Hello
I have 1995 monte carlo 3.1 car drives fine till you get the speed up to between 80 and 100 kms the car starts to shudder even worse going up hills and when i push the accelarator all the way down the power is there no shudder just shudders when your cruising between 80 and 100

Thanks
any help will be grateful

Bad wire, plug, coil, weak injector, more uncommon could be a failing torque convertor clutch. Should be scanned for misfire counts to start with or just a full tune.

sorry I forgot mention the car was in the auto shop all day yesterday all the plugs are fireing new wires all injectors are working good pressure they swaped the coils with new one's still no difference checked the TP it's working they replaced the fuel filter. He dosen't think it's the the torque converter. The only problem is he cannot get a reading from the scanner there's no communacation to the computer. The strange thing is in the moring when you first start the car you can drive it for the about 30kms before it starts to act up. This happened after i replaced the starter

Thanks

Car needs to be driven when this happens with the scanner working, in the hands of a competent diagnostician to trace the problem, no other way short of random parts replacement. The non- comm issue must be addressed first of course.

sorry I forgot mention the car was in the auto shop all day yesterday all the plugs are fireing new wires all injectors are working good pressure they swaped the coils with new one's still no difference checked the TP it's working they replaced the fuel filter. He dosen't think it's the the torque converter. The only problem is he cannot get a reading from the scanner there's no communacation to the computer. The strange thing is in the moring when you first start the car you can drive it for the about 30kms before it starts to act up. This happened after i replaced the starter

Thanks

this to me is a crank position sensor not too expensive and this is suspect as well as wire/connector/connections..to/from it. this will give communication error as well....very similar to bad wires/plugs in feel of failure..