2001 GMC Sonoma is misfiring again

gmc
misfire
sonoma

#1

I posted earlier today. My truck was diagnosed with having a bad u joint in its drive shaft.



I picked it up this afternoon and had a reoccurrance of another problem!



Three months ago I had a blinking check engine light - a multi cylinder misfire. My mechanic changed the plugs, wires, and an oxygen sensor. Today, it started misfiring again!



What’s my problem here?




#2

To clarify - he replaced the plugs, wires, and oxygen sensor in March. It ran fine…until today.


#3

When does the misfire occur, under heavy load, at idle, during steady cruise, at warmup? What engine do you have in this, the L4 or V6? Has the fuel filter been changed and the fuel pressure checked?

If this is occurring under towing, climbing, or hard acceleration there is a TSB regarding sticking valves in the affected cylinders. Solution appears to be increasing the valve stem clearance. Hope that is not the problem with your truck.

When the CEL is blinking it means that damage can be done to the catalytic converter so beware of continued operation in this condition.


#4

The misfiring occurs at idle, and whenever I’m driving it. It runs very roughly. You can feel the excessive vibration while you’re just sitting there. I have the 4.3 liter V6 for an engine.

I noticed it was idling a little funny last week - it normally idles at 500 RPMs. Every so often, it would drop a couple hundred RPMS and bounce back - nothing dramatic, but something I noticed.


#5

2001 gmc 4.3 v6 same problem word for word what did you find out because i just did the cap,rotor,plugs,and wiers still same thing


#6

Yeah, it ended up being fuel injectors.