Getting real frustrated with my H2. I have taken it to 4 shops now. 2 times to one dealership and 1 time to another. It is currently back at the transmission shop. The dealership techs are saying its the transmission and the transmission shop is saying its in the drive by wire.
No codes to read.
When you accelerate from 40mph or 60mph with a gradual acceleration the vehicle while bog until the point of downshifting. When on the highway it will not keep a constant speed of 60mph. When you try to speed up there is no gas until it downshifts. If anyone has had similar issues i would greatly appreciate any info on helping

 

Maybe start with basics like fuel filter/pump, things of that nature that are easily replaceable. It may be in a weird RPM/fuel demand point at that mph where a fuel pump going bad can't keep up.


I would think a dealership can easily check a harness for continuity. Matter of fact I know they can because my wife's 16 Camaro SS had a problem with the electronic parking brake, it was found to have a short midway through the harness and they made a jumper harness to fix the issue.

 

Thx for the reply,
I have gone through a alot of basics
New pedal position sensor
New Throttle control actuator
New Mass Air Sensor
New Air filter
New throttle body
New TPS sensor
Checked fuel pressure
New Plugs and wires. Not really needed
Everything installed has relearned
The dealership could not find anything because they dont look unless a code comes up. I hate to change the fuel pump and filter and not need it.
Its running around 50 to 55 at idle. 60 when i unplug the regulator and it drops down to around 45 to 50 when you trottle on it.
Ecm has not been send off yet. But not sure if that could be the problem either.
Terrible that the most reputable dealerships cannot diagnose the problem.

 

A few thoughts, make sure you don't have a plugged cat or exhaust. Semi easy way to test cats is after a good drive, carefully feel the cats and see if one is hotter than the other. They will be hot, but not screaming hot if that makes sense.

Take it to a shop or tuner that can read your timing. It might be a knock sensor that's bad causing the timing to retard. This might not throw a code if the voltage remains within spec but it could pull as much as -10 degrees of timing out which would account for all that you are talking about.

Also along the same lines, make sure nothing is loose, rattling or knocking around on the engine. This might send a false knock to the sensors. I had a friend have this happen because his exhaust would hit on the frame from time to time .

Good luck

Tim

 

Thanks for the reply
Yes i need to check the cats and maybe the knock sensor. i was thinking if the knock sensor was bad it would have a code or not run at all. My exhaust sounds a little louder than normal after sitting for 6 months.

 

Thx tharbar. i will definitely check all those things next. its still at the transmission shop. They are going to drive it today. if they dont find anything im going to tear into it this weekend.

 

I'd think you would get a code if one of the knock sensors was going, at least you should but as tharber said, if it still falls within spec it might not. Only a 2003 and I think maybe some 2004's have a separate replaceable fuel filter. Later models do not - you have to drop the fuel tank and replace the pump on later models. Cats are a definite possibility too but I'd think that would affect things at all ranges. Its like only at a certain fuel/air ratio in a rich band (somewhat low engine speed and adding fuel to increase power) is causing it to bog.

One thing for sure on our H2's is there is not nearly as much troubleshooting info from others online as there is for GM trucks. It can always be very helpful to google the same issue but put in Silverado 6.0 (or 6.2 if you have an 08/09 model) and you will almost always find a TON of GM truck owner forums and posts from those with trucks exhibiting the same symptoms. They have essentially the same drive train and there a whole lot more of the trucks on the road than Hummers.

 

I have replaced the fuel filter twice now and no change.
On a computer it looked as though my fuel lean was in the negative to zero readings. I really dont know the correct readings. i figured chevrolet would of caught that if it was a big problem. maybe not.

 

do you have a way to monitor the PID's to see what the timing is doing?

I would check the cats for sure.

Not sure what fuel lean is but if its the long and short term fuel trims than it should be at or near zero.

Neal

 

That's good info. You're referring to fuel trim being negative. Which means its running too rich..

Running too rich – High negative fuel trim corrections can be caused by MAF sensor problems, high fuel pressure, leaking fuel pressure regulator diaphragm, faulty evaporative emissions components, leaking injectors, defective O2 sensors, exhaust leaks/pinholes before the O2 sensor, coolant temp sensor problems, and base engine issues such as low compression and incorrect camshaft timing. In simple English, if the O2 sensors detect too much fuel, it will cut fuel pulses to the injectors to maintain the proper air to fuel ratio. When you accelerate, you need more fuel.

After you check the cats look and see if you have any loose or missing exhaust manifold bolts. This will throw off the o2 sensors too. I think you'll find something with the cats/O2 or knock sensors.

Tim