KR at upper RPM

[Mikz86ta]

I had tried with both a modified Spark Adv and the stock one for the record.
I have some KR approaching the 4000 RPM range in the .60-up gm/cyl area. With both.
I noticed this during a KR and Spark log I typically run....and when I was getting on the interstate. So I was in like 3rd gear pull. Did also from a stop running up thru the gears.
Anyone else have this with their 4.3 ?
Spark Tables in the mid 20* range and it pulls down to high teens in KR. Pulling like close to 7* and below in this area.

[joecar]

I don't have a 4.3L...

But..

Can you verify that it is real knock and not some valvetrain noise...

Can you hear it knock using a Chassis Ear...?

[Mikz86ta]

I dont have a Chassis Ear :(

[nevinsb]

Those timing chains are notorious for getting loose too.

[Mikz86ta]

My exh is not quiet when you are getting on it (Edel headers and y-pipe, no cat, Hooker SuperComp and dump before axle) but I dont hear any audible pinging.


Side note..today I had some time, so I changed my AFR for e10 from what I was using 14.22 to 14.42. Thought maybe 14.2 was a bit rich and our gas is 'up to 10% eth' according to the stations. So stock was 14.68 on my truck. I figured I would bring it up a notch since my best milage has been 16.2 and I was getting 16.5 beofre. However, maybe I was getting better because of the 'winter' fuel blend. Now summer is here we have 'summer' blend. So could be that was the difference in my economy going down some?

After I reflashed the PE Ratio change and Commanded AFR change, I noticed while I was idleing in neutral, my AFR went very lean (17's). Gave throttle and came back up, but went lean for a minute after let off. Drove fine and AFR was toggleing as usual. PE came on as usual. But when I pulled to a stop and idled, it went lean again. Did it 2 more times after a drive and coming to a stop. Is that normal until it relearns to go so lean when coming to a stop after a drive. After a minute it goes back into normal idle afr :( weird

[joecar]

Is there some listening device you can rig up (hose) to listen while driving...?

It might just been noise...

Avoid going lean.

[Mikz86ta]

Yea it could be just normal 4.3 noise. I recall hearing about it years ago. However dont recall what rpm its normal at.
I do know over the years they have done stuff to reduce noise in the 4.3 (balance shaft, roller cam/lifters, roller rockers, a guide on the timing chain, aluminum oil pan, etc.) Mine is a 2003 which has all that. Plus I have aftermarket Comp Pro Mag 1.52 full roller rockers. Then again I may want to pull a cover and check to see if one has come loose. Tho with arp rocker studs and locking nuts, its not likely.

Yea the lean when return to idle after this last flash is a concern. IIRC tho I remember there is some of the 07-up LSx's that have a certain issue (dont recall exactly) that takes a few drives to correct itself. Seems like thats a ETC and IAT idle corelation

[slows10]

Have you installed the GM chain tensioner kit in your 4.3 yet? Its available at the dealer or other places. It is a tsb from gm for the 4.3 . It does help if you have a chain rattle. Edit I see now you said a chain guide is installed as well.

[Mikz86ta]

IIRC 2003 had it from the factory. Or am I mistaken?

[slows10]

Im not sure when they installed them from the factory. I know my old 97 4.3 didnt have one and probably should have.

[Mikz86ta]

I agree :)

[Mikz86ta]

So lets say it is false knock from someting else......can one play with the Knock Filter settings or just change/reduce the Burst Knock or total KR setting?

[joecar]

So lets say it is false knock from someting else......can one play with the Knock Filter settings or just change/reduce the Burst Knock or total KR setting?Yes, you could do that...

an oscilloscope with FFT feature would help in comparing plain noise vs knock, that would then help you figure out how to set the knock filter frequency.

[Mikz86ta]

Hmm, so not having that tool I would assume not to do anyting with those? Or is there a certain direction to go. Mine is at 2.50 and below is my options. Unclear which direction the filter works. Like dealing with the idle screw on Holley carbs....most are 'turn out' to add and some other models are opposite. Kinda helps to know which direction is what

The noise filter for the knock sensors.
This provides further filtering of noise from the knock sensor.

Only the following values may be entered into this table:
- 1.65
- 2.50
- 4.70
- 7.90

[Wheelz]

Subscribing. Been wondering the same

[Mikz86ta]

I also heard someone say (and I see on a few custom tunes) that IAT Spark table needs smooting and takes away too much timing.

[slows10]

Looks like your way lean when you enter pe. Your commanding 12:1 or so and getting 14:1 and higher. Maybe the ve and maf need more adjustment.

[Mikz86ta]

I see. I will need to check that :) thx

[joecar]

There are some cheap PC based oscilloscopes that will work for automotive stuff.