My husband got our 92 diamante from a friend. our transmission is stuck in third gear, and we have one to replace it, but there is another problem that we cannot seem to address. when the car is in park, it doesnt have a problem, but once you get out on the roads and the car gets going, it will jolt forward, and the check engine light will come on. sometimes it only does this once, other times it does it constantly(when it does this you can hear clicking under the passenger side dash) then it just cuts out completely. I was the last person to drive the car. on the way home it jolted forward again, and the rpm gague went to nothing, there was no response when I tried to accelerate either, yet the engine was still running. If anyone would be able to shed some light as to what this problem may be, I'd greatly appreciate it. I love this car, and I dont want to lose it.

 

It does sound like a transmission issue. The only thing I can think of is that the transmission has the wrong fluid in it. Autos can be very finicky with their fluids. Another consideration is the torque converter, PCM (powertrain computer module), solenoid pack, and then the transmission itself. Then there's also the speed sensors and other sensors that can put your car into "limp mode".

The least costly, I think, thing to do is to have the transmission fluid completely flushed out and have Mitsu ATF+3 or +4 put in. The fluid seems to also be a common thing with Mitsu/Chrysler automatic transmissions.
If you can make it to Autozone or the likes, get them to read the codes (they do it for free).

Another question for you before I go is...does your car do this when it's cold or when it's warmed up, or does it do it regardless of engine temp?
If it starts acting up when th motor gets up to temp and when it's been driven awhile, it is most likely the tranny fluid. That I can tell you for sure and is very universal. That clicking makes me think of an ASD relay, although, I'm not as versed with your vehicle platform. Oh yeah, the jolting sounds to be transmission related also, almost as if the torque converter is going out or it doesn't have enough pressure to lock the plates...but that goes back to the fluid and not having the correct type.
Regardless, have the code(s) read at Autozone so that we can help you a bit better.

..and welcome to MF Murasakinamida.

 

The car wont even make it out of the apartment complex now, and it doesnt matter what the temp is, it keeps doing it. and now that i remember it. my husband got in it a few days ago, and was going to drive it to the end of the complex. he got there, but it cut out on him before he could get back. when he finally managed to get it back, he sat there for a minute, and we noticed this strange sound ( it can only be heard sitting inside) we also noticed it was coming from beneath us, and kind of ruled out the exhaust, seeing as you couldnt hear it standing outside.

 

alright, i talked to my husband to be able to give you a better understanding. he says that its described as a massive loss of acceleration. the ECM relay clicks rapidly in time with the engine, until the engine dies out. it works alright while the car is cold now, but if it barely starts to warm up and it will die out again. Smells a bit like its flooding itself out during the "clicking fit", as i call it. Thats what he says is wrong with the car, along with the transmission being stuck in third gear.

 

we found out what the problem was. It turns out that my car is in a line up of models that come from the factory with a faulty capacitor in the ECM. the warranty is expired, but im pretty sure I can get another one for a decent price. Thanks for trying to help me.