What should the Desired AFR range normally be in mellow country road cruise?

I am new to data logging and am trying to chase down high knock counts on my 95 K2500 5.7 TBI all stock. It starts, idles and runs very well. I was surprised to see very high knock counts (over 10,000 after 20 min). Changed to cooler plug and tried 92 instead of 87 octane both with no change what so ever.

Happens on acceleration and mellow cruise 1600-2000 rpm. One question I have (other than what clues I can look for to pin point which of all the things that can cause knock this might be?) is the the Desired AFR never goes above 14.2 and seems to average 13.5 to 14 throughout the drive on mellow country roads. Is this normal or a clue to a problem? I guess I was expecting it to fluctuate more.

Any advice appreciated!

Have you checked the knock sensor ? I believe your AFR is in a ok range.

Gary

Are you hearing knock or just noticed it in the data logs?

Has the knock sensor been changed?

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Originally Posted by Stroked 388

Have you checked the knock sensor ? I believe your AFR is in a ok range.

Gary

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Thanks Gary - Not sure how to check the sensor to determine if it is giving false knock? The only thing ive seen is to tap to see if it registers. Any advise on how to check to see if it's over sensitive? Or should I just change it?

Quote - brian617

Are you hearing knock or just noticed it in the data logs?

Has the knock sensor been changed? - Quote

I don't hear anything. I don't believe the sensor has ever been changed. Perhaps I should just swap it out. Do they go bad in the direction of false knock?

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Originally Posted by brian617

Are you hearing knock or just noticed it in the data logs?

Has the knock sensor been changed?

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I don't hear anything at all. I don't believe the sensor has ever been changed. Do they go bad in the direction of false knock?

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Originally Posted by dharris894

I don't hear anything at all. I don't believe the sensor has ever been changed. Do they go bad in the direction of false knock?

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I have had them go bad to the point they retard the timing the maximum value the moment the PCM hits the knock retard activation thresholds in RPM/KPA.

Ya I don't know of a way other than what you read. If you have no motor noise like valve train lower end noise or resonating exhaust. It is possible for the knock sensor to be bad. Also there is a knock module in the ECM. As for your AFR being rich 14.7 should be the target value. But if it sences knock it can add fuel and remove timeing to try and fix it.

[QUOTE=dharris894;74037]

Thanks Gary - Not sure how to check the sensor to determine if it is giving false knock? The only thing ive seen is to tap to see if it registers. Any advise on how to check to see if it's over sensitive? Or should I just change it?

Quote - brian617

Are you hearing knock or just noticed it in the data logs?

Has the knock sensor been changed? - Quote

I don't hear anything. I don't believe the sensor has ever been changed. Perhaps I should just swap it out. Do they go bad in the direction of false knock?

[COLOR=#000000][/

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Originally Posted by Stroked 388

Ya I don't know of a way other than what you read. If you have no motor noise like valve train lower end noise or resonating exhaust. It is possible for the knock sensor to be bad. Also there is a knock module in the ECM. As for your AFR being rich 14.7 should be the target value. But if it sences knock it can add fuel and remove timeing to try and fix it.

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That depends on the fuel being used. If it is 10% ethanol stoichiometric is 14.1:1.

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Originally Posted by Fast355

That depends on the fuel being used. If it is 10% ethanol stoichiometric is 14.1:1.

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Yes very good point

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Originally Posted by Fast355

That depends on the fuel being used. If it is 10% ethanol stoichiometric is 14.1:1.

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So thats interesting. Does the ECM assume 10%? What happens if I use non-ethenol when it's expecting 10%? Could that contribute to knock counts?

Or does it not assume anything and can calculate somehow if the AFR should be 14.1 or 14.7?

On the 94-95 model trucks, the automatic and manual trans use different knock sensors because the the auto and manual trucks use different computers, PCM vs ECM. Be sure to get the correct sensor.

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Originally Posted by brian617

On the 94-95 model trucks, the automatic and manual trans use different knock sensors because the the auto and manual trucks use different computers, PCM vs ECM. Be sure to get the correct sensor.

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Nice catch -

Rockauto says that part 10456288 is correct for my truck without saying whether its manual or Auto.

When I go to GMpartsdirect 10456288 is for "Manual trans. Thm 700-r4/4l60" and is not right for my truck. Part #104456549 is for "Auto trans. Thm-r2/4l80. 4l60e, electronic" and this is not available at RockAuto

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Originally Posted by dharris894

Nice catch -

Rockauto says that part 10456288 is correct for my truck without saying whether its manual or Auto.

When I go to GMpartsdirect 10456288 is for "[FONT="]Manual trans. Thm 700-r4/4l60" and is not right for my truck. Part #104456549 is for "[/FONT]Auto trans. Thm-r2/4l80. 4l60e, electronic" and this is not available at RockAuto

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You may want to review Rockauto again. It has a listing for both sensors differentiated by the manual and automatic transmissions.