92 Corvette LT1. I have been fighting a problem with my car having a rough idle and all the way up through 2k rpm or so. Did some datalogging today and realized that at idle I have roughly 21 to 23 degrees of timing (jumps around), but when i slowly increase engine speed to 1000 or 1200 rpm, the timing actually drops down to about 20 degrees. I compared it to some of the datalogs from my 96Z and it had about 30 degrees of timing by that point. This is all sitting still. Car runs strong at full throttle, but part throttle and idle sucks! I have swapped ignition module, map sensor, wires, plugs, and had the opti off to look at it, all to no avail. Please help!!!!!

 

The viewed timing in datamaster is commanded not necessarily what is happening. If the number is low in dataamaster something is causing the pcm to command low timing. Could be a programming issue or some sort of mechanical/sensor issue causing that.

 

Is the grommet at the map sensor OK???

 

Is the programming stock, or has it been tuned?

 

Programming is basically stock. I have burnt a chip with the egr removed but nothing else. No timing changes. Grommet appears to be ok at the MAP sensor, and the MAP sensor readings seem to be good and move like they should while watching the datalog. I also don't have any spark retard showing at this point either on a datalog. Very weird problem.