99Silver6.0

iTrader: (1)

Just recently when driving, running about 45MPH while not in overdrive If I lay into the gas ever so slightly and I am really quiet and the radio is off I can hear a little knock. I installed 2 10K ohm resistors in line with my knock sensors because I was getting alot of false knock. I ran a tank of 100 ocane just to check that it was in fact false knock. The KR still existed while running 100. So my question is this. Why on stock 99 timing tables am I hearing a bit of knock at low RPM's?? Do I need to take 1-2* from the 1000-2500RPM range in the high octane table??

LOW2000

1000rpm at 45mph is OD right? Thats when the load on your engine is going to be greatest, hence the detonation.

BigTex

iTrader: (16)

A good cleaning with GM Top Engine cleaner or Sea Foam would be a good idea. My previous truck had the same issue under OD load (it was a 99 too). Have you done anything to the EGR system?

ACDenali

iTrader: (8)

BigTex, how is that done? My truck idles low again and I dont want to take it to the dealer to let them clean whatever is needed to cure it and charge me $50.

99Silver6.0

iTrader: (1)

The knock is heard while the truck is not in OD. Only thing I have done to the EGR system is the tube cutdown. How do I go about cleaning the top end anyways?

BigTex

iTrader: (16)

Do a search for top end cleaner. Its basically a spray can of foamy solvent. You spray it slowly into the intake (not MAF) and let it clean the TB, intake, heads and chambers while the engine is running. Its purpose it to cut down on the carbon deposits that build up in the engine and help to reduce that part throttle pinging. You'll see alot od smoke from the exhaust and know its working.

Jorday

That stuff does work really nice. I use it once in a while on my car to keep in clean in there.

LOW2000

If you have never used it, dump in a bottle of chevron techron or gumout regane, you might just have a nasty deposit in one or more of your combustion chambers that is glowing causing the preignition.

BenKey

iTrader: (1)

I just used GM top cleaner last week. What the dealership does, as they explained it, is hook the can up to the fuel rail, or disconnect a vacuum line and suck it up through it. It was recommended by them for me to just run through my gas tank. I put it in with about 5gal left in my tank.

LS1csherm

The top engine cleaner works great -
It make a great smoke show
Shake the can well - put a piece of vac tubing in the can
and connect to a vacume port in the intake.
Start the truck and keep the rpm at 2k
when half empty - shut the truck off and let it soak.
then start the truck up again....
Then start the smoke show....
Directions are on the can...works great .