Anybody good at diagnosing data logs??

[Seer]

right, thats why i asked if he thought every misfire would cause a large enough change in RPM to dictate a misfire CODE.

i work on a TON of GM trucks/suv's with the LS motors. notorious for vacuum leaks at the intake gaskets, and will show constant misfires at idle on any scanner, but will never set a code. thats all i'm saying is there is always instances of problems that dont set a code, even misfires. however that might not be true with the 5.0 as i have no experience with it yet.

i'm not arguing that his car is misfiring or not, i'm simply saying no code doesnt mean no problem on ANY vehicle.

Also keep in mind the TiVCT/cam profiles also makes these cars sound a little rough and lopey at idle. Nothing near a performance cam though.

 

[DGRacing]

I'm going to say there is perhaps more than one thing happening here.

- I still think a more thorough vacuum check is needed. I found my passenger oil catch can hose was cracked after hearing lots of random knocks and blurps in my idle (from the exhaust). Replaced the can/hose and idles smooth now.

- There can also be a bad sensor somewhere (e.g. crankshaft position sensor failing periodically) in the ignition system causing a near-misfire that dodges the CEL. A dealer can do an ignition diagnostic to check all the sensor levels, voltages, etc.

 

[slvr08gt]

I'm going to say there is perhaps more than one thing happening here.

- I still think a more thorough vacuum check is needed. I found my passenger oil catch can hose was cracked after hearing lots of random knocks and blurps in my idle (from the exhaust). Replaced the can/hose and idles smooth now.

- There can also be a bad sensor somewhere (e.g. crankshaft position sensor failing periodically) in the ignition system causing a near-misfire that dodges the CEL. A dealer can do an ignition diagnostic to check all the sensor levels, voltages, etc.

Wish I knew how to narrow it down also. Not getting any support from any of the three local dealers here either.

Either way the car will be sold in a couple months and I will be moving on to a different platform. IMHO after owning four 5.0's, they just have too many little issues that rattle my OCD. Maybe ive just had bad luck with the manuals, the two autos I owned were solid performers but boring as hell to DD.