GMC Envoy 2003 Engine Shake and Rough Idle.
I bought my Envoy 2003 XL SLT 4.2L just in Dec 2011 and performed necessary maintenance which included replacement of all breaks, Engine Synthetic Oil/Filter, AC Delco Spark Plugs, Transmission Oil/Filter and Fuel Filter and cleaned Throttle body, Replace Ignition Coil # 1, Cam Actuator, Engine Side O2 Sensor and CAT. In addition to this I have performed Fuel Injector cleaning by One Stop service Center upon recommendation of GM Mechanic who notices pinging on Fuel Injectors.
I am noticing engine shake at the time of engine start and stop (Switch off). In addition to this I have rough idle problem when accelerate or stop at signal light. RPM fluctuate from 615 to 300 and back within 2 second. It does not matter whether is cold or warm start. sometime it is hard running on first gear and sometime it seems smooth. SES light is also on.
I have been searching and found some articles which indicated that either the Motor mount need to be replaced or Plugs with NGK ILTRB11 (3474).
Last month I just opened first three Plugs and I found carbon fouled. If this is a problem then can you advise me what to do next.:confused::crazy:
Thanks a lot for your assistance in advance.