I thought I had an ignition/timing/whatever problem causing what I thought was "missing" around 2300-2500 rpm, 45-50 mph in 1988 GT 2800 6 cyl automatic trans with, I'm pretty shur, the high final drive ratio. Idle seems normal, nothing weird about putting foot on gas for going up hill or speeding up, but the last several months have had this rapid [like seconds] frequency, intermittent "dragging" effect when cruising along at above mentioned rpm's/mph's.

Local shop guy told me the GM transmissions of the 1988 era had some problems trying, and not quite making, and trying again ["searching"] to "lock up" at moderately high/cruising speeds coupled with relatively low power/load requirements, like along a level highway. He said GM changed to programable computers about the time this problem came to light, and that the 1988 and early 1990s era GM trans-controlling computers had to have a "PROM" chip physically replaced to fix this issue.

He also said the obvious when I questioned, "No, hit hain't gonna hurt anything iffin you replace the plugs and wires" - but hit looks like to me an ignition issue would not be so rpm-mph-load specific. The same shop already replaced, to fix a start & run problem, damn near everything electric from the distributor shaft up a few months ago for several hundred dollars. Just not the wires or plugs.

Is this computer/transmission story real? If so, how can I get the fix PROM?

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John W. Tilford

I haven't a clue about the story, but if you think the lockup torque converter is the cause, unplug the connector on the tranny (under the rubber air intake) and see if it goes away. If it does then there is an issue with the lockup torque converter which may be mechanical or electrical in nature.

the torque converter lockup is at best a 200RPM difference. it sounds more like you are not going into 3rd gear. and, that would be a problem with the TV (Throttle Valve) cable, which goes from the throttle body, wraps around the front of the motor, then enters the transmission near the center, top.

some trans problems feel like misfires, its crazy. at that speed too, ive replaced whole ign. systems to try to fix it and it doesnt do anything. replace the trans.
of course if youre plugs and wires/coil is all messed up then it could be that too, or both.

Thanks, it's good to know it may not be my imagination, even though the "surging" is not exactly snapping my head and neck back and forth - it's pretty subtle.

No, it's shifting into third OK. I can feel and watch [on the tach] each shift.

Is there any more to tell about the diagnostic of unplugging a connector under the air cleaner? Unplug and test drive? Any chance of unplugging the wrong connector and the world blowing up?

There are only 2 electrical connectors on the 125 so it is difficult to get them mixed up... The VSS on the passenger side of the transmission output shaft and the TCC on the front driver side of the trans (4 pin connector very similar to the IAC connector on the throttle body). All it does is lock up the torque converter and will not harm anything if you dirve with it disconnected. I do not recommend driving it forever with it disconnected, but you can run it that way to prove or disprove the lock up torque converter is the culprit.

Thank you, Guru!

If the unplugged trial fixes the phantom "missing", what's the real fix? Back to those mysterious "prom" chips the local shop talked about? That dint sound too bad, if the new-programmed chips are available.

Next I'll have you virtually disassemble the door and re-slider-pad my passenger window, re-gasket my whistling sun roof, fix the small hole in the drivers seat cushion, restore sound on the right/passenger side speakers, tell me how to get those stupid long tail light pod screws to line up with the threaded clips, and drop in a 3.4 to replace the 2.8.

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John W. Tilford

quote Originally posted by John W. Tilford: Thank you, Guru! If the unplugged trial fixes the phantom "missing", what's the real fix? Back to those mysterious "prom" chips the local shop talked about? That dint sound too bad, if the new-programmed chips are available.

Replace the torque convertor lockup switch in the transmission as it is not holding.

quote Originally posted by John W. Tilford: Next I'll have you virtually disassemble the door and re-slider-pad my passenger window, re-gasket my whistling sun roof, fix the small hole in the drivers seat cushion, restore sound on the right/passenger side speakers, tell me how to get those stupid long tail light pod screws to line up with the threaded clips, and drop in a 3.4 to replace the 2.8.

Just push those screws down and start turning, they will self align. I put a dab of silicon brake lube on the threads so they turn easier.
The 3.4 is a direct drop in for the 2.8, nothing to it.

Replacing the torque converter lock up switch - is that like, you know, hard to do? Require brains and labor? Or is there an obvious, easy to get to, electrical switch outside the transmission housing somewhere? You are going to say it's inside the transmission, aren't you?

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John W. Tilford

quote Originally posted by John W. Tilford: You are going to say it's inside the transmission, aren't you?

Yes he is.....

But you only need to access the side cover to get to it.

BTW, is Buffa Louies still there in Bloomington? YUM! (Yeah, I lived there for awhile long ago...)

[This message has been edited by randye (edited 05-16-2008).]

Yup, Buffa took over the old Gables (as in Stardust Hoagy Carmichael) location just west of the old IU campus. I forget what restaurant was there between the Gables time and Buffa, something not too great, obviously. Buffa has a nice billboard between Martinsville and Blmtn, billboard styled like a Hooters ad, as I recall. Don't get north too often. Had to drive to Indy too many years from Monroe County.

http://www.buffalouies.com/locations.html

Taking off the side cover - like from below the car? Like, all the nice red fluid comes out? Where get replacement lock up switch? Santa?

quote Originally posted by John W. Tilford: Yup, Buffa took over the old Gables (as in Stardust Hoagy Carmichael) location just west of the old IU campus. I forget what restaurant was there between the Gables time and Buffa, something not too great, obviously. Buffa has a nice billboard between Martinsville and Blmtn, billboard styled like a Hooters ad, as I recall. Don't get north too often. Had to drive to Indy too many years from Monroe County. http://www.buffalouies.com/locations.html Taking off the side cover - like from below the car? Like, all the nice red fluid comes out? Where get replacement lock up switch? Santa?

Yes the red juice will come out...at least some of it.

Lookie here ---> https://www.fiero.nl/forum/A...050119-2-055302.html

and here ----> http://www.kichline.com/chuck/fiero/TCC.htm

Randye, thanks!

Does the "third gear switch" referred to in the first URL/thread you provided coincide/same-same with the second referring to the "lock-up" switch? I.e., are these two versions of the same job? The solenoids sound the same. I thought both read well, and the second exceptionally well.
jt

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John W. Tilford