Accepted Answer

Alright there are a couple of things to check here.

The simplest thing to do as a first step would be to run some injector cleaner through the engine. When it's kicking into low gear to give some extra pull the engine might not be getting enough fuel through a partially clogged injector (or injectors) and be causing your miss and smoke.

If that doesn't help (and I'm not too sure it will but it could and it won't cost you but a couple bucks and no time at all to do so it's worth a first shot) you might look at the EGR Valve. When your truck is kicking down for extra power the EGR may be failing a bit on you causing too much excess oxygen to enter the chambers which would cause your smoke and missing. This seems like the most likely problem but it's obviously a more expensive and intricate fix so I'd definitely run some injector cleaner first just in case you luck out with that $5.00 investment solving your problem.

Expert:	Matt Kesler
Pos. Feedback:	98.8 %
Accepts:
Answered:	7/7/2007

ASE Certified Mechanic

20+ years experience