False knock driving me crazy, help please

[Flyin Brian]

Ok, I know this subject has been beat to death and I have searched the forum and found lots of information but I have intermittent false knock that is driving me crazy and I don't know what path to take. I can floor it off the line and get tons of knock retard (see below) sometimes and none other times. I am sure it is false knock as I can hammer it in third all day long and get no knock retard (see next image later in the same run).

I like the idea of having a knock detector for safety but tons of other people run without one and just watch the wideband or egt's and read the plugs and are fine. My plugs don't show any sign of detonation. The car runs terrible when it yanks out 15 degrees of timing for no reason. I am only running 18 psi boost and 23 degrees of timing on E85 so there should be no knock as rich as I am running it. I have gone through the checklist and checked or replaced almost everfything. I have a new knock sensor and it is not overtightened. Almost everything under the hood is new. The only thing that I have not replaced is the ESC module and the engine wiring harness. Any suggestions? Should I just run without the knock sensor? Any input would be greatly appreciated.

 

[87BLKGN]

Just taking a guess, could it possibly be a faulty knock sensor?

 

[Flyin Brian]

I could try another knock sensor I guess. They are not that expensive but this is the second one I have tried. Bought it new a few months ago and had no effect.

 

[Mr.Spool]

check the downpipe for clearence or anything else that could move around.

 

[dpasadena]

I have the same pistons and most likely the same crank and battled false knock for a long time. I carefully ran the car without the knock sensor and it performed well. Recently, while beating on the car, a rod bearing failed. During inspection, found out the pistons were barely hitting the heads causing the knock. Mine would only knock above 17psi or so.

 

[dpasadena]

I could try another knock sensor I guess. They are not that expensive but this is the second one I have tried. Bought it new a few months ago and had no effect.

Don't waste your money on more knock sensors. Been there! Have a few new ones on my shelf

 

[Flyin Brian]

check the downpipe for clearence or anything else that could move around.

Thanks. The downpipe is close to the frame and has come in contact with it. I can tell as I have it insulated and there is damage to the insulation wrap where it hits the frame. I have tried tightening the torque strap to it won't hit and have tried loosening it as well. Nothing seems to help and the irritating thing is that the false knock happens some days and does not happen other days under the same conditions. It does regularly happen on the 1-2 and 2-3 shifts and downshifts too. I could clearance the pipe more I guess.

 

[Flyin Brian]

I have the same pistons and most likely the same crank and battled false knock for a long time. I carefully ran the car without the knock sensor and it performed well. Recently, while beating on the car, a rod bearing failed. During inspection, found out the pistons were barely hitting the heads causing the knock. Mine would only knock above 17psi or so.

Sorry to hear about your motor Dave. That bites. I really hope my pistons are not kissing the heads. My engine builder hopefully checked that. He used a thicker head gasket to get the compression to 9:1. He is one of the premier Buick v6 builders in this area so I hope it is right. My knock is so intermittent I don't think it is a mechanical problem. At lease I hope it is not. How did you disable your knock detector? My car is running really good now on the days that the false knock is not happening by the way. I am almost there!

 

[Frank87gn]

check your boost guage, you might have more than 18 psi boost. You may have a small leak in boost line. So you may be actually running 25 psi and showing 18 psi. Just a thought.

 

[TurboBuRick]

Post the log file.

RL

 

[Flyin Brian]

Here is the log file. Other days I can take a drive and hammer it and get minimal or no knock retard.

 

[Fast4Ward]

pull your timing back and bring down the boost...you can rule out the pipe this way and confirm that something other than pipe is causing it.
i can get knock as high as 19 on a violent down shift running alky, 25/24 timing, boost kissing 29....most of the time no knock even from a down shift.
that pipe is a pita. release strap and put a flat wrench between rail and pipe before tightening it down.

 

[Sixxshot87]

SOUNDS TO ME LIKE SOMEONE IS SPINNING SOME TIRE! tire spin has always gotten me the knock gremlin from no where, slicks fixed it, it happened when i couldn't afford slicks but was so used to driving on them it never occurred wheel spin did it. my 2c

 

[TurboBuRick]

When the throttle is lifted knock retard stays on 10. Got to be false.

The way the KR trace flat lines, I'm thinking electronic gremlin.

Whats the new feed wire to ecm?

RL

 

[Jerryl]

When the throttle is lifted knock retard stays on 10. Got to be false.

The way KR trace flat lines, I'm thinking electronic gremlin.

Whats the new feed wire to ecm?

RL

x2.
It's not tire spin either . . .

OP,
Have you gone through the complete checklist?

suicide six said: ↑

Start going thru this list.............Turbo Regal Knock Problem Check List​

1. Start-up knock? Normal and usually caused by the starter engaging the flex plate. Usually sets off 1-3 lights.​

2. Possible bad ECM or ESC module. Test with good working units.​

3. Exhaust rattle – check the down pipe, tail pipes, and have engine tie down strap​

4. Boost creep especially top of 1st gear on 1-2 shift.​

5. Lean air/fuel mixture.​

6. To low octane gas – bad pump gas – try some race gas​

7. Too much timing in chip for fuel used. Try different chip.​

8. Try cooler spark plugs – use only AC Delco (R43-TS or R42-TS)​

9. Gap plugs to .035​

10. Check torque converter bolts to make sure they are tight​

11. Loose harmonic balancer. Make sure torqued to 200 ft/lb Is keyway secure?​

12. Check internal engine noises like timing chains (roller), lifters/rockers, etc.​

13. Damaged knock sensor​

14. Check fuel pump pressure and volume​

15. Proper torque on knock sensor – 14 ft/lb​

16. Check Alternator voltage: 13.8 - 14.5v​

17. Check computer power wire - they can break internally.​

18. Troubleshoot the computer connector power wires and ground wires.​

19. Swap coil pack, wires, plugs w/known good units.​

20. Swap MAF with known good unit.​

21. Check battery ground connection @ block (clean/inspect).​

22. Check/change battery cables (both).​

23. Are there MAF leaks in the inlet tube?​

24. Are there vacuum leaks. Use carb cleaner or WD-40 & spray everything. Does the rpm change?​

25. Disconnect the main injector harness - inspect, WD-40. Check for moisture in main connector.​

26. Disconnect the coil-pack connector - inspect pins & spray w/WD-40.​

27. Is the cat still installed? Is it good?​

28. Have you performed a leak down check?​

29. Do the rockers open/close? Do we have a wiped cam lobe?​

30. Is the boost/vacuum steady @ idle?​

31. Is the engine over revving? Should be 4,800-5,200 rpm​

32. Carbon in cylinders? Clean with GM engine top cleaner​

33. Inter-cooler dirty? Clean inside inter-cooler and fins​

34. Oil in intake tract?​

35. Check for exhaust leaks, cracked header​

36. Battery good?​

37. EGR valve in working order?​

38. Check that no cables, wires, etc are touching the knock sensor​

39. Blown head gasket? Compression test. Should be around 150.​

40. Injectors flowing/working correctly?​

41. Check vacuum line to fuel pressure regulator for cracks​

__________________​

 

[BEATAV8]

I agree, I think Rick is correct. That flatline KR is very strange, don't think I've ever seen that before. And like Rick mentioned it's just hanging around even after you let off. Strong possibility of an electrical gremlin. Ground issue, corroded pin/terminal at ECM connector, etc etc... Might even be an issue with the chip.

 

[Flyin Brian]

pull your timing back and bring down the boost...you can rule out the pipe this way and confirm that something other than pipe is causing it.
i can get knock as high as 19 on a violent down shift running alky, 25/24 timing, boost kissing 29....most of the time no knock even from a down shift.
that pipe is a pita. release strap and put a flat wrench between rail and pipe before tightening it down.

Pipe is a pita for sure. Fitup was difficult. I can pull timing and run rich and still get the crazy knock. It has to be false. I do still have the stock downpipe I can put back on to test with.

 

[Flyin Brian]

SOUNDS TO ME LIKE SOMEONE IS SPINNING SOME TIRE! tire spin has always gotten me the knock gremlin from no where, slicks fixed it, it happened when i couldn't afford slicks but was so used to driving on them it never occurred wheel spin did it. my 2c

I am lighting the drag radials at will below 30 mph when I hit it but the knock does not always happen when the wheels are spinning. Sometimes I can hammer it from a standstill and burn them all the way to third with no knock and other times it pulls timing like crazy.

 

[Flyin Brian]

When the throttle is lifted knock retard stays on 10. Got to be false.

The way the KR trace flat lines, I'm thinking electronic gremlin.

Whats the new feed wire to ecm?

RL

I am starting to think that too. I replaced a section of the ECM feed wire from the battery to close to where it enters the rest of the harness by the ac box as the wire that was there was looking weak and some of my log data was looking glitchy. No change. I was getting a prom socket error before so I replaced the ECM and that fixed that. I have fixed all the grounds and every other bad looking wire that I can find but I still get the intermittent crazy knock retard. I am thinking of replacing the ESC module and if that does not work I am thinking of pulling the entire wiring harness and checking it out. Could possibly be damaged down where it feeds through the passenger side firewall where I can't see it?? This car did sit in a field for years before I bought it.

 

[Flyin Brian]

x2.
It's not tire spin either . . .

OP,
Have you gone through the complete checklist?

suicide six said: ↑

Start going thru this list.............Turbo Regal Knock Problem Check List​

1. Start-up knock? Normal and usually caused by the starter engaging the flex plate. Usually sets off 1-3 lights.​

2. Possible bad ECM or ESC module. Test with good working units.​

3. Exhaust rattle – check the down pipe, tail pipes, and have engine tie down strap​

4. Boost creep especially top of 1st gear on 1-2 shift.​

5. Lean air/fuel mixture.​

6. To low octane gas – bad pump gas – try some race gas​

7. Too much timing in chip for fuel used. Try different chip.​

8. Try cooler spark plugs – use only AC Delco (R43-TS or R42-TS)​

9. Gap plugs to .035​

10. Check torque converter bolts to make sure they are tight​

11. Loose harmonic balancer. Make sure torqued to 200 ft/lb Is keyway secure?​

12. Check internal engine noises like timing chains (roller), lifters/rockers, etc.​

13. Damaged knock sensor​

14. Check fuel pump pressure and volume​

15. Proper torque on knock sensor – 14 ft/lb​

16. Check Alternator voltage: 13.8 - 14.5v​

17. Check computer power wire - they can break internally.​

18. Troubleshoot the computer connector power wires and ground wires.​

19. Swap coil pack, wires, plugs w/known good units.​

20. Swap MAF with known good unit.​

21. Check battery ground connection @ block (clean/inspect).​

22. Check/change battery cables (both).​

23. Are there MAF leaks in the inlet tube?​

24. Are there vacuum leaks. Use carb cleaner or WD-40 & spray everything. Does the rpm change?​

25. Disconnect the main injector harness - inspect, WD-40. Check for moisture in main connector.​

26. Disconnect the coil-pack connector - inspect pins & spray w/WD-40.​

27. Is the cat still installed? Is it good?​

28. Have you performed a leak down check?​

29. Do the rockers open/close? Do we have a wiped cam lobe?​

30. Is the boost/vacuum steady @ idle?​

31. Is the engine over revving? Should be 4,800-5,200 rpm​

32. Carbon in cylinders? Clean with GM engine top cleaner​

33. Inter-cooler dirty? Clean inside inter-cooler and fins​

34. Oil in intake tract?​

35. Check for exhaust leaks, cracked header​

36. Battery good?​

37. EGR valve in working order?​

38. Check that no cables, wires, etc are touching the knock sensor​

39. Blown head gasket? Compression test. Should be around 150.​

40. Injectors flowing/working correctly?​

41. Check vacuum line to fuel pressure regulator for cracks​

__________________​

Thanks. I have gone through most of this list. Almost everything in this car is new and has less than 1500 miles on it except for the ESC module and the wiring harness. Electrical problems suck