Originally Posted by dukie564

you really need to forget about the timing being off...you're wasting your time. Timing off on straight 6 engines results in either the engine not starting, or a MASSIVE power loss and poor running. Basically you would see a lot more wrong than just failing an emissions test.

The fact that both your NOx and CO are high usually points directly at a bad cat. No other running conditions would cause both to occur at the same time on this engine.

I have a very important question for you though. Did you get the converter good and hot (eg: did you drive for at least 15-20 minutes (some at highway speed) before the test and keep the truck running while waiting in line)? This is very important to pass sniffer tests.

Originally Posted by je4reyk

Sounds like I really need to check the timing just to ease my mind ,because It's one thing I can do that's doesn't cost anything,who knows the flex plate might be off !