Getting KR on very slight deceleration as well as with Boost.

Tyler Stipe

New Member
Apr 21, 2017
I've searched all over for ideas and answers on fixing my KR. Cruising it seems just fine, but if I just barely let off the gas, it seems to get some KR, but if I fully let off the gas it jumps to 0 KR.

Also, during boost, I'm getting some serious amounts of KR. I'm running 93 octane with royal purple octane booster, was trying to make sure it wasn't because of low octane, still does it.

Video examples:

This has both deceleration and boost KR

This has just the deceleration KR

Please excuse the crappy video quality, as I was trying to drive and record at the same time.

Here is a list of the mods the previous owner did:

  1. Stock 109 block with forged Speed Pro pistons,
  2. shot-peened rods,
  3. stock crankshaft,
  4. steel center main caps.
  5. Fully balanced and blueprinted by Wildcat performance in Adel Georgia. Factory cylinder heads with 2.02/1.55 valves and light port and bowl work. Autolite 23 spark plugs gapped at .035. Precision Turbo 6766 journal bearing turbocharger.
  6. GN1 headers and 3.5 inch down pipe. Tubular upper control arms to clear the down pipe.
  7. LS1 starter.
  8. 3 inch front mount intercooler
  9. LS1 MAF and translator.
  10. Turbotweak chip with Power Logger. Custom 235mm billet 3500 stall single disc lock-up torque converter built by Greg Chomos.
  11. Turbo Buick to 4L80E adapter. Full billet 4l80E trans built by Kris at CK performance transmissions.
  12. TCI transmission controller.
  13. Custom 3 inch steel balanced driveshaft with 1350 u-joints.
  14. Forged pinion yoke.
  15. Strange 31 spline axles with full spool and c-clip eliminators.
  16. 5/8" wheel studs. ARP hardware throughout.
  17. TA cover with girdle.
  18. Adjustable upper control arms with solid lowers. ATR rear sway bar.
  19. Racetronix full kit with twin Aeromotive 340 pumps and new high flow sending unit.
  20. Setup for the second fuel pump to come on at 15 lbs of boost.
  21. 42lb injectors.
  22. Bailey engineering 2-step.
  23. Devils Own Alcohol injection. AEM Truboost boost controller.
  24. Autometer wideband O2 gauge.
  25. Caspers knock gauge.
  26. Custom 1 piece front chin spoiler. Competition Engineering 3 way adjustable front shocks.
  27. QA1 15 way adjustable rear shocks.
  28. Weld Alumastars on the front with Holeshot rears.

I've had the car about a month now and I've replaced or installed:

  1. TR6 + Coil/Wires from Bob
  2. Scanmaster G
  3. Brand New MAF Sensor
  4. 4" Exhaust
  5. NKG Plugs, now gapped at .25
  6. New Rear Coil Springs

Fixed/Repaired shotty/half assed work the previous owner did, finding new stuff every day to fix/repair.

I am not hearing any kind of audible knock. I did just last week put on the 4" single exhaust with Magnaflow straight through muffler. Since then, at about 0 boost, roughly, the car starts vibrating, higher into boost it goes away.

Based on the video, am I running too rich and possibly getting rich knock? Is it most likely false knock from something? It's driving me nuts, I've been looking all over for something possibly banging on the engine somewhere. Downpipe is not hitting anything, plenty of clearance.

I do have a brand new knock sensor in my possession, I have not installed it yet, as I've been reading it's a pain to torque correctly with the engine in the car.

Any suggestions or help would be much appreciated.

I will continue to browse google and these forums for possible solutions.

Last edited:
Might want to check the crankshaft play.
Torque on the sensor is?
Threads should be clean and sensor should be torqued to spec.
Very common to find the sensor installed loose and gummed up with wads of teflon tape. People thought this helped to desensitize the knock sensor when what it really does is mess up the electrical grounding. First and foremost the sensor and the knock filter are electrical components and integrity of the wiring and grounding is super important for proper function.

Also very common to find weak or broken grounding on the wires grounded to the rear of the passenger side cylinder head. The knock filter owns one of these ground wires.

Also common to find corroded ECM terminals on the main ECM connectors. Water leaks in from above (window weatherstrip leaks) and lands on the ECM connector, rotting out all the terminals and turning everything green. When the knock filter signal line rots out the resistance goes up, ecm sees low voltage on the line and interprets that as knock.
Check for exhaust system banging around on something.
BEATAV8.......So looked at my knock sensor and it has the Teflon tape on the threads. Dang IT!! I also have an intake that is ceramic coated. Any way to validate your theory of the knock sensor not grounding or poor connection with the ECM using a voltmeter ?
BEATAV8.......So looked at my knock sensor and it has the Teflon tape on the threads. Dang IT!! I also have an intake that is ceramic coated. Any way to validate your theory of the knock sensor not grounding or poor connection with the ECM using a voltmeter ?

Clean the threads in the block and the sensor. Reinstall at 14#/ft. Someone was playing grabass w/ a knock problem, and decided to do a fake "repair".
The coated intake has nothing to do w/ the knock issue.
Grnd issues can be found using volt drop testing.