I'm posting this for my friend.
He has a 1999 GXE 5 speed with about 160,000 miles. His CPU gave him 3 codes: 0304, 0309 and 0705. 0309 code doesn't even exist so I don't know whats that all about.
His car is acting very weird. In any gear after 20 mph it would jump for no reason. By jump I mean like an auto transmission when it shifts hard between gears. RPMs don't drop and function normally. A week ago it was just a single jump but today it was 3 of them in a row. THis is going on when he is driving in gear not when he is shifting.
What could this possibly be?
Any help is appreciated.

 

He's lifting his foot off the gas enough that the drivetrain slop is giving a bucking feeling.

You've got to be very smooth with the throttle to avoid that bucking response when you are in gear and go from throttle to engine braking.

Dave

 

I'm pretty sure he knows how to drive stick since all of his cars had manual.

 

There isn't really anthing inside the tranny that would do such a thing, unless there are major problems inside, in which case you'd hear a lot of noise too.

Clutch, maybe, but I'd suspect something is causing the engine to buck.

Dave

 

Well it seems like its something with the engine.
It feels like the engine is dieing off and then out of nowhere the power comes back, but everything happens within a second. I just used auto trans shifting to describe how it feels.

 

I'd start with the small stuff, check battery terminals and ground wires, a loose ground wire will do that exact thing, double check all connections, vacuum lines, etc