Spark Knock - Vortec 6000

[Denaliano]

Hi guys - 2002 Sierra Denali LQ4 - I have a V1, I use it to see what's going on, scan and clear codes. Haven't upgraded to tune yet because prior I had gotten a Westers 91/93 tune. It's been a great tune, the truck has really come alive, but I have some serious spark knock around 4K, say while accelerating up an onramp to the interstate. I always run Mobil Super 93 and my MAF and TB is immaculately clean.

Attached is a log file from this morning, maybe someone could give some insight before I send my PCM back to Westers.

And maybe for Christmas, I can convince the GF to buy me the upgrade to Flashscan Commercial :)

[cmitchell17]

Im not on the right computer to look at your log, but have you looked into burst knock?

The burst knock I don't think should show in the KR.pid. But I had the same happen to me with my 2000 5.3 in second gear around 4000 it would knock like 3-5degrees. I zeroed out all the burst knock tables and that fixed it.

Burst knock is supposed to fix knock retard but it looks like its causing it according to the scanner.

[wait4me]

Looks like he is just commanding way too much timing for your engine.

The pcm is trying to apply over 35 degrees at wot. obviously it dont like it so it is pulling 7.7 degrees and only making it have 26 to 27 degrees at wot at that 4000 rpm point.

You need to send the pcm back to him and just have him back down the timing.

[Denaliano]

Thanks for the replies! My tuner asked me to check fuel pressure... which I did and it's at 58lbs with the pump commanded on.

Don't know how i'm going to do this, but it was suggested to monitor fuel pressure at WOT.

Ideas?

[Rhino79]

Anything over 28-29* at WOT is rediculous for a stock LS motor, I would have him shoot for 26-28*.

[Denaliano]

I found a redneck solution to monitor my fuel pressure at WOT - http://www.youtube.com/watch?v=y-Byc64NhVA

Looked normal to me. I'm sending the PCM back so he can shave off a few degrees. Thanks guys! :shake:

[Denaliano]

Ok guys, if anyone could take another peek at this new log file I made with my STOCK pcm - maybe share some ideas as to what's up. I'm still getting KR at WOT, and my injector duty cycles are high. MAP seems high. This is a stock LQ4 with only a K&N.

[Denaliano]

Getting 12.1inHg at idle in drive, 29.2inHg at WOT.

Normal?

I need to find out if this is feeding my PCM correct information - I'm being told that it may be faulty, leading to my spark knock situation.

I'd replace it without hesitation, but it's a $100+ little sensor.

[cmitchell17]

Do you hear anything when you open it up?

Next time you run it cut off the radio and everything and roll the windows up and listen.

The fact that the KR goes up to 4 degrees the fades away makes it look like false knock usally the KR line would have spikes in it.

My MAP will be at 100 at WOT with about a 100-101BARO, but it will fade down the about 95-96 after 4000rpm. I wonder why yours dosent but yours is a 6.0 and mines a 5.3.

Was that run in first or second?

[58Sleeper]

Looking at the first log i noticed the ECT around 194 degrees. In my experience a 160-180 degree thermostat will alow the engine to run cooler and allow you to run up to 25 to 26 degrees of timing without KR.(with the proper AFR) I have found that over 27 degrees of timing is hard to pull of with these LS motors without detonation. The commanded AFR in power enrichment at WOT looks a little rich but that would not result in detonation. If you look at frame 29 of your first log you will see TPS of around 76% and the commanded AFR is at 14.73. (That could cause detonation and -KR) I would rather see around 13.2 at that TPS. Frame 30 in the first log appears to be a gear change (1-2) that occured under the same TPS and as soon as the engine was loaded by the gear change it KR'd 12 degrees of timing. I think the culprit is high ECT and lean fuel due to the set up of the PE table. It's tough to make tuning changes via the internet.:notacrook:

[Denaliano]

:master: Wow, great information!

I wish there was an AWD Dyno available in my area so I could really fine tune my truck.

This hit and miss game is getting annoying!

[58Sleeper]

The thing to do is press the GF to make the upgrade and you'll be set. Meanwhile i would get the tune modified or just stay away from any scenario that causes detonation until you can make the tuning changes yourself.:rockon: