98 K1500 5.7 vortec Rough Idle

[Silverado418]

To start off the truck runs great other than the shakes at low rpms, and has been this way for 7,500 miles when I bought the truck 8 months ago.

 

The problem does not occur when the engine is cold, only when warmed up and doesnt happen everytime it is warm. It feels as the truck wants to jump off the brake as it shakes, if put in park the truck continues to shake. Rpms so not bounce around and are around 1100 cold, 600 warm. No codes or misfires.

The following has been replaced throughout the 8 months without effect:

 

Distributor gear, rotor and cap, intake manifold gaskets, water pump, and other small sensors.

I have heard that idle air control valve could be the issue, the spider fuel injectors leaking fuel, fuel filter, vacuum leak.

Any help or advice would be very appreciated!

[bubba1916]

have the o2 sensors checked heater went out in one of mine wreked havoc till it got cold enough out side to set a code was getting 12.2 mpg coulnt figure it out till it popped the code also ive noticed when it was idleing rough the fuel relay was getting hot on me looked into it and found out my oil pressure switch had went bad that was also an issue of mine may not be related to your problem would be worth looking into any how o2 sensors changed getting 18.8 now and rough idle gone smooth from park to drive now no lugging

[Jeep_Comanche17]

i would run some seafoam or fuel additive to clean the lines and injectors. also check the idle sensor one of those went bad in my gramps old 350 and it was a nightmare trying to keep that thing idling. good luck!