So I took my 2000 C70 HT 5 speed out to the highway to see what it's got, stepped on the gas hard, RPM went up to around 4000 with no problem but then car started jerking and check engine light started flashing. The check engine light has been on steady since we bought the car - about two weeks ago - with no apparent problems but this time it started to flash. I let up the accelerator and a minute later the light went back on steady again. I tried accelerating hard again and the result was the same: jerking, flashing check engine light. I then tried 'normal' acceleration, worked great, I could go over 5000 RPM, went from 80 to 100 MPH smooth. Anyone with any ideas? Anything I should check first? Also would like to mention that standing on driveway in neutral engine will not rev up above around 4000 RPM, no jerking just will not go above that.

 

Flashing means misfiring, not good.

Start with this.