Noisy LLY

craneman03

craneman03

wet behind the ears
Joined
Feb 3, 2009
Messages
107
Anyone else ever experience what I would call a fuel knock out of there LLY? Seemed to notice first when I pulled my camper the other day. When it happens usually an rpm increase or decrease gets rid of the noise. No visible smoke and truck seems to run just fine. Just didn't seem to hear this when I first got the truck. Harness by the alternator is taped up and has a new loom around it. Should I be concerned or is this rattle typical?
 
Running any kind of tune when it did it?? What ECT on truck and ambient temp as well?? Smoke out tailpipe?? Any way to check balance rates??
 
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No smoke that I noticed. Ect was anywhere between 160 and up. I've got it to do it a few times at different temps. No tune in the truck. That's why I'm a little skiddish though, cuz I'm looking at going with a efi live or ppe tuner and I don't want anything wrong with the truck. I have no way of checking balance rates at this time.
 
Without more info, best I could suggest is an injector sticking. Either a ppe or v2 will let you see balance rates, at least give you an idea if you have a sick injector(s).

I used to get that knock on cold days when the truck had a quadzilla in it. Timing issue with ambient temps in the 20*F range. However, it cleared up once the truck warmed up. With efi tuning, i never had that issue.
 
Your edge insight will read injector balance rates. I had heard anything below/above +/- 4 is considered bad by GM techs. Just remember when you check them it doesn't always mean just that particular injector is bad it could be multiples or the firing mate of the one which is reading bad. For example maybe #8 is reading -11 and pulling fuel to make up for a bad #1 injector. I could be completely wrong this is just my understanding. Anyway, check your edge or see a tech that can shut down individual injectors to test which are bad.

EDIT: Does it do it when the motor is cold?
 
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Were you driving around 80-85 mph? Or above 2500 rims? Sounds like you are hearing the pilot injection or lack of. I can never remember which way.
 
X2 on how many rpms you hear it at. Pilot shuts off at 2400 iirc and that will cause the motor to get real noisy.
 
I've been working so its been a couple days, but when I really noticed it was when I was pulling my camper home the other day. It would start to get noisy around 2000 rpms on acceleration. Nothing serious but puts you in the mind of a fuel knock per say. Once up to speed cruising its quiet like normal. Truck runs fine, no smoke seems to have normal power.
 
:for llydmax:
I drove 45 minutes the other day to pick up my camper. We were only there 15-20 minutes so the motor was good and warm. Seemed to do it most of the way home.
 
Well to be honest I'm not sure. I have been at work working 12hr shifts in the mill. It will probably be Thursday or Friday before I get to it. Do you just go in through the menu to check the balance rates or what's the procedure?
 
I drove the truck to work today and heard the noise again. This time I was driving about 50mph and just eased into the throttle. It sounds exactly like spark knock. It's not the pilot injection changing to main injection, I've ruled that out. The first time I pulled the camper to drop it off for warranty work the truck ran flawlessly, no noises. The day I went to pick it up, put about 3/4 tank of fuel from a local Speedway, truck has had the knock ever since. Bad fuel?
 
i noticed mine will do the same thing sometimes when i run at the same rpm for a while, usually when i have the cruise on or under light throttle
 
dirty_max said:
i noticed mine will do the same thing sometimes when i run at the same rpm for a while, usually when i have the cruise on or under light throttle
Click to expand...

Sounds like youre in the same place you were last week. If it was bad fuel go buy a bottle of diesel kleen.. I really cant diagnose your truck over the internet and I'm sure others cant either. If its a sticky injector run kleen through it. Other than that get it scanned
 
Well the reason I was in the same place was because I had to work 7 straight 12 hour days at the mill from 9am-9pm. Doesn't leave a whole lot of free time to get it scanned now does it? So the next best thing was to get on here and get opinions. Never wanted you to diagnose my truck, but do like opinions and advice.
 
Checked my injector balance rates with a scanner today and everything seemed okay. At idle they were between +2.2/-2.5, in gear the were about the same with one being +2.9. They all looked good. After I ran the conditioner through it and got diesel at my normal place, it seems fine.
 
Could be one of many things.Running Diesel Kleen or Power Service through it won't hurt it,and for something that sporadic, it may help/fix the problem.

I used to have one injector get really high negative balance rates if I hammered on the truck for a while, making it idle rough. Ran PS every tank for a couple thousand miles, problem never came back, no matter how hard I pushed it.
 
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