I have a 2003 GMC Sierra 1500, 4wd, 97,000 miles, 5.3L. A couple weeks ago, it began to idle rough and is difficult to stay running 1st thing in the morning. It will often die on me unless I feather the throttle. After about 15-30 seconds of feathering the throttle and revving it to between 2-3K, it will stay running, but still idles rough and drops to about 600 rpm at idle. It only seems to have difficulty idling after sitting for long periods (i.E. Over night)
The Service Engine Soon light cam on, so I hooked it up to a diagnostic scanner, which showed code P0300 "random/multiple cylinder misfire detected". I have replaced the fuel filter and spark plugs (the center electrodes were pretty worn, but all cylinders looked like they were burning good), but the problem still persists. I don't see any vacuum or other hoses unhooked or cracked. The symptoms seem to be similar to a choke malfunction on a carburated engine. Any thoughts?
Wednesday, November 24th, 2010 AT 4:10 PM