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hummer h3 low idle

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Sarah Koepp

Probationary Member
Messages
1
I just bought a 2006 h3. fell in love the minute I saw it. candy apple red and so much chrome you could see it from the moon! but....i have noticed that it idles down to about 600 rpm very breifly right before I come to a stop and then quickly recovers. I am reading too much stuff indicating that it could be from a defective cylinder?...someone help. Im freaking out. it has 69K on it.
 
alrock

alrock

El Diablo
Staff member
Messages
10,608
Location
Scottsdale
Welcome Sarah and congrats on your new ride! While I'd defer to Mike as he knows much more than I do I'd recommend a few things:
1) Run some Techron through the engine. It's available at auto parts stores, Costco, etc. Best engine/fuel system cleaner out there
2) Clean the throttle body. Easy job and we can walk you through it. May be some instructions on here in the Installations/Modifications area.
3) Get a compression test done on it as the symptoms could indicate a cylinder head issue which is unfortunately not uncommon and could be expensive. If it is that issue we may be able to arm you with some info to at least get the dealer or GM to shoulder some of the cost.

What part of the country are you located?

BTW, if you want to change your screen name (FB sign ups make you use your real name) then send me a PM with your desired screen name and I'll change it for you.
 
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hummech

Well-Known Member
Messages
123
Location
huntington beach ca.
hello Sarah, alrock is correct with the fuel additive and the biggest thing is the throttle body cleaning. what is happening is the vehicle has a idle air control which is part of the trottle body and when it gets dirty it gets slow to react to what the PCM is doing with it, it is more technical then that but tried to make it simple to understand for you.
on the good side, your head is most likely fine, when you have that issue, the check engine light comes on and will store codes for cylinder misfiring on random cylinders.
one other thing to do, and General Motors released a technical service bulletin for this issue is to use only top teir fuels in the Hummer H2 and the H3. we have seen a lot of issues when vehicles that are running lower teir fuel like rough idle, hesitation and poor throttle response and surging idle. some of the top teir fuel stations are cheveron, shell, 76 lower teir is moble,BP and arco.
let me know if you need any more info,
mike s.
 
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LagunaH1

Well-Known Member
Messages
3,726
Location
Idaho
X2 on what hummech said about using good gas. In my car, I stick to Chevron and if I can't get that, Shell. Only if I can't get either will I get some other brand. Some years ago I had a particularly finnicky car (not a Hummer) and Chevron was the ONLY gas the engine would run on without pinging / knocking.
 
cgalpha08

cgalpha08

"Like Nothing Else"
Messages
3,684
Location
Indianapolis, IN
Ethanol in gas is bad for an engine, so if you can find an ethanol free gas station, buy there! I am also experimenting with adding acetone to gas, i don't remember the amount off of the top of my head but its like 2-4 ounces for the whole tank. Its supposed to get rid of the problems that the ethanol does to your engine. I also run a thing of Lucas oil, tune up in a bottle, with every tank.

Sent from my DROID BIONIC using Tapatalk 2
 
alrock

alrock

El Diablo
Staff member
Messages
10,608
Location
Scottsdale
I've stopped using gas from Fry's/Kroger and most other low end stations. I don't notice a difference on the first tank (others might) but after 2-3 tanks of lower quality stuff vs. the good stuff there's a measurable difference. For me, I only use Chevron, Shell and Quik Trip.

Even in Moab I've stopped going to Maverik (wait, will that get me banned from the Banned and Damned) and generally only go to the Chevron.
 
alrock

alrock

El Diablo
Staff member
Messages
10,608
Location
Scottsdale
For me, just buying from those stations. I've never put anything higher than 87 in my truck. I still run Techron through the engine about once every three months as well.
 
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hummech

Well-Known Member
Messages
123
Location
huntington beach ca.
this is not about octain rating but the quality of the fuel. there are a few list out there with the top teir gas stations and lower teir ones. i would still service the throttle body on all the H2 and H3 vehicles though, we charge a pretty pennie to do them (IMO ) but all you need is a can of throttle cleaner from your local auto parts and remove the boot from the air cleaner to the intake/throttle body, remove it off the throttle body and open the butterfly plate and clean the throttle body. we use brushes on them at work. you would be surprised what a differance it make on the engine purformance, even if you don't notice a issue now.
mike s.
 
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hummech

Well-Known Member
Messages
123
Location
huntington beach ca.
all diesel #2 is bad and i recommend additives at least once a month on anything with a diesel. we got the Same memo from General Motors on diesel too but no recommendations as far as quality stations that sell up graded diesel.
 
Kurt

Kurt

Well-Known Member
Messages
958
Location
Orange County, CA
I run Diesel Kleen from the auto parts store, I throw quarter a bottle into my H1's 2 tanks every so often. I heard ATF is fine as well for lubricating the injection pump.

On that note I tend to buy diesel from places that replenish their diesel supply on a regular basis, vs a gas station that doesn't get much diesel sales and may only restock their big diesel tank every few months.

For the H1 the official AM General approved product is the Stanadyne additive...
 
Kurt

Kurt

Well-Known Member
Messages
958
Location
Orange County, CA
Back to low idle, will carbon build up in the EGR system cause this? If so what's the best procedure to clean this system out assuming the sensor and valve is operational?

Remove EGR, and clean with MAF/Choke cleaner and use a bit of pipe cleaner then reassemble with a new gasket?
 
deserth3

deserth3

Well-Known Member
Messages
1,073
Location
Conroe, TX
There's no EGR system in the I-5 engine.

This is part of a much longer article.
The Vortec 3.7L I5 carries over the VVT (variable valvetiming) or cam phasing system employed on the 3.5L I-5, which was one of theworld’s first truck engines with this technology. The cam phaser changesexhaust cam lobe timing relative to the cam-drive sprocket, which in turnvaries exhaust valve timing on the fly, maximizing engine performance for givendemands and conditions. At idle, for example, the exhaust cam is at the fulladvanced position for minimum intake-valve overlap. That allows exceptionallysmooth idling. Under other operating conditions, the phaser adjusts to deliveroptimal exhaust-valve timing for performance, drivability and fuel economy. Theresult is linear delivery of torque, with near-peak levels over a broad rpmrange, and high specific output (horsepower per liter of displacement) withoutsacrificing overall engine response or drivability. Because it manages valveoverlap at optimum levels, cam phasing also eliminates the need for an ExhaustGas Recirculation (EGR) system.
 
deserth3

deserth3

Well-Known Member
Messages
1,073
Location
Conroe, TX
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MaxPF

MaxPF

AGNTSA
Messages
1,394
Location
The dark side of the globe
LagunaH1 said:
On a side note: Are there similar differences in fuel quality when it comes to diesel?
Click to expand...

The current ULSD is crap - It doesn't matter where you get it. A guy over at the Diesel Place tested various additives strictly for best lubricity performance (cold weather performance can be addressed with other additives if needed). The winner was not what you would expect ;)

I should point out that this test has never been independently verified, so keep that in mind. Also, AMG recommends Stanadyne additives for a simple reason: the 6.2 and 6.5s use Stanadyne injector pumps. Stanadyne additives didn't fare well in these tests, but again I would like to see another set of tests to confirm these.

Go forth and read: http://www.johnfjensen.com/Diesel_fuel_additive_test.pdf
 
M22KLARS

M22KLARS

Unsafe At Any Speed
Messages
2,315
Location
Minnesota
Get a compression and leak down test done. I had the same symptoms and had major issues with Cyl #2. In my case was probably going on for a long time.
 
Hunner

Hunner

Well-Known Member
Messages
2,334
Location
Arkansas
Wife works for an oil distribution company and when they "pull" a tank truck full of gasoline off the pipeline at the bulk plant they indicate what brand they want and that formula of additives is blended as it is filled up. This also changes seasonally.
There are also what is called "independent labs" formulations where a brand is more in control from refinery to truck to distribution stations and some of those may be what is considered the lower tier fuels.
The diesel they sell has an additive they specify blended into it and I buy as much as 90 gallons of diesel at a time and it stays in my aux tank quite awhile sometimes, without problems.
There is a "cetane" additive you can add that seems to help some under hard pulling.
However I have just run a tank or so of bio-diesel in the Cummins and it smokes less but I have this urge to buy fries???
They have a plant down where I used to live on a farm and the local farmers have invested in this technology to use some of their soybean crops to run their equipment so I support my farmer friends and remember, "don't cuss a farmer with your mouth full."

I hope you get your idle problem solved. As usual we get a little diverse in our replies as it triggers other thoughts.
Mike gives us lots of good insight being in the mainstream of service.
Thanks to him, again.
 
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