stalling and shift problems

[macmade22]

my 97 gst will completely go dead at stops, like when leaving my driveway or at stop lights. The car isn't in the best of shape i am doing a lot of work to it right now. also i noticed when i bought the car (it is an automatic) it would down shift by itself no big problem at the time it would happen around 30-45 mph, a few days ago it downshifted by itself from overdrive to drive when i was doing 80 mph. the check engine light came on directly. after driving it today i noticed that when i start from stop it is very very slow until about 30 mph. I tried dropping it in low gear it dose not work it will work in 2, i took it to the highway, and noticed it will not go into over drive, i have had the tranny rebuilt a year ago for $3500.00 in atlanta, im just wondering what could be causing this? the guys at the shop can't figure it out and when he tried to see what the error code was he got no response. is this a pcm/ecu issue or do i need a new tranny/rebuild?

 

[97SpydermanGST]

Does it stall out when you come to a stop or does the car just turn off? Could possibly be your stall converter. Also the Downshiting is something called Brake assist (something along those lines). There is a description in the car's owners manual about it. It just downshifts your car when you are braking and going down a hill.

 

[macmade22]

it stalls at stops it doesn't turn off it just falls below 500 rpm and then dies i can catch it most of the time when i hit the gas. i know about the brake assist, this is nothing like that i was at 80 mph and it down shifted from over drive to drive, i had to slow down to 55 mph just to keep it at normal rpm range. but it will not go into overdrive at all and it will not take off in low or second. it seems like the only gear i have is drive i don't know what is going on thats why i thought maybe the pcm cause that controls shifting in automatic transmissions, i just dont want to spend the money on the wrong thing.

 

[97SpydermanGST]

The stalling when coming to a stop sign problem happend to me to. I was thinking that it was stall converter, but before I changed it out I had the the transmission fluhed out and that fixed it completly. It was like 60 dollars at a jiffy lube. Im not telling you that would fix it, but it took car of my problem. As far as the downshifting problem it might be the TCU, Not really sure what is going on with that one. There is a problem with some of these car called "limp Mode" this might be your problem. Do a little researching about it, i know there is a lot of info on it.

 

[97SpydermanGST]

Any luck with the car yet?

 

[macmade22]

I took what you said and looked into it, about limp mode. I search the forum somone had the exact same problem he fixed by changing out a 10 amp fuse for the transmission under the dask board, so i have done that haven't tried to run it yet, I am pretty much doing a whole engine overhaul, i pulled the valve cover and exhaust manifold off, so I can't crank it right now. will see in a week or so, I seen something else on her about a two button shifter for automatic tranny. that might be something ill look into.