Need help with Knock Retard

[Paul69camaro]

I've been chasing this KR for a few months now and I'm all out of ideas. I'm pretty confident its false but I'm hoping some one here can help me out. The build is a 249" girdled 109 with 6.35" rods and 9:1 compression It has GN1 heads, 212/218 hydraulic roller, scorpion rockers and a twin scroll Borg Warner EFR 8374 running on e85 with 160 lb injectors. Every thing is managed by the SD2/Powerlogger. No matter where I set the boost (10 psi or 25 psi) or timing (17-21 degrees) I still get KR. The weirder part about it is that it doesn't always do it. I also noticed that rolling into the throttle seems to reduce the knock rather than just stabbing the throttle. I've done all the basic checks to make sure the exhaust isn't hitting etc, and motor mounts are new H&R's. I've replaced and properly torqued the knock sensor and even tried several different ESC modules. The ethanol content is 75%. I'm attaching a recent log in the hopes that someone has an idea of what this could possibly be. Thanks in advance for y'alls help.

Paul

 

[Paul69camaro]

Couple things to add. I looked over the tables again this morning and noticed the file in the log posted above got corrupted and switched some cells in the tables around. I fixed the tune this morning and went out for another test with the results being the same. I did notice that I had the knock retard ignore set to 1.5 seconds which explains the delay in the knock showing up in the log. With it set to 0 it starts showing KR even before the boost comes in as the converter is stalling. I can get it to show KR by just reving it in neutral/park. I do have a slight exhaust leak at the joint in the crossover pipe. Is it possible for this to cause issues related to KR?

 

[~JM~]

Tranny X-member bushing?

Several months back, another member found that as a source of KR.

 

[BEATAV8]

How is the knock sensor installed and torqued? Is there any tape or goo on the knock sensor threads?

The knock sensor is an electrical gizmo. It needs a good ground to work correctly, as does the ESC module. If the sensor is taped up it may have intermittent grounding which will make the ESC go nuts.

 

[Paul69camaro]

I'll double check the cross member bushings tomorrow. Thanks for the tip.

As far as the knock sensor, it is brand new with only the red thread locker stuff that comes on it from factory, and it is not over tightened. The old sensor was replaced with this one but they act identical.

 

[BEATAV8]

under-tightened can be more troublesome for grounding problems (under-tightening is very common too). I believe the spec is 14 ft*lb. Set it there and continue the search for the culprit. If the sensor is under-tight then it may be a contributor or partial contributor and make the search that much more troublesome.

Check ESC electrical pins at both the ESC and the ECM. Look for any corrosion. If I remember correctly the ESC signal wire is yellow/black, pin B7. When voltage falls low on B7, thats when the ECM registers knock counts, so any corrosion causing extra resistance on this line will cause major problems.
Verify 12V power at the ESC, wiggle wires, etc. Check ESC ground wire condition and maybe measure resistance from ESC ground to battery ground. If I remember correctly the ESC ground is one of the many grounds at the rear of the passenger side cylinder head. Also check condition of the green signal wire & terminals from knock sensor to ESC.

Once you happy with electrical stuff, carry on looking for mechanical stuff.

 

[Paul69camaro]

Great info! I'll go through that this weekend and report back. Thanks for taking the time to type all that out.

 

[Mr.Spool]

I've been chasing this KR for a few months now and I'm all out of ideas. I'm pretty confident its false but I'm hoping some one here can help me out. The build is a 249" girdled 109 with 6.35" rods and 9:1 compression It has GN1 heads, 212/218 hydraulic roller, scorpion rockers and a twin scroll Borg Warner EFR 8374 running on e85 with 160 lb injectors. Every thing is managed by the SD2/Powerlogger. No matter where I set the boost (10 psi or 25 psi) or timing (17-21 degrees) I still get KR. The weirder part about it is that it doesn't always do it. I also noticed that rolling into the throttle seems to reduce the knock rather than just stabbing the throttle. I've done all the basic checks to make sure the exhaust isn't hitting etc, and motor mounts are new H&R's. I've replaced and properly torqued the knock sensor and even tried several different ESC modules. The ethanol content is 75%. I'm attaching a recent log in the hopes that someone has an idea of what this could possibly be. Thanks in advance for y'alls help.

Paul

What is the Afr and rpm when the knock happens?

 

[Paul69camaro]

The knock can happen as soon as the rpm ramps up. It shows knock at 10.8 a/f on e85

 

[RmvBfrFlght]

Pull the spark plugs and look for peppering on the center porcelain. If none is present then the knock is false. If peppering is present then at some point there is real knock.

RemoveBeforeFlight

 

[Evaddave 87gn]

Here is a long shot to check.

I came across a post the other day while researching cam sensor gear wear. The member stated similar issue with knock and it turned out to be the cap was
installed 180° out. Lots of discussion went back and forth about the fuel system running in batch mode because if this....sorry I do not remember which post it was or who the member was.

Dave

 

[Mr.Spool]

The knock can happen as soon as the rpm ramps up. It shows knock at 10.8 a/f on e85

try new plugs and regap

 

[Paul69camaro]

I've tried 2 different sets of plugs, Gap is down to .022 now on Bison's recommendation. It fixed the spark blow out issue but the knock is still present. There is no peppering on the plugs. I have not had time to mess with the car in quite a while. I plan to install the SSI map, kenne bell BAP and coolant pressure transducer in the next month or so. I'm pretty sure cam sensor is not 180 out, I pulled the #1 spark plug and made sure it had pressure as it rotated near TDC, then set it to 25 after TDC and set the sensor using Casper's tool...

 

[Mr.Spool]

I've tried 2 different sets of plugs, Gap is down to .022 now on Bison's recommendation. It fixed the spark blow out issue but the knock is still present. There is no peppering on the plugs. I have not had time to mess with the car in quite a while. I plan to install the SSI map, kenne bell BAP and coolant pressure transducer in the next month or so. I'm pretty sure cam sensor is not 180 out, I pulled the #1 spark plug and made sure it had pressure as it rotated near TDC, then set it to 25 after TDC and set the sensor using Casper's tool...

If you are getting knock in neutral under no load and no boost take a closer look look at the motor itself.comp test the motor or leak it down.when you pulled the plugs how did they look uniform?how was the color and burn marks?does it feel like it misses when you drive it.if the motor checks out and the plugs look good and the car doesn't miss at all you could also try to richen it up.

 

[SCOOBY DOO]

Looking at the file it doesn't appear to be real...and it's hearing something. Last one we chased ended up being a broken cam button spring.

 

[Paul69camaro]

I'm thinking of just ignoring the knock sensor and adding the coolant pressure transducer. I plan to find the tune limit and then back off substantially. This knock sensor issue has exhausted my patience.

P.s. As I say that... one more thought, the timing chain broke in the last motor and broke the snout in the old cam. I'm using the same cam sensor... I've inspected it and it looks fine, very little play, maybe something got damaged...

 

[dynoman]

Did you check torque converter bolts ?

 

[Mark Harrington]

I'm thinking of just ignoring the knock sensor and adding the coolant pressure transducer. I plan to find the tune limit and then back off substantially. This knock sensor issue has exhausted my patience.

P.s. As I say that... one more thought, the timing chain broke in the last motor and broke the snout in the old cam. I'm using the same cam sensor... I've inspected it and it looks fine, very little play, maybe something got damaged...

I have read 100 knock post, no one tells how they resolved it.... what did you find?

 

[TireFryer]

My knock issue was my transmission. Rebuilt it and got the slipping fixed and boom. No more KR. Also new tranny mount bushing. Still get about .2-.5 on the shifts

 

[Mark Harrington]

Thanks, how were you able to diagnose the transmission?