Part throttle pinging with LTerms at 0. Help.
Thread Starter
Staging Lane
Joined: Nov 2001
Posts: 77
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From: Phoenix Arizona
Part throttle pinging with LTerms at 0. Help. Ok I’ve done extensive Ataping of my car to gather data to look at. While doing normal crusing between 40 and 50 MPH in 5th gear (M6) my LTerms are anywhere from -1.6 to +7.8. It all depends on what % my throttle is at. 99% of the time my LTerms are at -0.8 to +0.8. If I understand the MAF tables and LTerms correctly this is all pretty good. Why do I have a part throttle pinging problem then? It happens just at the point of adding throttle slightly without changing gears. It’s very audible, and A-tap can show as much as 5 degrees of KR. I’m using the best gas I can find here in Phoenix. It’s only 91, but I can’t find any better. Just as a test I dumped a can of NOS Off-Road Octane Booster in the car and the problem got much better. I still had some pinging, but not nearly as bad. My compression is around 10.5:1 and I’m running with a 218/218 .527/.527 112LSA cam from MMS. If I adjust the MAF tables up say about 2 to 3% would that help any? Since the PCM is in closed loop won’t it just pull the extra fuel back out because of the feedback from the O2 sensors? Can I adjust the Stoich Ratio down to 14.4421 (about 2% richer) to help at part throttle? Any help will be appreciated.
Thanks.
Tim in Phoenix AZ
Thanks.
Tim in Phoenix AZ
Thread Starter
Staging Lane
Joined: Nov 2001
Posts: 77
Likes: 0
From: Phoenix Arizona
Re: Part throttle pinging with LTerms at 0. Help. </font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Sparky:
<strong>Chris:
Do you think he could have a carbon buildup causing the problem at that point?</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">I was thinking that too. I've never run the GM Top Engine Cleaner. I was thinking about doing it, but my neighbors would have a fit. I guess I could always do it at 2am or something. One thing I didn’t mention above is this problem does NOT show itself when the engine is cold. My morning commute to work is ping free, but the drive home with 90+ degrees out side is ping city.
<small>[ April 02, 2002, 09:02 AM: Message edited by: Tim98Z28 ]</small>
<strong>Chris:
Do you think he could have a carbon buildup causing the problem at that point?</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">I was thinking that too. I've never run the GM Top Engine Cleaner. I was thinking about doing it, but my neighbors would have a fit. I guess I could always do it at 2am or something. One thing I didn’t mention above is this problem does NOT show itself when the engine is cold. My morning commute to work is ping free, but the drive home with 90+ degrees out side is ping city.
<small>[ April 02, 2002, 09:02 AM: Message edited by: Tim98Z28 ]</small>
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Re: Part throttle pinging with LTerms at 0. Help. Have you lowered the fan settings to drop the over all engine temp? 160 deg theromstat? May be you can block of the air inlet if you are running a cold air kit. The hot air in Tx is the devil unless your running real fat. Top cleaning should make all the difference if you have done the pcv mod to eliminate burning the recirculated air/oil mixture. I'd do that first. Good luck!
Re: Part throttle pinging with LTerms at 0. Help. When the engine is cold you may be running a richer mixture and your intake charge is probably cooler and less prone to detonate.
