Hummer Trouble - Engine Misfire
 

So I was driving my H3 2007 (50k on it) today and I started feeling that the gas intake is breaking up (like an engine misifire). I stopped the car tightened the gas cap, turned it on again and drove more then saw the engine light flashing, later turned off, then flashed and stayed on.

I dropped it by a mechanic near my house to scan it tomorrow to see what's going on but the weird part is that it happened RIGHT after I put gas in it this morning (from MOBIL and not a crappy station) after it was empty.

had bad experiences with mechanics around me, so do you know what am I looking at in my case?

Hmmm... George, have you been driving it regularly? Chances of water in the gas line? Did you clean the air filter last time? Any other service done since cleaning the MAF/TB?

maybe bad O2 sensor

I have been driving it regularly since we fixed it a few weeks ago and it's been running GREAT! till today.. I cleaned the filter since it was a K&N (with the appropriate kit) and to be honest was slacking on the rest of the fluid&oil change till two days ago when I got the CHANGE OIL sign on the dashboard I realized alright that it's time to change it. It actually happened while driving to the mechanic (ironically) so left it there.

Water in the gas line?? how bad is that?

PS: mechanic asked me what oil to put I said Synthetic (I have no idea what they had in it) but I thought that would be better although it has only 50k on it.
Also mechanic didn't recommend flushing the transmission or any other work but the oil , since it only has 50k on it

It's a Po300 random misfire, mechanic seemed confused so I took it to the dealership for a diagnosis ($105) maybe I can pinpoint the issue as te possibilities are endless

So they r the spark plugs that another mechanic installed 2 weeks ago. Looks like he put the cheap kind. I hope he will do the job for free

Most any plug except OEM has given people problems. Doc Olds has stated a few options in the past but its easier for me to remember OEM. If you go with a different plug use the "search" function I'm sure you will find it.

Which brand are the oem spark plugs for the h3?

Yep, the I5s don't like aftermarket plugs for some reason. Since the OEM plugs are said to be good for 100K, I would stick with them.

Alright so new spark plug installed and fuel Injector cleaner just in case there was dirt in the gas tank and fuel Injection system. Test driving it the next two days to see before taking it on a long trip to Vermont so hope doesnt bug me there.

Btw Dan I am noticing that the rough idling on neutral is coming back slowly , could it be that I didn't clean up the TBD well?