Does ECM control A/T shifting?

Okay, I'll begin by telling you the problem...then what I've done so far...anything further information that one can provide would be most appreciated. 87' 2.0 Si A/T. At first start....engine accelerates through first gear, when it hits second it revs at high RPM's and slowly grabs the gear usually w/ shuttering. The same happens for third w/ less shuttering, and it will usually do fine into fourth, maybe a tiny rev before it grabs it. Now then, once I am at say 65 and cruising along it will down shift out of no where and practically lunge me into the steering wheel. A quick drop to neutral and a quick rev or two and then dropped back into D4 it will cruise right along again in the proper gear. Then if I hit a red light and go back through the gears it will do the same thing except this time it hangs in third, then catches fourth, then drops back again to third and will stick. I've had it @ 6200 and will not shift for anything....neutral and reving does nothing at this point. However, when the back and forth shifting is occuring and I put it in nuetral and shut the car off for about 5 - 10 seconds recrank and drop it in D4 it drops right into the gear it's supposed to and runs fine until the next red light then it starts all over again. Now this problem all began when I purchased the car. The persons who owned the car before me had installed a CV axle that was about 1/4 inch to long and it had about a 1/4 gap where it should seal into the transmission. Thus I was initially pouring transmission fluid in until I could replace the axle. Once I replaced the axle, flushed the tranny 4 times, and replaced w/ high milage tranny fluid and Lucas I expected it to run like a champ....I also checked that the passing and throttle cable adjustments were correct...but low and behold still the tranny is acting sickly....So this leads me to believe that my ECM may be involved. Though I am not getting any codes and the PGM FI dummy light has never come on, my instincts are pulling me in this direction. The only other thing I can think of is that there is a sensor that has gone bad...is there such a sensor that controls shifting?....or is it the ECM?....is there a vacuum for the tranny like on older Fords, could it be not enough vacuum?...or...and I have been avoiding this question until last.....is the tranny shot? Thank you in advance for any insight into this dilemma.

Yeah the ECU controlls the automatic transmission, at least on the 3rd gens they do, and I'm sure they do on yours as well. Even though the ECU controlls the tranny, that doesn't mean that the problem is purely electrical, it could very well be a mechanical problem, such as the Valve Body. I would just go get it checked out by someone who knows what's up with it...
Also, ask on DoitYourSelf.com in the automotive section, there are a lot of ASE Techs on that site ready to help you out with reliable information.

Okay, I'll begin by telling you the problem...then what I've done so far...anything further information that one can provide would be most appreciated. 87' 2.0 Si A/T. At first start....engine accelerates through first gear, when it hits second it revs at high RPM's and slowly grabs the gear usually w/ shuttering. The same happens for third w/ less shuttering, and it will usually do fine into fourth, maybe a tiny rev before it grabs it. Now then, once I am at say 65 and cruising along it will down shift out of no where and practically lunge me into the steering wheel. A quick drop to neutral and a quick rev or two and then dropped back into D4 it will cruise right along again in the proper gear. Then if I hit a red light and go back through the gears it will do the same thing except this time it hangs in third, then catches fourth, then drops back again to third and will stick. I've had it @ 6200 and will not shift for anything....neutral and reving does nothing at this point. However, when the back and forth shifting is occuring and I put it in nuetral and shut the car off for about 5 - 10 seconds recrank and drop it in D4 it drops right into the gear it's supposed to and runs fine until the next red light then it starts all over again. Now this problem all began when I purchased the car. The persons who owned the car before me had installed a CV axle that was about 1/4 inch to long and it had about a 1/4 gap where it should seal into the transmission. Thus I was initially pouring transmission fluid in until I could replace the axle. Once I replaced the axle, flushed the tranny 4 times, and replaced w/ high milage tranny fluid and Lucas I expected it to run like a champ....I also checked that the passing and throttle cable adjustments were correct...but low and behold still the tranny is acting sickly....So this leads me to believe that my ECM may be involved. Though I am not getting any codes and the PGM FI dummy light has never come on, my instincts are pulling me in this direction. The only other thing I can think of is that there is a sensor that has gone bad...is there such a sensor that controls shifting?....or is it the ECM?....is there a vacuum for the tranny like on older Fords, could it be not enough vacuum?...or...and I have been avoiding this question until last.....is the tranny shot? Thank you in advance for any insight into this dilemma.


TCM is always the last thing to blame. TCM receive signal from various sensors on your engine and send signal back to your shift control solenoid valve or modulators. That means shifting is controlled by modulator pressure depending on engine load and throttle valve linkage position. Make sure your throttle linkage is adjusted to specs and sensors are operating properly (check wiring connections for open, short and grounded sensor circuits ).

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Found the problem....catalytic converter and muffler were clogged ...severely....cut it out and welded a straight pipe on and abra cadabra....runs like new....thanks for your help....and I look forward to participating in this forum....

Found the problem....catalytic converter and muffler were clogged ...severely....cut it out and welded a straight pipe on and abra cadabra....runs like new....thanks for your help....and I look forward to participating in this forum....


I really doubt that was the problem. Your engine will not even start if cat converter or muffler is severely clogged. You said you can drive around accelerating your engine but your tranny is shifting badly.

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