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

Open loop/closed loop question:

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Old Jun 23, 2003 | 10:55 AM
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LWillmann's Avatar
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Open loop/closed loop question:

Does the PCM ignore basically all diagnostic sensors during open loop operation?

Specifically, does it ignore the knock sensor during open loop?
Old Jun 23, 2003 | 10:57 AM
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The only thing that is "ignored" in open loop is the feedback from the O2 sensors. Everything else functions normally. These aren't "diagnostic" sensors.... they are engine mangement sensors and required for the PCM to function.
Old Jun 23, 2003 | 11:21 AM
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I was hoping you might answer Injuneer...

I read your article on the scanmaster and found it to be EXTREMELY informative. Especially considering I am just starting out with Autotap and attempting to track down a knock retard problem that I'm having.

Ok, here's my next question..

If the PCM pays attention to the knock sensor during open loop, then what would cause the first 197 seconds of engine run time, with a couple of WOT runs to show 0 degrees of knock retard. But as soon as the engine run time counter his 198 (mid WOT run as well), it starts showing knock retard.

Any ideas? Of course, I made the mistake of not getting the open/closed loop parameter(if it exists) in Autotap to see if it happened when it switched to closed loop, but 198 seconds is 3 minutes 18 seconds which would make sense for an approx time to switch to closed loop.

Here's the log file I am referencing (if you have time):
Autotap Log

Before logging the file, I had let the engine cool for 2 hours or so, then installed the LT4 KM for testing. Fired up Autotap, started logging (recording), THEN started car, then went driving.

The previous night, I got up to 10.8x degrees of knock on the stock KM, so I put the LT4 in just to test.
Old Jun 24, 2003 | 02:02 PM
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ttt

Anyone???
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