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Problem with TCC coming and going.

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Old 07-09-2001, 08:08 PM
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Car: 1988 IROC-Z
Engine: 350 TPI
Transmission: 700R4 w/TransGo
Axle/Gears: BW 9-bolt w/3.73s
Problem with TCC coming and going.

I run my car over the weekend to a cruise-in and car show, over a nice hilly decent road.
One time I was in fourth going up hill about 60, and I noticed the TCC was pulling in and out, kind of like a surge condition. I know it didn't kick down to 3rd, since I manually shifted down and the rpm went up higher. I was giving it a little gas to maintain speed up the hill.

Amother time I was going around 50 up the hill and the TCC was also surging.

I have the TCC unlock prevent set at 60, and I lock/unlock the TCC in 4th at 50/45. Are these settings too high? I also noticed that GM had the difference between lock and unlock set at 2mph. This was consistent for many different bins. I don't think I hit the tables for unlock/lock for %TPS vs mph, since I didn't think I gave it enough throttle at those speeds. But I could be wrong since I didn't have my scan tool connected.

Today I scanned on the way to work, and no surge condtions were observed, so it seems to related to maintaining speed up hill under slight load.

Anyone got some suggestions? TIA

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Old 07-09-2001, 08:17 PM
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I had the same problem with "rolling hills". I found the TCC locking and unlocking, along with the EGR kicking in and out (you may not have noticed that one).

I found locking my TCC at a lower speed (45 MPH) along with controlling my EGR differently to prevent this "enable/disable" made highway cruising on "rolling hills" much smoother. Try keeping the TCC locked and EGR functioning.
Old 07-10-2001, 08:48 PM
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Car: 1988 IROC-Z
Engine: 350 TPI
Transmission: 700R4 w/TransGo
Axle/Gears: BW 9-bolt w/3.73s
That's kind of what I was planning on doing, just changing the TCC lock/unlock constants.
But what about that Unlock Prevent parameter? I understand it to be the value which the speed must drop below before the TCC can unlock. Hmmmm. So if I am set to 60, then below that the TCC can unlock? Guess I should lower that number.

I checked some recent scans, and I do believe the EGR is working. The duty cycle is flipping between 0 and 100%. I will most likely leave it alone for now.
Old 07-10-2001, 11:22 PM
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<font face="Verdana, Arial" size="2">Originally posted by MikeT 88IROC350:
That's kind of what I was planning on doing, just changing the TCC lock/unlock constants.
But what about that Unlock Prevent parameter? I understand it to be the value which the speed must drop below before the TCC can unlock. Hmmmm. So if I am set to 60, then below that the TCC can unlock? Guess I should lower that number.

I checked some recent scans, and I do believe the EGR is working. The duty cycle is flipping between 0 and 100%. I will most likely leave it alone for now.
</font>
FWIW, also look at operating temp., vs TCC enable. A 156dF enable with a 160dF can be lots of fun to figure out.

Old 07-10-2001, 11:22 PM
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<font face="Verdana, Arial" size="2">Originally posted by MikeT 88IROC350:
That's kind of what I was planning on doing, just changing the TCC lock/unlock constants.
But what about that Unlock Prevent parameter? I understand it to be the value which the speed must drop below before the TCC can unlock. Hmmmm. So if I am set to 60, then below that the TCC can unlock? Guess I should lower that number.

I checked some recent scans, and I do believe the EGR is working. The duty cycle is flipping between 0 and 100%. I will most likely leave it alone for now.
</font>
FWIW, also look at operating temp., vs TCC enable. A 156dF enable with a 160dF can be lots of fun to figure out.

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