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Discussion Starter #1
Car Details:
1991 3000GT SL
67,000 miles
Automatic Transmission
Fluid levels and color look fine

Symptoms: when first started in the morning, the transmission SLAMS into reverse....and I mean it slams. Gets better as it warms up. When I put it in drive, it seems to be stuck in 3rd gear and won't shift at all. If I put the transmission in 1st or 2nd, it gives me third. When I hit the overdrive button, the only thing that happens is the light on the dash goes on and off....

At 40mph, I'm running about 2400 rpms, and at 50 mph it's about 2850 rpms.

The vehicle was driven regularly for the first 10 years (to about 60k miles) and has been driven very little the past 10 years....I'd say about 500 miles a year. Most recently it was parked in the garage for a full year....yeah, I know that isn't good for the car. :( I have driven it about 100 miles (low speeds on side roads) the past week, and no change in the shifting problem....I was thinking the trans may have been gummed up due to lack of use, and would break free, but it's still not shifting, and I'm concerned I may burn it up if I drive it much more. When I get it up to about 50 mph, it feels as though it's stumbling a bit, but that could be due to having old gas in the tank (see above comment about not driving it for a year!).

Any help would be appreciated. Thanks!
 

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It sounds like the trans is in Failsafe mode (3rd gear)
You need to put a scanner on it and retreive the codes . If you can't comunicate with the TCM (Transmission Control Module) then you may have a bad TCM.
 

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I just had this EXACT problem happening with my car this morning.

There was the tell tale of some slam between 2nd and third speed yesterday when I came home.

Reverse and 3rd gear only now...

For the TCM codes, my mechanic told me there was one coming from it but it did not revelead any specific information about what is already obvious: something wrong with the tranny.

I did not have him spend time on it yet, I fear the transmission is a goner. :(

Edit:
Well, I've read other threads and seems pretty much all related.

I'll try changing the oil first and keep old oil to see if it smells bad if the band is burned. From what I've read, if it's dark and smelly, it would the case.

Not sure if this fails that I have the skills to check the TCU manually, I'll follow the discussion in http://www.3si.org/forum/f72/first-third-reverse-502105/index3.html
 

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I just had this EXACT problem happening with my car this morning.

There was the tell tale of some slam between 2nd and third speed yesterday when I came home.

Reverse and 3rd gear only now...

For the TCM codes, my mechanic told me there was one coming from it but it did not revelead any specific information about what is already obvious: something wrong with the tranny.

I did not have him spend time on it yet, I fear the transmission is a goner. :(

Edit:
Well, I've read other threads and seems pretty much all related.

I'll try changing the oil first and keep old oil to see if it smells bad if the band is burned. From what I've read, if it's dark and smelly, it would the case.

Not sure if this fails that I have the skills to check the TCU manually, I'll follow the discussion in http://www.3si.org/forum/f72/first-third-reverse-502105/index3.html
What was the code ? , If the TCM finds anything electricaly wrong, it will trigger a code . If any code is present ,the trans goes into failsafe mode . So, after you get a code, you need to fix it before you determine that the trans is no good. Makes sense ?
 

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Sorry for delay. The modules were not returning any precise code. Seems I had a worst problem than I tought... A coil pack gave up but not before melting the electronic module near it. Which gave up an electrical surge all the way to ignition module... Can't beleive Mitsubishi placed the electronic right near a coil pack...

So you'll ask me what it have to do with the Atx, well that first module pulsations were off as it was melting, there was a electrical power surge and the ignition ECM was badly damaged and this probably also affected the tranny module. The car was still running normally despite two badly damaged modules, it's not until the coil pack gave up that we saw the whole deal.

Or maybe it all happened at once. Who knows. The main problem is that a eletrical power surge definetely happened. I find it odd, should be some safe fail somewhere along the line but does not looks like it...

So far seems I can save the tranny module, the problem did not reappear but I had to change one coil pack , and two ECM for a whooping 2000$ overall... ( And I was actually lucky to find thoses modules ). There is no telling how long the other coil pack still have to live or if the ATX module also was damaged with a new problem waiting to happen.

Anyways, it's ''repaired'' and the car is for sale as is. It's a shame, the engine only have 80k km, had it replaced a while ago. I'm tired to spend money on it. I'm a new dad, and I guess theses times are over... I loved this car more than anything but I must move on... :(
 

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Bringing this thread back from the dead. My car did indeed have a bad TCU, which has since been replaced and it's now running like a champ. It was difficult to find a used TCU for a 1991 SL, had to scour eBay for a while to find one. My TCU was not repairable since one of the 3 main chips had "popped", and there is no source to replace these chips (other than to take one off another TCU).
 

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Bringing this thread back from the dead. My car did indeed have a bad TCU, which has since been replaced and it's now running like a champ. It was difficult to find a used TCU for a 1991 SL, had to scour eBay for a while to find one. My TCU was not repairable since one of the 3 main chips had "popped", and there is no source to replace these chips (other than to take one off another TCU).
This is scary... I have the EXACT same situation with my ES... I removed both the ECU and TCU and sent them out to both be rebuilt... Hopefully when I get them back in a week, everything is fixed... or its "part out" time for me!
 

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Got my ECU and TCU back today... Tranny now shifts better than it ever did before...

They only thing the rebuilder would tell me is the my tcu lost the 5 volt reference. Not sure what that is but I dont care... All I care about is that it shifts again...
 

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Hey newbie! Often people are no longer around to answer a question on a post thats a few years old. You are welcome to start a new one in the new owners section or if its trans related, in this forum. Welcome.

-SP
 

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Hi

i have same symptoms and my rpms are acting crazy sometimes work and sometimes dont. i use my OBDII scanner and first it gave me code P1715 which it was pulse sensor when i change it now it gave me P1750 whitch its a generic code. Most people said its the selenoid kid. Has anybody deal with this issue?
 

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I have the exact symptoms, very hard shift to reverse, seems to be locked in 3rd gear, no check engine light, engine stumbles and occasional backfire to exhaust, also has high idle on startup (1800).

Sent my TCM and ECM to Modular Repair Pro in Van Nuys...spent $250.00 to have both computers repaired. Installed both computers and not much has changed. Have about 10 miles. Not sure if that is enough for the computer to relearn (if that applies to EEC 1 systems) Not sure what to do now....At my wits end on this car. Only has 68,000 original miles, but can not find a qualified mechanic that knows much about these cars in Central California.....any help or advice is appreciated...Willing to pay $50.00 reward to first person to give me the correct advise on this repair.....It is a 1991 SE non turbo 24 valve DOHC.
 

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I have the exact symptoms, very hard shift to reverse, seems to be locked in 3rd gear, no check engine light, engine stumbles and occasional backfire to exhaust.

Sent my TCM and ECM to Modular Repair Pro in Van Nuys....
Never heard of this company, but many of our cars need computer service by people familiar with problems associated with them. That even changes with years of our cars. You need to supply info on your particular car and year for even people here to help, putting it in your profile will eliminate repeated questions about year, etc.

However limp mode (fail safe) with our platforms is most times caused by TCM, but not always. Also ’91 & ’92 TCM’s are subject to chip failure that some repair shops might not know to check for. Since you refer to (EEC 1)(?) maybe your car is in that date range.
 

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Check the TCM fuse
 
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