the flyin' scotsman

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?

killav

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.

AO

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.

the flyin' scotsman

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.

blown 87

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.

the flyin' scotsman

Greg I know this is the case for stock eproms but does the same apply for PEMs?

TIA

blown 87

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

sorry about that.

worf928

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.)

Lizard928

They will function exactly the same as factory, in present state.

the flyin' scotsman

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.

AO

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.

the flyin' scotsman

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.