Auto Tranny Probs - EVERYONE is baffled

[daswerve]

When I bought my car, it only had 5,549 miles on it. Never had any mechanical problems whatsoever for about 8 months or so. Out of nowhere, my auto tranny started losing it's mind: I wold put the car in Reverse to pull outta my driveway, and it wouldn't kick into gear for about 5 to 10 seconds, just seemed like it was still in park. Same thing when I would go to put it Drive.......hesitation, then it would engage. When I hit the street, for the first 5 minutes or so of driving it would slip outta gear and miss/rev high between 2nd and 3rd gears (it would also slip outta gear when making sharp right-hand turns, but not left turns) and would also stall at stoplights. So, still having a powertrain warranty, I took it to a Mitsu dealership....they told me the tranny was toast and ordered a new one........the first tranny came, they installed it, and told me it was now worse than before! They said the new tranny musta been wasted from the get-go, and ordered a second. With the second tranny installed, they said all was good and I picked up the car. It was perfect for a few months, but now it's doing it again! And the dealers has NO IDEA what's going on now......

Now, here's what I've noticed: my original tranny starting doing this in the middle of winter (cold weather), but was fine the previous summer (I bought it in May of 2001)......now that's it getting chilly again, my new tranny is starting to do it as well. It was fine all summer when it was 70-80 degrees in the morning, but now that the morning dew is rearing it's head again and it's colder, the problems are starting all over again......

I know NOTHING about auto trannys and the TCU.......but doesn't it seem as if we have a possible a cause and effect here? That maybe it's something electrical/temperature related? I'm at a total loss here, and so is the dealership.....

I've been searching forum after forum for over a year now and can't find anyone out there having this type of problem.......much thanx in advance

 

[Zerocygnal]

I had a similar problem with my Chrysler Cirrus. It had almost the same problems you described. I knew it wasn't the tranny...just a feeling in my gut, because sometimes it worked and sometimes it didn't. If a tranny goes...it usually just goes and thats the end of the story. This was intermittent so I started thinking TCU. Checked it out, everything was fine. I started going over the PCB board inside of the unit and discovered that they had sprayed a sealant over the board and circuitry that was desinged to seal it from moisture. However this same spray seal also contracted under cold conditions and put a strain on the board from the last 5 years of contracting and expaning via thermodyamics of the seasons. What was happening is that it was loosening the components on the board and causing them to "open" the circuit. Hence the intermittent problem until the car warmed up enough.

On another Cirrus I suspected the same thing, because it was having similar problems but a few new symtoms as well. That turned out to be a wire from the TCU harness that was pinched off by the bolt that secures the harness connector to the TCU itself. Cut, soldered, heatshrinked, worked like a charm ever since. My suggestion would be to first inspect the wiring to the TCU, then take the TCU to a dealership and have them test it. If all else fails you need to start using a multimeter and checking out the signals from the input data line on the TCU, make sure it is communicating with the ECU. If it is then check it at the other end of that wire..and yes..it's going to be a PITA to trace it without a wire map. It leads to the ECU wire color will most likely change on the ECU side of it. You can even take the TCU out and put the car in gear and back it in and out of the driveway, if the problem seems like it is gone with the TCU removed..then that is were I would begin analyzing.

Best of luck if you discover anything let me know. I don't think you had a transmission problem at all if you have replaced it 3 times now.

 

[daswerve]

I can't thank you enough for the quick and VERY informative response!

 

[Zerocygnal]

Not a problem, that is what I'm here for

 

[TalonRacer18]

what does tcu stand for? and where is it located at?

 

[Zerocygnal]

TCU=Transmission Control Unit.
On a Mitsubishi I do not know where it is located at. A 2g DSM may or may not have one, that I do not know. I know I've never seen one on a 1g. If I had my shop manual here with me I would look it up. Anyone else know?

 

[98TsiAWD]

I had an avenger ES v6 auto, When taking right corners the car would cutout terribly, like it was missing. But only on rights, WTF. So it had the TPS code up in the comp. So that was replaced. Didnt fix it, so checked spark plug wires, etc.

BTW, I thought it was the tranny acting up.

After months I finally found the problem, right below the engine computer when teh big wiring harness comes out of it, there was a metal strap the held it again the inner fender. It was cuttin into the TPS wire and groundign it to the chassis. Put liquid electrical tape on it, then taped it all up good, and I put elec. tape all around the metal bracket, screwed it back up. Ran like a dream ever since. The reason it was on on rigth is because the tranny shift linkage would push up slightly on the wring harness when the engine shifted on rights.

You could be having a simialr problem, look for metal brackets strapping wires to the firewall, fenders, etc. Make sure they arent cuttin into the wires.