my 03 with 5.3 has a dead miss at idle ONLY...will literally jerk the truck but never die , then you acclerate and it is as smooth driving and running as can be... has done this for almost 2 years and finally got bad and has threw a code (cant remember #) but basically has killed that catalytic converter .....i have read where a misfire will kill the converter so first i need to fix the misfire then replace converters any ideas???? would never have Check engine light until recent , had no idea where to start.

 

Check Spark Plugs.
Clean throttle body. (controls idle)
Check for intake gasket leak.

Our 02 had a really bad idle right before we got the 07. Turns out it was the intake gasket had started a bad leak and running really lean. But fine off idle.

 

Check the spark plug wires.