Re: 99 z71 chevy spark knocking

I was wondering if anyone else has had this problem. After about 40,000
> miles I noticed a spark knocking noise (not very loud) at around 40 to 60 > MPH. It seems to do it only when going up a hill or pulling a load, It last > for about 3 to 4 mins then stops. > > After talking to MANY mechanics they pretty much all said, this is normal. > The timing is controlled by a computer, and can not be manually adjusted, > the computer lets the engine start to knock then adjust the timing.And they > are QUICK to add if the computer was not adjusting the timing so often, you > would get really bad gas mileage. > > OK..so is there a timing program version 2.0 that I need? :) > > Thanks for the help!! > Marty > >

Marty,

The mechanics are partially correct. The computer advances the spark until it detects knock, then IMMEDIATELY retards it to a safe level. By immediately I mean within 1 second, so fast you usually don't even HEAR the knock. I'd run a bottle or two of Chevron Techron thru yer' gas tank (1 bottle treats 12 gallons, so use accordingly) and change out the fuel filter as well. If that doesn't clear it up post back.

Doc

I have a 99 Z71 also, no problems with what you talk about

My son in-law works at a parts shop that has a Vehicle computer recalibration machine that's hooked up to GM

I went to the following website first to see if there were any updates for the computer in my truck and there was 3 pages of them, I couldn't believe it, the updates ranged from tranny shift to fuel mixture adjustments to pinging to idle problems etc

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Go to the website, enter the VIN # to your truck and it'll search GM's database to see if there are any updates for your vehicle, basically all that happens is the computer is taken out of your truck, hooked up to a computer, your VIN # and specifics are entered in, it basically reformats the computer on your truck and includes all the updates, they re-install your computer, hook another machine up to it, fire the truck up, then the truck engine thinks something is screwy, they do what they call a "case learn" so the crank can get back in sync with everything else, clear out all of the errors out, mine had lots, and done.

I didn't really notice any difference afterwards, I got it done for free, otherwise, I probably wouldn't have bothered if it was going to cost me.

It might be worth looking into for yours if its pinging

Brian

PS, This may be a Canadian site (if it makes a difference), I am from Canada