I don't know if the two problems are related but a few days ago while driving I got a lost of power . Truck keep running at low speed , barely enough to go over a small hill before going out of the highway ..
The display show . Power reduced
Temperature was normal as everything else
I give it 10 min then started again and all back to normal .
No problems since....

However before and after that happened . The engine shakes a little right before it comes to a full stop .
Iddle isn't smooth but neither to

My guess: TPC ... Dirty intake... Maf ... spark plug/wire

Any idea where to start

Btw ... not codes ... I got a check engine light when the power was reduced but it goes off when start after the 10 min

Thx

 

Another one to check that is biting me right now..... I do have a check engine light too. P0332 is the code. Its the stupid rear knock sensor. Google GM truck knock sensor... Its a very common issue on the LS engines. What got mine acting up is I cleaned the engine compartment. I was almost expecting it as I had to replace them on my GMC truck a couple of years ago.

Basically they are two sensors installed in the block right underneath the intake manifold.

So for knock sensors..... and you will probably need to replacement at some point, is you will want to get those, a new harness for them, and new intake manifold gaskets. And..... since you are pulling your intake manifold off you may as well go ahead and take care of some other things while you are at it like cleaning out the intake manifold, cleaning the throttle body, MAF, new valley pan gasket, change valve cover gaskets if yours are leaking (yet), new throttle body gasket, etc. Just some general tidying up and whatnot. Its a half a day job to do.

This of course might not have anything to do with the problem yours is having. If it is though the knock sensors going out can cause the issues you are seeing, big loss of fuel economy, stumbling, etc. The problem is GM installs these foam blocks under the front and rear edges of the intake. The foam degrades over time and water runs under the intake. Normally not a problem. However the knock sensors are down in two recessed holes and the wires go through a big rubber plug, much like the upper outside corner lights on our roofs. Well that rubber plug dries out and eventually water runs down into the recess and corrodes the connection on the knock sensors. Also if you do replace them ONLY get genuine AC Delco knock sensors. The cheap ones are well known to fail and last under a year and replacing them is not something you want to do often. The Dorman knock sensor harness is fine though and has new plugs. GM suggests building an RTV dam around the rear one to channel water away from its grommet. Most people RTV the entire perimeter of the grommet.


Aside from that it could be a dozen other things. Fuel delivery problems - fuel pump, filter/strainer, pressure regulator, injectors, bad gas. Spark problems - plugs, wires, coils. Air problems - vacuum leaks, PCV, MAP, MAF, catalytic converters getting clogged. Sensor/electrical problems - MAF, MAP, O2 sensors. Really need to pull codes and see what code set that check engine light.

 

WOW By the list I better take a vacation month to take care of all that .. LOL

Unfortunately I didn't have a code reader at the moment it throw the codes ..
Im going to start a due maintenance such as plugs/wires etc and see what comes next

THX

 

I would also assume a knock sensor. They seem to cause havoc when they start acting up. There are threads around the H2 forums on how to replace them and how to seal them so water doesn't cause issues down the road.

 

I will look for the info.. due to the prone to fail it seems like a due maintenance anyway

Man I love love this truck and plan to keep it 4ever but Idoubt I will buy another American vehicle ever ... there is always something

 

Knock sensor replacement - Hummer Forums by Elcova

 

Its not just american cars....... Every brand has their own sets of common issues. Wife has an Inifiti FX35 which is a total piece of junk in comparison to my H2 and the FX is 3 years newer and has less miles. Tons of electrical problems, transmission problems, AC clutch, brake rotors all warped, burns about a quart of oil every 500 miles, and more. She had a BMW X5 and also had issues, nothing like the Inifiniti.


The knock sensors. Yeah - I'm getting my parts figured out and ordered this week. When I did them on my truck I realized how bad the buildup was in the intake and ended up leaving it torn down for an extra week while I cleaned the gunk out of that. This time - I picked up a used intake manifold on Craigslist this past weekend for $40 that I'll get all cleaned out ahead of time. I know one of my rocker covers are leaking so I'm going to replace those gaskets while I'm at it as well as the valley cover gasket / knock sensor hole seals.

 

Flyday Thank you for the link .. It looks like a very fun DIY . Im waiting till engine light throw some codes . Really I dont want to take the whole intake out for nothing ... I dont play in water too often .. Other than road rain ponds


MixManSC ... Man I agree any car could turn into a lemon .. But after 5 or 6 american cars/trucks it is proved , after 100k all american cars are lemons

Ive got a Honda element with 140k . Drive at least 100 miles daily carrying around 500 pnds and only issue has been the shocks and alternator
My dad has a 98 toyota and after 120k only issue was the AC compr
My Mom in law drive a honda and not issues with 97k

With the Hummer I've been fixing things since the 80k including big fixes such as main rear seal and small things such as a stupid plastic holding the whole transmission shift system

Not discussion here but American vehicles arent made to last more than 100k

Still I love the Hummer and never regret to buy it , much less to fix it and never thik of selling

 

You need to rent or buy a code scanner/reader to find out exactly WHY your CEL is on then goes off. usually in those circumstances its an emissions problem but its all guess work unless you know WHY the CEL went on.

 

I have the scanner . But not code is stored. Btw the problem started before the engine power reduced issue
Will check a few things over the weekend