Tranny may be in Limp Mode - what do you think?

[jjrock5]

I looked over an AUTOMATIC 91 TSi AWD. The car starts up right away but has idle issues, not that it's related to this issue (or is it?).

The problem is, you place the car in Drive and the car moves but doesn't pick up speed as any turbo car would. It definitely feels like it's starting off in 2nd or 3rd (I believe 3rd is the gear that Limp Mode sets it in from my research). You give it gas and it almost feels like it's a Non Turbo (slow). The acceleration is minimal. It will reach 60 MPH but in an non turbo fashion. The car goes in Reverse just fine and backs the car up beautifully. I didn't get a chance to hook up an analog multimeter to the diagnostic port (which from my research may tell me if there is a tranny problem) Will there be any dummy lights on if there actually is a transimission code stored?

From what I know, the car was stored for the past 4 years in a garage. Supposedly the driver front strut failed before storage so badly that "the front driver corner bumper started kissing the ground" and his fellow "technician" told him that sometimes Auto cars fall into Limp Mode because the tranny feels there's something wrong with the car (in this case the front driver corner was almost kissing the ground) and this is a preventive mode until the car is fixed.

I don't know about you guys but I don't see a suspension issue causing the transmission to go into limp mode because of it. The car is all stock with 120K miles.

So do you consider this to be Limp Mode? Do you suggest any preliminary checks when I go check this car out?

Oh and another point, his "technician" told him that the way you reset the TCU after the issue is fixed is you unplug both battery cables and touch them together for a couple of minutes. Is this even realistic?

The assistance is much apperciated.

 

[jrohner]

1G's are notorious for bad capacitors frying the TCU. I would open up the TCU and look at it or try a different one (they are only the same for 91-92).

You can use a volt meter to try to check for TCU codes, it's the same as checking the ECU for codes except that you use a different wire. There's plenty of info on tuners on how to do this. If there's no signal, the TCU is fried.

 

[jjrock5]

Yea I saw in plymouthlaser.com on how to check for tranny codes. So you're saying only 91-92 are swappable? I can't grab a 93 or 90 TCU and throw it on this car (not that the TCU is definitely the problem)?

 

[GDNF2ET]

Yea I saw in plymouthlaser.com on how to check for tranny codes. So you're saying only 91-92 are swappable? I can't grab a 93 or 90 TCU and throw it on this car (not that the TCU is definitely the problem)?

A 91- early 92 TCUs are three plug ( 3 yellow connectors plug in the side), late 92-94 TCUs are 2 plug..
You can use any three plug TCU to test to see if thats the problem( 1.8, 2.0 NT, fwd turbo, awd turbo)...

 

[rbwtrans]

A 91- early 92 TCUs are three plug ( 3 yellow connectors plug in the side), late 92-94 TCUs are 2 plug..
You can use any three plug TCU to test to see if thats the problem( 1.8, 2.0 NT, fwd turbo, awd turbo)...

You can use any TCU to test, just remember that a non-turbo trans has different gear ratios since it is a different transmission. A non turbo TCU will go into limp in by the time that you get to third gear because it will see "incorrect gear ratio".

 

[GDNF2ET]

You can use any TCU to test, just remember that a non-turbo trans has different gear ratios since it is a different transmission. A non turbo TCU will go into limp in by the time that you get to third gear because it will see "incorrect gear ratio".

I've tried every 1g TCU combination in my AWD, and in my experience, a 1.8 TCU will not put your car in limp mode during normal driving..The shift points are way off and is the worst replacement, but will get you by in a pinch...

 

[slvrbllt]

open up your tcu and check it out
it will usually take it out of limp mode

 

[thiazole]

Maybe the transmission is in limp mode, but I don't feel that the OP has really established that fact. He said the car accelerates sluggishly, and based on that and that alone, he and everyone else jumped on "TCU limp mode". I would at least verify that when it is in 1st gear that the car feels the same and will go 60mph at fairly low rpms like it would if it were in 3rd gear. For all we know, when the "front driver corner was almost kissing the ground" an IC pipe drug on the ground and put a huge hole in it preventing him from being able to build up boost. Does the boost gauge show boost? A TCU wouldn't prevent that. Also, he says that car is always sluggish, even at 60mph, but when my car is in 3rd gear, it is only sluggish at low speeds, not 60mph.

 

[GDNF2ET]

To the original poster, unplug the TCU and then go for a drive..If nothing changed, your in limp mode and thats your main focus...

 

[brian9397gsx]

im sure your in limp mode from your past posts im sure you would be able to tell a boost leak from a trans issue. my friend has the same issue a 91 talon stuck in limp mode with fried tcu. the tcu is unresponsive when trying to pull codes. its doing the exact same thing as yours. unplug it and drive it if its the same open it up and check the caps good luck