Cylinders misfiring
Asked by abehilo Jan 31, 2015 at 04:19 PM about the 2003 GMC Sierra 1500 SLT 4WD Extended Cab LB
Question type: Maintenance & Repair
Cylinders randomly misfires when hot. Manifold gaskets, fuel injectors on the odd
number cylinders, M.A.F. sensor, crank shaft sensor, spark plugs, and O2 sensor
were replaced. The funny thing is, after every items were replaced [in these order] on
test runs, truck runs fine, until engine gets hot. The latest diagnoses was cylinders
were slightly misfiring truck could still run good and catalytic converter not performing
up to par which maybe due to it being plugged. Did as recommended fuel treatment
were placed in fuel tank. Truck ran really smooth for a period of time where I thought
problem was solved until it started major misfiring again. Any thoughts or suggestions?
I would appreciate it.
6 Answers
Appreciate your answer. At the suggestion from a mechanic, I did fill my gas tank which was half empty w/chevron techron gas. Also added a packet of X-treme fuel treatment at his advise I guess to mix w/the present fuel? As I mentioned, truck did run smooth after running it a couple of miles. It continued to run smooth for I estimate another 2-3 miles and started misfiring again?
Thanks. That's my next move. The misfiring are randomly happening with all of the cylinders when hot. It started with 1-3-5-7 cylinders, jumped to 5 and 6, now and then 2 and 4 would pop up. The last read out was most of the cylinders including 8. It's just jumping around at random.
Yes, the boots seemed to fine. Did not see any cracks or signs of wear. No, I didn't know that the boots needed to be greased?
I've got the same problem. 98 gmc extra cab 5.7 z71. Misfires at steady throttle or cruise . No problem accelerating. Will still smoke the tires. Seems worse when cold. New cap , rotary button, plugs. Driving me crazy. Had one guy tell me the modal in the distributor was going bad. I just don't know.
