Knock Retard and Low Timing.
Thread Starter
Launching!
Joined: Dec 2001
Posts: 241
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From: Bowling Green, Kentucky
Knock Retard and Low Timing. Last time I A-tap'd my car it was only pulling 21-22 degrees of timing and around 10 degrees of knock. I did the race gas test without A-Tap and the car ran just exactly as it did before with almost exact conditions. Ed Wright did my PCM so should I send it back to him and have him Desensitize my Knock Sensors and bring the timing back up and go back and do another A-Tap reading and make sure? Also how much would this problem hender a car's performance?
TECH Apprentice
Joined: Apr 2002
Posts: 373
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From: Hickory, NC
Re: Knock Retard and Low Timing. Brian...10* of KR is pretty serious. I would try to track down my source of KR before throwing more $$ to Ed. You didn't mention what your Long Term Fuel Trims were (@ idle) nor did you mention anything related to your O2 sensors. I hope you find the problem because that KR is killing your power output. And from my own personal experience, there's a huge difference between say 3.0* of KR and 10.0* of KR.
Re: Knock Retard and Low Timing. 10 Degrees KR! <img border="0" title="" alt="[Eek!]" src="gr_eek2.gif" />
Is this at wide-open throttle? Part throttle KR isn't important. I've never seen more than 4 deg KR at WOT before, on any LS1 vehicle.
Tony
Is this at wide-open throttle? Part throttle KR isn't important. I've never seen more than 4 deg KR at WOT before, on any LS1 vehicle.
Tony
TECH Resident
Joined: Jan 2002
Posts: 754
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From: USA
Re: Knock Retard and Low Timing. </font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Snake Skinner:
<strong>Last time I A-tap'd my car it was only pulling 21-22 degrees of timing and around 10 degrees of knock. I did the race gas test without A-Tap and the car ran just exactly as it did before with almost exact conditions. Ed Wright did my PCM so should I send it back to him and have him Desensitize my Knock Sensors and bring the timing back up and go back and do another A-Tap reading and make sure? Also how much would this problem hender a car's performance?</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">You did not mention if your getting DTC errors and what they are for they would point to the problem. You may find which knock sensor is tripping which would point to the pistons it monitors or the sensor itself has gone bad.
It also could be lousy PCM tuning and instead of properly tuning they shut off all DTCs realted to knock.
Check to see if either sensor is unplugged or the fuse is blown.
Check to see if your getting any misfires and if so is it the same pistons as the knock sensor monitors.
If knock is that high are you hearing it ?
PCM is most likely functioning off the low octane timing table if your only getting about 20 degrees of timing at WOT, should be more like 28 if the PCM tuning was done correctly.
High knock kills performance quite a bit for it forces timing out of the power curve.
<strong>Last time I A-tap'd my car it was only pulling 21-22 degrees of timing and around 10 degrees of knock. I did the race gas test without A-Tap and the car ran just exactly as it did before with almost exact conditions. Ed Wright did my PCM so should I send it back to him and have him Desensitize my Knock Sensors and bring the timing back up and go back and do another A-Tap reading and make sure? Also how much would this problem hender a car's performance?</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">You did not mention if your getting DTC errors and what they are for they would point to the problem. You may find which knock sensor is tripping which would point to the pistons it monitors or the sensor itself has gone bad.
It also could be lousy PCM tuning and instead of properly tuning they shut off all DTCs realted to knock.
Check to see if either sensor is unplugged or the fuse is blown.
Check to see if your getting any misfires and if so is it the same pistons as the knock sensor monitors.
If knock is that high are you hearing it ?
PCM is most likely functioning off the low octane timing table if your only getting about 20 degrees of timing at WOT, should be more like 28 if the PCM tuning was done correctly.
High knock kills performance quite a bit for it forces timing out of the power curve.
