98 Tahoe ruff idle when it warms up

ChrisWalter · December 20, 2011

When I first start it up cold the idle is fine. After it warms up the idle is ruff. Above 1500 rpm it smooths out. Seeing codes P0300 and P0172. Any help would very appreciated.

AirForceAngler · December 20, 2011

P0300 is random misfire and your rough idle. Something wrong in the ignition.

P0172 is an over rich condition in bank 1, left side of engine. If you fix P0300, this one will probably go away. Sounds like you have a misfire condition on the left side of the engine. Start with replacing plugs and plug wires and see where it goes from there.

ChrisWalter · December 23, 2011

Thanks for the reply. I replaced the plugs didn't help. Would the plugs and or wires change as the engine warms up?

ChrisWalter · December 28, 2011

Anyone have anything to add.

AirForceAngler · December 28, 2011

_{Did you replace the wires? You may also look at replacing the cap and rotor also plus check for vacuum leaks. There are lots of things that can lead to the misfires.}