Getting knock on hard acceleration. I'm using 91 octane (no ethanol). I have 23,000 miles on original plugs and am wondering if I should try to change them or if I should have it tuned first. I'm thinking of just having the tune done. There aren't any performance shops around, so I'm talking about taking it to the dealership.

There are no current codes.

 

Have you tried using 93 octane?

 

That's not available here, but I've tried it on road trips and the knocking stops. By the way, my engine is all stock except for a K&N air filter. I haven't had to clean or re-oil it yet.

 

Tunes dont go bad, so that wouldnt be causing the knock. How new is this development?

 

I've had the car for about a year and it has been there that long. Could a dirty MAF cause knock?

 

I think the OP is talking about getting it tuned to run on 91 octane. Not re-tuned.

 

The PCM contains 2 spark tables. High and Low octane. When the pcm detects knock, it begins to transition to and use the low octane table. The low octane table has significantly reduced timing.
So, sounds like either the knock sensors aren't working, have been retuned (sensitivity changed) or someone made the low octane table the same as the high octane table.

Again, a case where datalogging with HPT or EFI live while driving would reveal what is going on. Certainly could read the current tune and see if it has been messed with.

Ron

 

You know... I have the Torque Ap for my smartphone and I think it gives a complete readout on it's knock sensor program. Just snowed here so it will be a few days, but I'll get out and test it and report back on what it says in a couple of days.

Thanks!

 

Cool, I mean cold! Good luck.

Ron

 

Ok, roads were bare and dry today so I got out and did the knock tests using the Torque ap on my Android phone. I did the test twice, starting at 35mph and hitting full throttle. The test only takes about 2 seconds and the speeds listed below are in error, as I never exceeded about 60mph. How does the timing look?

Test One:

"1 knock event from 7 samples.
knock event 1:
RPM 3,766.75, speed 87.3
Timing 29, Correction -1"

Test Two:

"2 knock events from 11 samples.
knock event 1:
RPM 3,541, speed 81.9
Timing 30.5, Correction -0.5

knock event 2:
RPM 3626, speed 86.4
Timing 30, Correction -0.5"

Personally, when I actually hear the knock, it's when I'm accelerating on a freeway onramp without using a lot of throttle and the transmission just kicking down into 3rd. Situations like that.

I also have the following test results that are taken with the same Torque ap and the engine at idle. I don't have a clue what these mean:

Mode $06 report generated by Torque for Android
======================================== ========

Vehicle VIN: 1G1YY22G845102035
Vehicle Manufacturer: Chevrolet
Vehicle Calibration ID: 12585950
12586112
1258

Unit and scaling information are not supplied with the data from the ECU for this type of vehicle. Consulting the manufacturers service book for this information is recommended.

Test report:
------------------
TID:$02 CID:$04
- Lean to Rich sensor threshold voltage(constant)
Test incomplete or dependant test failed
--
TID:$02 CID:$06
- Lean to Rich sensor threshold voltage(constant)
Min: 32,868
Test result value: 32,868
PASS
----
TID:$02 CID:$11
- Lean to Rich sensor threshold voltage(constant)
Min: 375
Test result value: 376
PASS
----
TID:$02 CID:$30
- Lean to Rich sensor threshold voltage(constant)
Test incomplete or dependant test failed
--
TID:$02 CID:$40
- Lean to Rich sensor threshold voltage(constant)
Test incomplete or dependant test failed
--
TID:$02 CID:$50
- Lean to Rich sensor threshold voltage(constant)
Min: 32,898
Test result value: 32,898
PASS
----
TID:$02 CID:$60
- Lean to Rich sensor threshold voltage(constant)
Max: 33,018
Test result value: 32,778
PASS
----
TID:$02 CID:$66
- Lean to Rich sensor threshold voltage(constant)
Max: 32,838
Test result value: 32,774
PASS
----
TID:$02 CID:$71
- Lean to Rich sensor threshold voltage(constant)
Max: 32,888
Test result value: 32,763
PASS
----
TID:$05 CID:$01
- Rich to Lean sensor switch time(calculated)
Max: 65,535
Test result value: 14,944
PASS
----
TID:$05 CID:$02
- Rich to Lean sensor switch time(calculated)
Max: 65,535
Test result value: 14,944
PASS
----
TID:$05 CID:$03
- Rich to Lean sensor switch time(calculated)
Max: 65,535
Test result value: 8,000
PASS
----
TID:$05 CID:$04
- Rich to Lean sensor switch time(calculated)
Max: 65,535
Test result value: 19,999
PASS
----
TID:$05 CID:$05
- Rich to Lean sensor switch time(calculated)
Max: 16,320
Test result value: 2,368
PASS
----
TID:$05 CID:$06
- Rich to Lean sensor switch time(calculated)
Max: 16,320
Test result value: 1,856
PASS
----
TID:$05 CID:$07
- Rich to Lean sensor switch time(calculated)
Min: 15
Test result value: 108
PASS
----
TID:$05 CID:$08
- Rich to Lean sensor switch time(calculated)
Min: 15
Test result value: 102
PASS
----
TID:$05 CID:$0a
- Rich to Lean sensor switch time(calculated)
Max: 1,450
Test result value: 104
PASS
----
TID:$05 CID:$0b
- Rich to Lean sensor switch time(calculated)
Min: 22,719
Test result value: 22,914
PASS
----
TID:$05 CID:$0d
- Rich to Lean sensor switch time(calculated)
Max: 32,888 Min: 32,568
Test result value: 32,776
PASS
----
TID:$05 CID:$41
- Rich to Lean sensor switch time(calculated)
Max: 65,535
Test result value: 14,944
PASS
----
TID:$05 CID:$42
- Rich to Lean sensor switch time(calculated)
Max: 65,535
Test result value: 14,944
PASS
----
TID:$05 CID:$43
- Rich to Lean sensor switch time(calculated)
Max: 65,535
Test result value: 8,000
PASS
----
TID:$05 CID:$44
- Rich to Lean sensor switch time(calculated)
Max: 65,535
Test result value: 19,999
PASS
----
TID:$05 CID:$45
- Rich to Lean sensor switch time(calculated)
Max: 16,320
Test result value: 2,688
PASS
----
TID:$05 CID:$46
- Rich to Lean sensor switch time(calculated)
Max: 16,320
Test result value: 2,368
PASS
----
TID:$05 CID:$47
- Rich to Lean sensor switch time(calculated)
Min: 15
Test result value: 105
PASS
----
TID:$05 CID:$48
- Rich to Lean sensor switch time(calculated)
Min: 15
Test result value: 106
PASS
----
TID:$05 CID:$4a
- Rich to Lean sensor switch time(calculated)
Max: 1,450
Test result value: 91
PASS
----
TID:$05 CID:$4b
- Rich to Lean sensor switch time(calculated)
Min: 22,719
Test result value: 22,775
PASS
----
TID:$05 CID:$4d
- Rich to Lean sensor switch time(calculated)
Max: 32,888 Min: 32,568
Test result value: 32,773
PASS
----
TID:$0a CID:$0a
- Sensor period(calculated)
Max: 168
Test result value: 22
PASS
----
TID:$0c CID:$60
- Misfire counts for last/current driving cycles(calculated)
Max: 33,069
Test result value: 17,780
PASS
----
TID:$0c CID:$70
- Misfire counts for last/current driving cycles(calculated)
Max: 33,069
Test result value: 17,778
PASS
----
TID:$02 CID:$04
- Lean to Rich sensor threshold voltage(constant)
Test incomplete or dependant test failed
--
TID:$02 CID:$06
- Lean to Rich sensor threshold voltage(constant)
Min: 32,868
Test result value: 32,868
PASS
----
TID:$02 CID:$11
- Lean to Rich sensor threshold voltage(constant)
Min: 375
Test result value: 376
PASS
----
TID:$02 CID:$30
- Lean to Rich sensor threshold voltage(constant)
Test incomplete or dependant test failed
--
TID:$02 CID:$40
- Lean to Rich sensor threshold voltage(constant)
Test incomplete or dependant test failed
--
TID:$02 CID:$50
- Lean to Rich sensor threshold voltage(constant)
Min: 32,898
Test result value: 32,898
PASS
----
TID:$02 CID:$60
- Lean to Rich sensor threshold voltage(constant)
Max: 33,018
Test result value: 32,778
PASS
----
TID:$02 CID:$66
- Lean to Rich sensor threshold voltage(constant)
Max: 32,838
Test result value: 32,774
PASS
----
TID:$02 CID:$71
- Lean to Rich sensor threshold voltage(constant)
Max: 32,888
Test result value: 32,763
PASS
----
TID:$05 CID:$01
- Rich to Lean sensor switch time(calculated)
Max: 65,535
Test result value: 14,944
PASS
----
TID:$05 CID:$02
- Rich to Lean sensor switch time(calculated)
Max: 65,535
Test result value: 14,944
PASS
----
TID:$05 CID:$03
- Rich to Lean sensor switch time(calculated)
Max: 65,535
Test result value: 8,000
PASS
----
TID:$05 CID:$04
- Rich to Lean sensor switch time(calculated)
Max: 65,535
Test result value: 19,999
PASS
----
TID:$05 CID:$05
- Rich to Lean sensor switch time(calculated)
Max: 16,320
Test result value: 2,368
PASS
----
TID:$05 CID:$06
- Rich to Lean sensor switch time(calculated)
Max: 16,320
Test result value: 1,856
PASS
----
TID:$05 CID:$07
- Rich to Lean sensor switch time(calculated)
Min: 15
Test result value: 108
PASS
----
TID:$05 CID:$08
- Rich to Lean sensor switch time(calculated)
Min: 15
Test result value: 102
PASS
----
TID:$05 CID:$0a
- Rich to Lean sensor switch time(calculated)
Max: 1,450
Test result value: 104
PASS
----
TID:$05 CID:$0b
- Rich to Lean sensor switch time(calculated)
Min: 22,719
Test result value: 22,914
PASS
----
TID:$05 CID:$0d
- Rich to Lean sensor switch time(calculated)
Max: 32,888 Min: 32,568
Test result value: 32,776
PASS
----
TID:$05 CID:$41
- Rich to Lean sensor switch time(calculated)
Max: 65,535
Test result value: 14,944
PASS
----
TID:$05 CID:$42
- Rich to Lean sensor switch time(calculated)
Max: 65,535
Test result value: 14,944
PASS
----
TID:$05 CID:$43
- Rich to Lean sensor switch time(calculated)
Max: 65,535
Test result value: 8,000
PASS
----
TID:$05 CID:$44
- Rich to Lean sensor switch time(calculated)
Max: 65,535
Test result value: 19,999
PASS
----
TID:$05 CID:$45
- Rich to Lean sensor switch time(calculated)
Max: 16,320
Test result value: 2,688
PASS
----
TID:$05 CID:$46
- Rich to Lean sensor switch time(calculated)
Max: 16,320
Test result value: 2,368
PASS
----
TID:$05 CID:$47
- Rich to Lean sensor switch time(calculated)
Min: 15
Test result value: 105
PASS
----
TID:$05 CID:$48
- Rich to Lean sensor switch time(calculated)
Min: 15
Test result value: 106
PASS
----
TID:$05 CID:$4a
- Rich to Lean sensor switch time(calculated)
Max: 1,450
Test result value: 91
PASS
----
TID:$05 CID:$4b
- Rich to Lean sensor switch time(calculated)
Min: 22,719
Test result value: 22,775
PASS
----
TID:$05 CID:$4d
- Rich to Lean sensor switch time(calculated)
Max: 32,888 Min: 32,568
Test result value: 32,773
PASS
----
TID:$0a CID:$0a
- Sensor period(calculated)
Max: 168
Test result value: 22
PASS
----
TID:$0c CID:$60
- Misfire counts for last/current driving cycles(calculated)
Max: 33,069
Test result value: 17,780
PASS
----
TID:$0c CID:$70
- Misfire counts for last/current driving cycles(calculated)
Max: 33,069
Test result value: 17,778
PASS
----
TID:$02 CID:$04
- Lean to Rich sensor threshold voltage(constant)
Test incomplete or dependant test failed
--
TID:$02 CID:$06
- Lean to Rich sensor threshold voltage(constant)
Min: 32,868
Test result value: 32,868
PASS
----
TID:$02 CID:$11
- Lean to Rich sensor threshold voltage(constant)
Min: 375
Test result value: 376
PASS
----
TID:$02 CID:$30
- Lean to Rich sensor threshold voltage(constant)
Test incomplete or dependant test failed
--
TID:$02 CID:$40
- Lean to Rich sensor threshold voltage(constant)
Test incomplete or dependant test failed
--
TID:$02 CID:$50
- Lean to Rich sensor threshold voltage(constant)
Min: 32,898
Test result value: 32,898
PASS
----
TID:$02 CID:$60
- Lean to Rich sensor threshold voltage(constant)
Max: 33,018
Test result value: 32,778
PASS
----
TID:$02 CID:$66
- Lean to Rich sensor threshold voltage(constant)
Max: 32,838
Test result value: 32,774
PASS
----
TID:$02 CID:$71
- Lean to Rich sensor threshold voltage(constant)
Max: 32,888
Test result value: 32,763
PASS
----
TID:$05 CID:$01
- Rich to Lean sensor switch time(calculated)
Max: 65,535
Test result value: 14,944
PASS
----
TID:$05 CID:$02
- Rich to Lean sensor switch time(calculated)
Max: 65,535
Test result value: 14,944
PASS
----
TID:$05 CID:$03
- Rich to Lean sensor switch time(calculated)
Max: 65,535
Test result value: 8,000
PASS
----
TID:$05 CID:$04
- Rich to Lean sensor switch time(calculated)
Max: 65,535
Test result value: 19,999
PASS
----
TID:$05 CID:$05
- Rich to Lean sensor switch time(calculated)
Max: 16,320
Test result value: 2,368
PASS
----
TID:$05 CID:$06
- Rich to Lean sensor switch time(calculated)
Max: 16,320
Test result value: 1,856
PASS
----
TID:$05 CID:$07
- Rich to Lean sensor switch time(calculated)
Min: 15
Test result value: 108
PASS
----
TID:$05 CID:$08
- Rich to Lean sensor switch time(calculated)
Min: 15
Test result value: 102
PASS
----
TID:$05 CID:$0a
- Rich to Lean sensor switch time(calculated)
Max: 1,450
Test result value: 104
PASS
----
TID:$05 CID:$0b
- Rich to Lean sensor switch time(calculated)
Min: 22,719
Test result value: 22,914
PASS
----
TID:$05 CID:$0d
- Rich to Lean sensor switch time(calculated)
Max: 32,888 Min: 32,568
Test result value: 32,776
PASS
----
TID:$05 CID:$41
- Rich to Lean sensor switch time(calculated)
Max: 65,535
Test result value: 14,944
PASS
----
TID:$05 CID:$42
- Rich to Lean sensor switch time(calculated)
Max: 65,535
Test result value: 14,944
PASS
----
TID:$05 CID:$43
- Rich to Lean sensor switch time(calculated)
Max: 65,535
Test result value: 8,000
PASS
----
TID:$05 CID:$44
- Rich to Lean sensor switch time(calculated)
Max: 65,535
Test result value: 19,999
PASS
----
TID:$05 CID:$45
- Rich to Lean sensor switch time(calculated)
Max: 16,320
Test result value: 2,688
PASS
----
TID:$05 CID:$46
- Rich to Lean sensor switch time(calculated)
Max: 16,320
Test result value: 2,368
PASS
----
TID:$05 CID:$47
- Rich to Lean sensor switch time(calculated)
Min: 15
Test result value: 105
PASS
----
TID:$05 CID:$48
- Rich to Lean sensor switch time(calculated)
Min: 15
Test result value: 106
PASS
----
TID:$05 CID:$4a
- Rich to Lean sensor switch time(calculated)
Max: 1,450
Test result value: 91
PASS
----
TID:$05 CID:$4b
- Rich to Lean sensor switch time(calculated)
Min: 22,719
Test result value: 22,775
PASS
----
TID:$05 CID:$4d
- Rich to Lean sensor switch time(calculated)
Max: 32,888 Min: 32,568
Test result value: 32,773
PASS
----

End of report.

 

bump.

 

Still looking for help.

 

SEAFOAM is the answer.. Been there and done that with both my C5s