5.3 fuel trims and knock

[LS ROB]

attached is a log i did today and am very surprised at what i found. This is my daily driver. I have always thought it seemed somewhat weak. Could low grade gas be the culprit of the knock? Also, is it normal for fuel trims to be off like this? As far as i know, there has never been anything done to the engine. This is a stock 2008 silverado 5.3. the MAF curve seems to go up so far and flat line. Am i expecting too much from a stock engine or is the fueling off on this thing? truck log1.hpl08 silverado-mine.hpt

[5FDP]

Fuel trims don't look off at all to me. Completely normal if you ask me. Seeing ~5% of zero on a stock truck with fuel that ranges from 5-10% alcohol content looks fine to me. I don't even worry one bit because the short term trims can more than account for that.

Having DoD on can cause part throttle knock to be shown, I see that alot. Also the knock sensors are pretty sensitive on some of these calibrations.

Just doing some PE changes and engine side TM change can wake up when you floor it though.

[LS ROB]

ok, good to hear that. Thank you. So, i just want to make sure i understand. Anything from -5% to +5% is normal? As for the PE changes, its set at 87. Do you suggest lowering that number? Also, where in the TM tables would you suggest changing?

[04silverado6.0]

For pe enable I've had good luck keeping mpg set at 65% throttle. Also get rid of the rpm delay by lowering the rpm to under 2000 and setting the timer to 0, set enrichment ramp in to 1. You could try lowering the gas eq ratio to 1.17 or 1.19.

[LS ROB]

i may give that a go! thank you!