There is an engine noise ( not exclusive to the H3) when towing up a hill and you have to really step on the gas. At a certain throttle I start to hear a knocking/rattle from the engine. If I back off just a hair on the gas the noise goes away. I have heard this in other trucks I have had when towing or hauling a heavy load. What is it? Is it the valves rattling due to the heavy load or ???? Is it bad for the engine to keep it at this throttle level? My gut says its not a good thing...?

Its not just a H3 thing but a general engine thing. Any ideas??

 

A heavy load and low octane fuel can sometimes result in knocking/detonation. New engines have, among other things, a knock sensor and should counter by a PCM adjustment, or throw a code. I will say that when the VVT changes (in part) to counter detonation, it does sound noticeably different, so maybe that is what you are hearing? No lights or codes, you should be ok.

 

Hey Doc,

I am familiar with the low octane knocking phenomenom, but when I am towing my trailer I always fill up with premium gas ( 91-92 octane ). The noise I hear is a not a heavy knock, but a very light knock, almost a "ting" or rattle thats in sync with the engine. Theres no codes or lights, I just get the impression I am asking too much of the engine at that load and throttle level. If I let off the gas 2 mm's the noise will stop,the threshold for hearing the noise is that sensitive.

My gut tells me when I hear that noise I shouldn't give it more gas and just crusie at whatever speed I am at. As long as I'm not stressing the engine I'll feel OK.Hopefully I'm doing the right thing.

6 months left on my lease and since I tow a trailer now the Alpha is sounding pretty good.

 

If the simple solution is the answer then it might just be that at those high revs, its vibrating quickly and harmonizing heat shields, covers and things like exhaust.

..or you might just happened to be above the sound frequency in terms of tone where the GM engineers decided they didn't have to block ambient sound anymore.

 

I hear your point...the rpm's are relatively low/ mid range.. its more of a strain on the engine sound...as an 06'er I think I have dealt with it all ( not proud of it [&:]) I went thru the whole song and dance with the heat shield, head valve issue, steering shaft, and a slew of other minor things. My gut says its a strain on the engine, but I AM NO EXPERT IN THIS FIELD, SO I VALUE ALL YOUR INPUTS.

I just want to be sure when I hear the sound and I back off the throttle I am doing the right thing, if I can stay on the gas and not do harm to the enigne than I would like to do that.

Thanks for input and any more is appreciated.

BTW. When I say heavy load I am talking about a 38-4000 lbs trailer.