Thanks guys for your input! (David, Andy and Bruce) I took your advice and investigated all of your suggestions. Through the process of elimination, I have been able to solve the excessive combustion problem ...it seems to be related to the CO adjustment. However, if I adjust the setting until the engine is no longer running hot and I have a nice steady idle at 950 rpms, I can not re-start the engine without turning up the CO adjustment again! Doesn't seem to matter if the engine is allowed to cool for a while or the restart attempt is made right after I shut the engine down. It won't start until I run CO adjustment up to the point where the engine starts but idles at 2000 rpm! (The plate is centered, no vacuum leaks and no kinked lines or fuel delivery problems.) Cold start valve malfunction maybe? Any other ideas? Thanks again. Rustproof vin 1559