2008 Hummer H3 Hummer H3 Engine Knock/Pinging

C3 ROLLING

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2008 HUMMER H3

Engine Mechanical problem
2008 Hummer H3 Four Wheel Drive Automatic 26,000 miles

My 2008 Hummer H3 is having a problem with moderate pinging under load. It occurs heavily when the engine is hot and the A/C is on and I'm driving up hill. The pinging will continue and never stop. I can feel the vehicle losing power and feeling sluggish, probably due to timing being pulled to the max. Ive taken it to 2 different Hummer dealers and they acknowledge that its pinging but say their tests show that there is nothing wrong with the vehicle. The H3 is recommended at 87 octane but I have to use 91 octane to keep it from knocking. Ive tried changing the plugs, cleaned the MAF, changed the air filter, flushed radiator, changed to synthetic oil, run several treatments of engine/fuel cleaners with no results. Ive never abused the motor and only fueled up with top tier fuel brands.

5 Replies

MHPAUTOS

MECHANIC
31,938 POSTS

Hi there,

Thank you for the donation,

I would be thinking that the knock sensor may be faulty, I would think that it would pull a code if it was at fault, has this been check? It may not give a check engine light either, also you may be able to test it by hooking up a scanner with live data read out, with the engine running, tap the block near the sensor with a ball pean hammer, this should induce a response for the crystal in the sensor and watching the live data read out you should see a minor timing adjustment, I have do this with a Holden (local Aussie make) with good results to locate a faulty knock sensor, it may be worth a try.

Mark (mhpautos)

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Friday, October 23rd, 2009 AT 4:47 AM

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The dealerships have already tested the knock sensors and said they are functioning perfectly. They said that its probably continuing to knock because the computer can only pull a certain amount of timing. Both dealers said there scan tests showed no malfunctions.

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Friday, October 23rd, 2009 AT 10:19 AM

MHPAUTOS

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Is this something that has just started to be a problem, or has it done it for some time, and has the head been off by chance?

Mark (mhpautos)

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Friday, October 23rd, 2009 AT 10:44 PM

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Its been a problem for over 10,000 miles since I first noticed it. I bought my H3 in the winter so the weather was cool and I never ran the A/C. When summer hit and I started running the A/C, thats when I first heard the popping/pinging noises under load. It doesnt occur when I run 91 octane but it will still ping with 89 octane. Ive never had any engine work done and the head has never been removed. I used to run a K&N air filter but the dealer said that may be the problem so I removed it but the ping hasn't reduced. Ive cleaned the MAF with the MAF cleaner and that didnt work. I run probably about 50 dollars worth of fuel system/carbon cleaner with no results. Both dealers insist the vehicle is running perfectly according to the scanners. I also have a ODBII scanner and the H3 isnt overheating, usually around 191 degrees on the coolant temp. Checked all spark plugs and they look fine. This is very frustrating because the H3 is only a year old and has been well taken care of.

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Friday, October 23rd, 2009 AT 11:13 PM

MHPAUTOS

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Hi there,

This is very frustrating as with out getting my hands on it in am limited with what I can do, I must be guided by what your dealers tell you, so if the knock sensors are working I can only put it down to compression ratio, but as the head has never been off this really rules out an incorrect thickness head gasket, I would like to know if the base timing setting is correct, did they check that with the live data stream? And can they get a print out of the timing curve with there scanner? This may shed some light on the problem, failing this I would be saying it is an octane rating of the fuel that is causing this, ask a few of these questions of your dealer and see what they come up with.

Mark (mhpautos)