96 Yukon Running Very Rough - Timing?

[cwf82]

I recently had the motor replaced in my Yukon and the new motor will not run correctly.

When hooked up to a scanner is says the timing is out -24 degrees. It will idle but it's very rough. Double checked the distributor to make sure it isn't off a tooth and it is good. Tried moving it a tooth just to see if it would help and it only made things worse. Also throwing a MAF code which I think is a false code. I switched out the MAF with a known good one and it still gives the code. The crank sensor is new, the cam sensor has been checked. All cylinders have good compression, spark plug wires have been ohmed and appear good. New dist cap and rotor, new spark plugs, new wires.

My mechanic and myself are completely stumped. Anything you guys can think of that would cause this?

[jadimon]

I don't know about timing or how your truck runs under load, but the egr and air idle control valve could be the problem. Have you looked them over?

[Firefighter6112]

Had a issue like this in the past with a truck with the same motor, ended up being a vaccume issue. check the vaccume lines also.