1991 late lockup
02-18-2017, 05:20 PM
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3rd Gear
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1991 late lockup
My roommate's C4 seems to be going into lockup late. He says its gotta be over 55 before it goes in and even then you gotta have a light touch on the pedal or itll come right back out. From what I've read, I thought it should go into lockup way sooner than that. Also, TPS was bad when he bought it and has now been changed. Is there a calibration procedure or something? Any other ideas?
03-04-2017, 10:39 AM
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Now I've gone and done it....
I tried the light thing sitting still and it didn't come on. Then, still sitting still in D, I tried grounding the TCC port on the ALDL, expecting it to grunt or something, but I got nothing. But now I may have really hosed things up....
In an effort to check and see if the computer had maybe been reprogrammed by someone in the past for later lockup, I disconnected the battery pos+, removed the ECM from above the battery, and popped the memcal to see if it was still the factory chip. It was, so I replaced everything just as it was. Now I have a REALLY strange problem.... The fans do not work. At all. AND to confuse things worse, normally, when you ground the diagnostic in the ALDL, it would trigger the fans. Now it triggers the A/C clutch instead. Also, when the car is idling, it keeps kicking the A/C compressor on, without idling up nor kicking the fans on, so I assume it THINKS it's kicking the fans on but eally kicking the A/C then too. And the dash controls don't seem to work the A/C anymore. I used a test light at the ECM to confirm it IS the ECM doing this. And, when I put the test light clamp on BAT+ and pierce the fan relay wire, it kicks the fan on, so I know the circuits are complete from the ECM out to the fans.
Could I have screwed up the ECM or MEMCAL by simply unplugging them?
If so, which one have I likely fried? Because of the late lockup anyway, I am considering buying a couple blank eeproms and a programmer. (it's way cheaper than the stock memcal anyway) I already found the stock bin for this car online and DL it.
Any suggestions??
In an effort to check and see if the computer had maybe been reprogrammed by someone in the past for later lockup, I disconnected the battery pos+, removed the ECM from above the battery, and popped the memcal to see if it was still the factory chip. It was, so I replaced everything just as it was. Now I have a REALLY strange problem.... The fans do not work. At all. AND to confuse things worse, normally, when you ground the diagnostic in the ALDL, it would trigger the fans. Now it triggers the A/C clutch instead. Also, when the car is idling, it keeps kicking the A/C compressor on, without idling up nor kicking the fans on, so I assume it THINKS it's kicking the fans on but eally kicking the A/C then too. And the dash controls don't seem to work the A/C anymore. I used a test light at the ECM to confirm it IS the ECM doing this. And, when I put the test light clamp on BAT+ and pierce the fan relay wire, it kicks the fan on, so I know the circuits are complete from the ECM out to the fans.
Could I have screwed up the ECM or MEMCAL by simply unplugging them?
If so, which one have I likely fried? Because of the late lockup anyway, I am considering buying a couple blank eeproms and a programmer. (it's way cheaper than the stock memcal anyway) I already found the stock bin for this car online and DL it.
Any suggestions??
Put a small indicator light bulb (like a 194) between ALDL A (top row inboard) and E (top row outboard). If an LED, put (+) on E and (-) on A. Go for a drive.
With foot OFF brake, light should be ON. When the ECM commands TCC = ON, the light will go OFF. If you step on brake, light will always be OFF, regardless of ECM command.
Compare the test light indications to the "feel" of the actual engagement. If the clutch doesn't follow the light closely, there are issues in the transmission, TCC solenoid, or the converter itself.
Another quick-check is to drive fast enough for TCC to be engaged. Lightly touch the brake without changing throttle, RPM should increase immediately about 200 RPM. Release the brake, and the clutch should re-engage in about 2 seconds.
With foot OFF brake, light should be ON. When the ECM commands TCC = ON, the light will go OFF. If you step on brake, light will always be OFF, regardless of ECM command.
Compare the test light indications to the "feel" of the actual engagement. If the clutch doesn't follow the light closely, there are issues in the transmission, TCC solenoid, or the converter itself.
Another quick-check is to drive fast enough for TCC to be engaged. Lightly touch the brake without changing throttle, RPM should increase immediately about 200 RPM. Release the brake, and the clutch should re-engage in about 2 seconds.