I am having a couple of problems with my '04 H2, and before I take it to the "stealer", I thought I would ask here first. I have had too many experiences with the dealer just playing hit or miss with my money.

Anyway, first issue. When driving between 45 & 50mph and rpm's around 1600 or so, there is a definite "surging" of a couple of hundred rpm. You can feel it and see it on the tach. If I accelerate up to maybe 55mph it goes away. I don't feel it at any other speed or rpm range. I have checked the trans fluid and it is right on the mark. It doesn't seem to matter if the truck has warmed up, or if it is cold.

Second problem. Lately I have been getting a check engine light. One of the codes refers to something with the heating and air system. Another has to do with the drivers seat, and the last one refers to checking the gas cap or a vacuum issue on the evaporative canister. I also have noticed that it can be troublesome to start after I get fuel. I apologize for not having the codes handy, I wrote them down and they are in the truck and it's snowing like crazy ATM and I am simply too warm and too lazy right now to run out and grab the paper out of the truck

I would like to check the evap canister. Can someone suggest what I should be looking for? Also, is it worthwhile tearing into the dash to fix the heater issue?

If I reset the codes, it might be a week or so of regular driving before they pop up again, then it may not be all the codes. Sometimes 1, sometimes all 3, but I have yet to get anything other than those.

Hopefully someone has seen these issues before and can put me on the right track to get this cleared up. I'm very happy with my H2 and would like to clear up these minor issues.

Thanks in advance for the help.

 

Check for any loose intake hose connections. I had a similar experience with the slight surging. Eventually the car would run rich and stall at idle. Check engine light came on (didn't pull code). After looking through the engine, I found a hose that had came off right before the throttle body. Mine is supercharged and it looked like part of the supercharger setup so you might not have the same hose setup but you probably have something loose.

 

If you fill your tank too full I've heard it damages your charcoal canister which is part of your evap system...you need to run a smoke machine through your system to see if there are any leaks...does it say small leak or large? The surging could me throttle position sensor but IDE start with a free step of cleaning your throttle body & checking your air filter & making sure there is no leaves obstructing your mass air flow sensor...

 

Usually when you get the code to check the gas cap, it wasn't put back on right. But since you have had problems after gassing several times now, I'd almost think it would be good to just replace the cap and see if that helps.
I've heard if the caps aren't sealed right, you can have problems. I'd think it would be more of a stretch to think the evap canister is them gremlin, though anything is possible.

 

Also check your transmission fluid easy to check and might be the cause of the surging as it is shifting.

 

I need the codes to even give you an educated opinion.... there is no other way other than guessing which one of the 117 things you could spend $38 to $1100 changing...

My surging and CEI was due to my knock sensors.... clearing the code let it go away for a few days.... surging due to the retarding of the timing...

The other major H2 evap item is the vent solenoid... although that was just a CEI and no other noticeable issue.