Engine flooding when cold

[Tungsten]

I have this really weird problem on cold starts and only while the engine is cold. Just before the temperature gauge reaches the C mark, if I rev the engine slightly or try to take off in D, the engine bogs down a little bit just before it revs back up. The problem instantly goes away after the truck warms up. Also, for some strange reason, the truck doesn't do this if the fan clutch is locked up while the truck is warming up. It only happens if the fan clutch gets free-wheeling on a cold start.

 

I am still trying to figure out what is wrong here. Maybe it could be this way because the exhaust system is flowing better (or worse lol). Or the timing being off during start-up?

 

I replaced the coolant temp sensor and the O2 sensor. I did a complete tune-up with new wires, spark plugs, cap, and rotor. Also, I fixed the MAF sensor wiring.

 

I found out that when the engine is cold, the O2 sensor output is ignored. So I guess the O2 sensor kicks in and solves the incorrect mixture problem. What can cause the incorrect mixture?

 

Is there anything else I can try?

Edited July 14, 2010 by Tungsten