[silicon212]

Originally Posted by RobertPitre

I have a 2009 corvette, I purchased this car from a family , the car sat up for a while, they would just crank it up every now and then. Well I purchased it and the engine light is on and the TCS light goes off and on. Well I bought it to a certified mechanic for him to repair it, he ran a test on it and it showed a 0300 code, misfiring code. Well he changed the plugs, wires, sensors, did smoke test, checked filters, we running 93 oct. with fuel cleaner and still engine light on, we don’t feel no misfiring ,when running down the road, but we feel a rough idle and the rpm needle is not bouncing on idle , but running I can see rpm needle drop from 1600 to 1000. Now the TCS light will go off and on, the mechanic feels that the TCS light is coming on due to the engine light is staying on. He changed the coil also, made sure nothing clogged up for air intake to engine. The engine run great but it has that rough at idle . Starts right up with no problems. I don’t want to have the engine light turn off by program it to not recognize there is a misfire code going on. Does anyone have any experience with this problem or can you provide some insight on how to fix this problem. I would appreciate any assistance with this problem thank you very much.

Older post, I don't get here that much. GM often doesn't actually tell you which cylinder is misfiring via DTC on stuff newer than say 2000. It will just give you the generic P0300 and let you figure it out. You'll need to put a scan tool on it and check for misfires on individual cylinders that way - my Snap On Apollo D8 has this function for GM and most should. Check the '180 out' cylinders as well as the indicated cylinders - I've noticed on many GMs that a misfire indicated is actually on the cylinder 180 out aka a Cyl 5 indicated misfire is actually occurring on Cyl 8. Cyl 6 is the 180 from cyl 1 etc. so 1-8-7-2 6-5-4-3 is the firing order on an LS/LT engine, you can see the 180 out cylinders (180 degrees of CAMSHAFT revolution).