would like to hear of another reason why the car will not idle.
( Oh, and we can't find any codes; or that it appears to not be throwing any)

Thanks

Have you verified continuity from the TPS wires to the ECU?

When you say you check the TPS and it's not registering the middle positions, is this at the TPS plug or at the ECU?

Could it be as simple as two bad TPS's?

My guess is that the idle issue is related to the TPS signal if everything else is good - you did clean out the IAC correct?

My questions are pretty basic and you've likely already addressed them but those would be my first guesses.

I agree it's likely a wiring or IAC issue, but what about swapping ECUs?

It's not posting codes so I'd suspect hoses myself. Simpler to check too.

I thought about swapping the ECU,s but have not gotten there yet. Since ther ECU will not read anything but the extremes, I thought it was a computer (ecu) or TPS or wiring issue.

OK, she still has a TPS sensor code, and we are tired of trying to find the issue, and can't get an answer.

SO- that being said, I am sending out a last minute- help me if you can- if not I am going to part her out.

Unless you have the answer to my problem:
ECU sends out just a TPS sensor code.
Tried 4 different sensors: nothing
tried bypassing the stock wiring with new stuff from the ECU to the sensor: nothing.

Tried 3 different ECUs: nothing

replaced IAC valve: nothing.

At the end of the rope........

Being that you tried wiring it from scratch, the following probably doesn't help, but I felt like throwing something out there. OK, I hate automatics so the 4EAT might use something different, but does it use a kick down relay when floored? Perhaps there's some way this signal gets sent to the ECU and interpreted as WOT. The closed throttle signal could come from the IAC. That leaves the TPS as possibly not hooked up at all rather than being really f'n strange. OR there's some sort of other residual automatic wiring crap causing the interference. Occam's Razor and all that—essentially, the only thing that's changed (not just been replaced) is the transmission.

We did the correct procedure to change from manual to automatic( cut those few wires from the ECU,ground one, etc etc and remove the autotranny computer. )

According to Subaru, all of the 91-94 turbo cars use the same ECU ( auto and manual) The only difference being a few wires and the signals to the tranny computer.

I guess the problem lies in that we can't think of where else to go......

TPS code. replace tps: nothing, check wiring good, bypass stock wiring: nothing, change out ECU: still a problem.

Unless someone has another idea WHY the tps code is still popping up, this car is going to be a organ donor.

I had a high idle problem and it was because the harness that attaches to the IAC was loose. I know you completely replaced the IAC, but maybe you should trying running some new wires to the IAC, just as you did with the TPS.

It might sound like a little too much extra work, but the problem is EXACTLY what I had, even the TPS code, but it was actually the wires to the IAC.

asc_up wrote:I had a high idle problem and it was because the harness that attaches to the IAC was loose. I know you completely replaced the IAC, but maybe you should trying running some new wires to the IAC, just as you did with the TPS.

It might sound like a little too much extra work, but the problem is EXACTLY what I had, even the TPS code, but it was actually the wires to the IAC.

I will try that.
Then my only other option is to work backwards on the MT to AT conversion electrically.

Then it gets parted out.

2 suggestions I'll offer up -

1. Have you tried running the car in D-check mode? If so, does the scenario remain the same?

2. Have you hooked up a scan tool to the ECU to verify the signals that it's receiving? The TPS is just a silly little 5V sensor that goes down to just about 0V with the pedal to the floor. If you observe the readings in the ECU, and verify it's operating within the proper range - you're not getting the code because it's wired wrong.

Just my 2 cents.

well drew i have not clue, but i will take the car off your hands.

I didn't see you say this and I know it's a stupid question but did it have this problem before the swap?

Because when I swapped mine into my 93 Impreza it did this till I drove it and it seemed to fix the issue. Mine didn't throw any codes either.

Does your TB have bypass air screw on the top of it?

http://main.experiencetherave.com/subaru/images/TB/

Also, if you can find or use a scan tool, look at the ECU parameters for the TPS and IAC valve.

Drew, if you need one, I'd be willing to ship my Revscan cable to you and you can just download Revscan for free from Revtronix.com. It will display the TPS and IAC valve signals. Just let me know!

The car has been sitting at PIA for over a year now. Jake and Steve are pretty much ready to give up on it. ( Steve says he has rarely been stumped in over 15 years as a subaru master mechanic, but the car has him stumped.)

They have a ECU scanner on it, and it keeps giving JUST the TPS code. It idles ok now. According to Derek, he bought the car and it had no problems. But after he tried the swap, is when things did not go right and it was not idling and had the TPS code.
( that is why I have it)

So they are ready to put some C4 in it and do a myth busters, but I have a subaru AWIC, 4 pot/2 pot setup and a few other parts ready to go in it.
BUT IF IT CAN"T RUN, I CAN"T DO A F'N THING WITH IT.

So that is where I am at.
( PS- shoot Jake15 a pm to help me say thanks for working on it even though we have not achieved anything.)

Lets not give up on it just yet. You say it idles okay now. Does it run properly also?
It sounds like it comes down to a communication problem between the TPS and the ECU. Can you check specific sensor outputs w/ the scanner? If so, does the TPS act appropriately? Have we checked that the TPS connector is wired correctly, i.e. the pins @ the TPS connector have continuity w/ the proper pins @ the ECU connector?
I know it sounds silly, but we can't rule out or overlook the simple stuff. I know Steve and have seen the car sitting there @ PIA for a while, but sometimes its easy to assume and overlook the simplest of problems.