Bear with me, this is a long one, but interesting.

Since I bought the car, the ECM has been disconnected, and recently I tried to hook it up, but the car stalls unless I keep the gas slightly depressed. The does not, however, stall when the car is above operating temperature and the fan kicks on, but idles really low. Without the ECM hooked up, the car idles high (1100rpm) and burns rich (I attribute this to the Air mixture solenoid stuck open because the ECM isn't on). When I do hook up the ECM and start to drive, the car reacts fine until it hits fourth gear. When the car hits fourth gear the rpm's drop from ~1800-2000 rpm's to 1100 rpm's and the car jerks hard, and does not pick up much more speed. When the ECM isn't hooked up the rpm's do drop lower than expected in 4th gear, but the car does not jerk.

With this said, anyone have ANY idea what I may be dealing with?

 

I would start by verifying that the ecm and chip are the right ones. Also, check your throttle valve cable for the tranny. Make sure it is not broken and still connected to the tb or carb.

 

How would I verify that the ECM and chip are the right set for the car? I should probably also mention that when the ECM is hooked up and driven around I recieve no error codes (aside from code 12)

 

Should be able to google search the ecm part# and chip by your year and if tbi or tpi, then check your ecm.

 

Sounds like your computer is locking the converter before fourth gear is fully engaged. This will fail the transmission.

 

Any test for this?

 

Time to take this to the sub forum for transmissions. Those guys might know.

 

That's what I first thought, but I believe this has very little (if anything) to do with the transmission... The problems with the Carb/ECM seem to stick out more to me than the transmission. This problem just seemed to be effected by multiple systems, so I thought General was the way to go