Hi guys, I have a Firebird I converted from V6/5spd to V8 auto. It is a CCC carbed car. I used all emissions equipment and computer controlled carb, etc. that is correct for the model year of the car body and ECU (1983). The engine runs great with no check engine lights. The only issue I am having with the car is that the torque converter locks up very very early (maybe as early as 15-20 mph) and then won't unlock unless you absolutely floor it.

The car runs with no check engine lights (just the usual code 12). I drove it for 3 hours on the highway with the converter locked cruising, no problems (except starting/stopping from toll booths with the early converter lockup ******* me down). I disconnected the converter tan/black wire and drove the 2nd half of the trip with it disconnected. The car drives perfect and is very responsive with the converter lockup disconnected. However I want to get the lockup functional for gas mileage/transmission temp. purposes.

What the heck is causing the converter to lock waaay too early, and remain locked too long? The TPS is working but I haven't checked it recently. I know it ranges properly, although it is probably off a few tenths of a volt at idle. I set it to 0.54v before I reset the idle speed. The TPS is not off enough at idle to throw a check engine light so it can't be off by much.

The transmission acts the same with or without the VSS connected (although when you disconnect the VSS it throws a check engine light). I didn't originally have the VSS connected because the V6 5 spd 1983 didn't use a VSS (although the VSS optical encoder came installed on the dash from the factory and was wired most of the way down to the ECU). When I realized the VSS was not connected to the ECU (due to the check engine light) I assumed attaching the VSS would fix it, but it didn't. Hooking the VSS up did eliminate the VSS check engine light but the lockup is still all screwed up.

Help!!!!

 

I'm having a similar problem. Mine locks up as soon as I get the 2nd gear upshift. I'm guessing there is a short to ground in the wire going to the lock-up solenoid. I just got the pan off, and am searching. I'll keep you posted.
Tim

 

If the lock up solenoid was shorted to ground it wouldn't ever lock up, would it? Does the lock up solenoid get power or ground from the ECU?

 

Most stuff lock up in 3rd or 4th. I believe some models are 2nd gear lock up. If so, this could explainit. Ride around with the scanner and look to see if the computer is commanding it.

 

The computer is commanding it on mine. I made the computer TCC solenoid output wire have a quick disconnect. When I disconnect it the TCC never locks up. It's not an internal trans problem. It's gotta be either VSS error or TPS error. If you put the pedal to the floor the TCC will unlock, it just takes way way too much throttle pressure to get it to do so. My trans definitely locks in 2nd gear, almost immediately when shifting into 2nd. No check engine lights though.

 

Install a manual on/off switch for the lock-up. This way you won't have to worry about it locking up too soon.

 

no no no no, no ghetto fixes with toggle switches. This is not operating as it should have from the factory, something is wrong with one or more sensors reporting to the ECU. It is not just a problem of me not liking the stock TCC lockup routine.

 

just a thought......I believe there is a vacuum switch under the hood of your car that will tell the trans (electrically of course) that you are at a high vacuum (like under low throttle application). If you disconnected the vacuum line running to this switch or it is otherwise malfuctioning, it could be your whole problem. As I recall, on my old 84' that I used to have there was 2 things which told the lockup to engage/disengage.......the vacuum switch told it to engage when under high vacuum, disengage under low vacuum. The brake switch told it to disengage when the brake was applied. Also the trans in your car should be capable of locking in 2, 3 or 4 but not first. A bad connection cannot be ruled out.

 

IROC212, it could be a short to ground somewhere or the TCC solenoid may be stuck.

327_TPI_77_Maro, can you read data on this one? if you can, what does the ECM say the speed is vs actual speed?

 

lowflyr, the vacuum switch was only used on non computer controlled carb cars/trucks. Mine does not use it, the computer alone commands lockup without any vac. signal stuff. I have not read the VSS, that is my next step. Something is screwy with a sensor the computer relies on for its TCC routine. The TCC solenoid being stuck is entirely possible, this trans sat out of a car for a really long time, and then it started behaving like this as soon as I started using it.

 

Using a test light on the ALDL terminals (A to F) will tell you whether the ecm is commanding lock up or not. Test light off-tranny locked (or brake switch open). ECM relies on steady TPS and Vac signal to command lock up. Your difficulty unlocking could be caused by a failure of the TPS to send a voltage change. Don't think that's it though, cause you would notice the loss in response.

Use the test light to determine whether it's tranny or ecm related and go from there.