Hi guys I have a 2006 GMC 1500 4x4 just under 100,000 miles on a GM crate engine, 266,000 on truck, runs great no loss of power, no drop in MPG. sill get 17-18 around town on 87. If I put 90-91 gas in when pulling a load I get 18 all day long. So were is the problem? I am getting spark knock. I have tried diffrent gas, just put in plugs and wires. Old plugs looked good. No Cel on, No codes. It happens when I am flat roads and going up hills. I did get to go away for 1 tank when I switched gas stations,but now all brands of gas do it. This has been going for 3 mo’s. One more thing it all started after I made a 800 mile round trip puling a trailer ( just under 5000 lbs on trailer 2 axle enclosed). On that trip as always do I used 90-91 gas. Any ideas?
I suggest retrieving fault codes
I’ve replaced quite a few knock sensors on GM V8s just like yours
I was thinking it may be the knock sensor too. With no codes I did not want to run out and buy one. I will see if I can pull any fault codes. I took it before to my buddy’s shop and could not get any codes to come up. Thanks
I would suspect an EGR system fault.