Have a friends truck 5.3 with Hot Cam and no other mods except CAT back exhaust. On the dyno (loading) start pulling at 2K and get to 2200 and start getting KR as high as 8 degrees total timing at 18 by 3900 and the Manifold pressure is 98Kpa. Truck only makes 195 to wheels. Anyone got any ideas whats going on with this thing?

Ardie

 

I think the pre-2000 PCM's had problems with over sensative Knock Sensing. You mention CAT Back exhaust, If it is hitting/vibrating anything this will transmit back to engine and seen as Knock. Bad Gas?

 

It's an 04 with only 126 miles on it. I don't know why it's seeing knock, I can't hear any and the AFR is 11.9 WOT. It runs like it's only at 18 degrees too!

 

Just re-read the post. I am kind of out of my league here... but I've also read that aggressive cams lobes can also trigger knock due to the valves slamming. Hopefully someone else will chime in.

 

Not sure if it shows up as knock, it didnt for me, but it sets a misfire code.

 

I have false KR (I think ) its below 2200 Rpms so I just turned my Knock sensors off intill 2400 Rpms. You might want to try that to see if it fixes the problem. If it knocks you will hear it. Kr sounds like a fast ticking noise. Well good luck I'm sure it only needs alittle tuning.

lator

Yellow

 

try useing 93 octane gas

 

better gas, check for things hitting the frame, etc. while running. something not put together correctly? a "cam" won't be a source of knock either, unless there is somthing wrong.

 

I did not install the cam, I wish I had. I did talk to the dealership that installed the cam and the mechanic said he lined up the dots on the cam and crank gears at TDC. I have tuned the hell out of the idle and it's nice and steady @ 650 RPM's with or without A/C. The truck is brand new and nothing is hitting anything on the frame or making any loud noises. I have done the tuning on the dyno and can hear anything going on since there is no road noise involved. Oh well, the truck will be back Monday and I'll work some more on it. Thanks for all the input guys.

Ardie.

 

Oh, and the dumb stuff has been checked, ie 93 octane etc......