I have a 1987 Camaro 305 TPI that starts and idles great, but when you try to maintain a steady speed (45, 50, 55, etc..) and your kind of just feathering the gas pedal it, will backfire through exhaust and just run real crappy. If you push hard on the pedal you can get through it, but trying to maintain a steady speed is tough. It's been on the scanner twice, replaced almost everything (except EGR Value and Solenoid) and still can't pin it down. If you put ECM in service mode it runs fine (but we don't want to run it this way). I could really use some clear thoughts on what to check or change. thanks in advance

The egr is supposed to be working during light-throttle cruising. I would start by checking that the egr valve moves up and down freely, make sure all the vacuum lines are connected and that there aren't any splits in them. Aside from that, I would rule out all the simple things. Check the timing, ohm the injectors, check the fuel pressure, check the ignition system, etc. Check that the TPS reads .54 volts at idle, and with the ignition on but the engine not running, slowly open the throttle body all the way and check that the voltage has a steady increase to somewhere between 4.5 and 5 volts.

have u tried cleaning ur mass air sensor?

Thanks. I did disconnect the EGR soleinoid and it doesn't seem to make any difference it how it runs. Not exactly sure what that means, but I'll reconnect and try to see if I can verify the EGR valve is working. Any tricks on testing the EGR? It's tough to see under the throttle body.

thanks for responding.

I replaced the MAF a while back and it seems to be clean and working properly.

thanks for responding.