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Do PEMs 'learn' engine conditions?

 
Old 10-12-2010, 06:51 PM
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the flyin' scotsman
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Default Do PEMs 'learn' engine conditions?

As we know the stock eproms 'learn' how our engines are running and retain that data unless the batt is disconnected (power is removed from the brains).

does the same apply to the JDS PEMs?

I ask as while still t.shooting my cold idle issues I had a few hours to work on the car yesterday so pulled the fuel rails and injectors, checked all o-rings and carefully rebuilt. When doing this I disconnected the batt. as I normally do when doing big projects.

On restart the stumbling cold idle was worse, the engine would stall unless kept alive with the go pedal so I assume that the PEMs reverted back to the intial program John installs............Jim, Colin, John? anyone?
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Old 10-12-2010, 07:01 PM
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killav
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The info is retained in the PEM's, but the O2 adaptation will be reset with a battery disconnect so the car could run worse for a period of time until it can re-adapt.
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Old 10-12-2010, 07:14 PM
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AO
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Actually, I believe the O2 adaptation information is not a funtion of the PEM or regular chip. IIRC John mentioned that there is some SRAM on the LH that provides this function. Once the LH is disconnected or the battery is disconnected, the stored "learning" goes away and it starts over with the rough idle that eventually smooths out.

However, whatever program was on the PEM should remain intact. If it's stalling, you;ve got other issues or a poor base-line tune.
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Old 10-12-2010, 07:56 PM
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the flyin' scotsman
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thx AO..................I had the cold idle issue previous to this latest work and if I could figure out how to attach my previous post I would.

I believe the intake will have to come off again and see if/where there's an air leak................winter project.
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Old 10-12-2010, 08:13 PM
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On cold start the car will be in open loop and will not take information from the O2 sensor.
Disconnecting the battery will reset the idle adpatation though.
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Old 10-12-2010, 08:23 PM
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the flyin' scotsman
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Greg I know this is the case for stock eproms but does the same apply for PEMs?

TIA
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Old 10-12-2010, 08:33 PM
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Originally Posted by the flyin' scotsman View Post
Greg I know this is the case for stock eproms but does the same apply for PEMs?

TIA
My ability to read has been great lately, my ability to comprehend lately, not so much.

sorry about that.
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Old 10-12-2010, 09:12 PM
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As far as I can remember - not far tonight, perhaps - the PEMs will 'do' o2 loop adaptation, *if* it isn't turned off in the ST UI when you program the PEMs. You can do it either way, IIRC.

In any case, just like a normal LH, one equipped with PEMs will ignore the 02 loop until it gets warmed up, and 02 adaptation will be lost with a battery disconnect.

You can also program the PEMs to ignore the coding plug and to force open loop (in which case there's no adaptation, of course.)
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Old 10-12-2010, 09:45 PM
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They will function exactly the same as factory, in present state.
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Old 10-12-2010, 09:50 PM
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thx Colin, thats what I wanted to hear as I didn't want to think I had introduced another variable with my recent work.

I'm back to finding why its so irratic only when stone cold.............the intake will come off soon.
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Old 10-13-2010, 02:07 AM
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Stock injectors? If larger than stock, the warm up map dumps way too much fuel in to get a nice idle.

If you have the STer, watch the temps on the fuel vs ignition parameters pages. Look far variance. This will indicate an issue with the Temp II sensor.
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Old 10-13-2010, 10:03 AM
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Stock injectors that were cleaned and rebuilt (as much as they can be) a few seasons ago.

I have part ownership of an STII but will wait until I have the intake off and see whats wrong before playing around.
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