Originally Posted by
Dr. Nopps
Yeah those cars seem to be an enigma wrapped in a mystery badged with a chevy logo to alot of people. Here's what may help: Look through your entire tune for any table that would allow you to command a specific AFR. I'm (not really) guessing the only one available to you is that one under the PE Mode tables. Set that entire table to your AFR content. (12.8 from earlier) Prevent your car from going closed loop in the tune, or physically. Perform a scan with a PID in the main table for logging commanded AFR, this is what the PCM is actually shooting for. Notice it will not be what you wanted, and may not seem consistant at times. In order to tune your car to run at 12.8 AFR I would think you should tell it to try and shoot for that, and then correct (in the tune) how far off you were from that figure. Perform the same type of scan but this time allowing the car to enter closed loop (it may take a few secconds) and running PE mode all the time any throttle 0% on up. As soon as you establish at least 1% throttle input, that PID for commanded AFR should read your desired 12.8 and stay that way untill you let off the throttle. Sorry about what you may have read but this leads me to strongly believe our cars are actually a mix of both. (Alpha-N & MAP) I don't have a backyard full of these cars of all different years to do testing on, so I really don't know about this next part but.- The cavaliers could all be like this untill they started using MAF sensors. In fact it would be hard for me to believe otherwise unless I saw a tune for one with the right tables. Even then I would still want to do a scan on it and see for myself exactly how it's thinking/functioning in regards to openloop vs. closed loop, fueling & AFR commanding.