Tow Rig ??????

[DansBlown73Nordic]

I have a 98 GMC 1 ton dually 4x4. It has the 350.The problem is it pings all the time. I can put good gas in it and it still pings.
Today I changed the knock sensor. It did nothing. :mad:
So anybody got any ideas??? It has this huge warning on the inner fender that Says " Do Not Move The Distributer" Timing is set by the computer. Im afraid the motor is going to launch next.... cry

[1stepcloser]

Make sure the EGR system is functioing properly.

[Kindsvater Flat]

Knock sensor or wiring to it is broken. It will retard the timing if it pings.

[fixit1002]

howdy guys well very doughtfull broken wire eng light would be on this truck is obd2 second generation so first are you sure its ping and not piston slap chevy has had problems with no piston skirt so they tend to slap also there was a voluntary recall for this prob but diffrent motor i think it sounds like it may need to be reprogramed call chevy and ask about any updates for this prob they may or maynot be helpfull dealers tend to suck when you ask something technical the timing is controlled by the ecm if you turn the distributor you will!!!! knock the cam sensor out and turn on the service soon light.you need a scan tool and go drive it while looking at the readings for knock retard.egr is also controlled by ecm and if no function will also turn on srvice soon light it is possable to be fuel filter or mass air flow sensor may be dirty clean with good electrical parts cleaner lean run will cause knock but to lean again will set on light well sorry for long post let me know ken

[DansBlown73Nordic]

Im am 100% sure its spark knock. It use to only do it if I was towing. I would just use good gas and it was ok. Now it does it all the time even with 94 octane. I have a pretty good dealer that I use to work at a few years ago. I will call and see if they will give me any info.
The reader for the ECM? Would a Snap-On tool that plugs in read the map sensing and the timing stuff? I know it tells engine temp and a bunch of other info.