LT1 Based Engine Tech 1993-1997 LT1/LT4 Engine Related

Pulling timing for no reason?

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Old Jun 2, 2013 | 07:06 PM
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94Form's Avatar
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Pulling timing for no reason?

Having a couple problems I think according to datamaster. Problem number one is it is pulling up to 5* of timing under load with no knock counts.

Problem number two is long term fuel trims are usually around 150, except the exhaust smells like it is running rich. Also the long term doesn't seem to be corresponding with the short term. I can watch the short term stay around 130 and the long term will continue to rise...

Any help would be appreciated. Is there anymore data that would be useful here?
Old Jun 2, 2013 | 08:50 PM
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Re: Pulling timing for no reason?

If you can post a log that would be helpful.
Old Jun 2, 2013 | 09:33 PM
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Re: Pulling timing for no reason?

Originally Posted by 97WS6SCharged
If you can post a log that would be helpful.
https://www.dropbox.com/s/3znlat2wrk...h_acel_eng.uni
Heres the log, hope somebody can take a look and help me out. Only time I had knock count was if I tried to cruise in the range of 1000-1100 RPM.

Last edited by 94Form; Jun 2, 2013 at 09:37 PM.
Old Jun 3, 2013 | 05:27 AM
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Re: Pulling timing for no reason?

The PCM can pull timing for two reasons - 1) if it detects knock via the knock sensor. The knock count will not necessarily increase. 2) if the PCM sees combinations of engine operating conditions that MAY cause knock. That's when knock count seems to increase. And it generally will not pull timing when knock count increases, unless there has been some evidence of actual knock being detected by the knock sensor.

It will also pull timing almost constantly if you have a trouble code for the knock sensor.
Old Jun 3, 2013 | 11:07 AM
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Re: Pulling timing for no reason?

Originally Posted by Injuneer
The PCM can pull timing for two reasons - 1) if it detects knock via the knock sensor. The knock count will not necessarily increase. 2) if the PCM sees combinations of engine operating conditions that MAY cause knock. That's when knock count seems to increase. And it generally will not pull timing when knock count increases, unless there has been some evidence of actual knock being detected by the knock sensor.

It will also pull timing almost constantly if you have a trouble code for the knock sensor.
Thanks for the response. Went back to look around and see if anything was touching to cause real knock (even though I can't hear anything). And I found this...
Name:  20130603_105125_zps464a047a.jpg
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Size:  56.6 KB

This is the passenger side transmission flange. I'm going to hope and assume that this is what is setting the knock sensor off. It seems to me that I would be able to shave a little off that flange to where it isn't touching the header. Or would that not be wise?

Last edited by 94Form; Jun 3, 2013 at 11:09 AM.
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