how long to idle after battery change?
 

Hi guys, haven't been here in awhile. Still got my Pcar tho! Recently my Yellow top Optima got really weak after 8years. Just got a replacement, but I remember there was a mandatory idle time after fully disconnected battery so the DME can get used to the new battery or so... I want to say it was about 13-15min without blipping the idle?? Anyone know?? I'm pretty sure all electrical/capacitors are fully discharged (small residual spark at positive lead when I accidentally touched positive lead cable to the body when battery completely out).

Oh, my drivetrain is the 993tt with Ruf conversion....

Anyone have the full procedure to make the DME fully properly functional??

thanks a million

Jaime

This may be a "RUF" thing, have had similar discussions on modified OEM ECUs, that need some "drive time" (heard advice like 50 miles, etc.) to relearn the idle / stall limits (Promotive, etc.) lost when battery is disconnected. Not aware of any such need on an OEM 993 TT ECU though. Given battery voltage will fluctuate all the time, can't see the ECU needing to learn a new battery, but a dead battery/loss of voltage could erase idle/throttle/modification memory that then needs to relearn with run time on engine.

Thank you....

Not a Ruf thing. Around 2001 or so I had to replace the entire engine wiring harness. Seems Porsche's old wiring harness was made of some partially organic compound that overtime got brittle and I literally had delaminated sections in my harness, exposing the copper conduction. One day I decided to cleanup my engine compartment with degreaser, rinsed with water. Turns out many of these delaminated sections became Live and energized because of local electrolytic arcing. After cleaning my engine compartment I drove her into my garage (about 10 feet away). An hour or so I re entered the garage to a very strong smell of gasoline! Turns an injector or two continued to be energized and spraying gas into the combustion chambers. When the chambers were full the gas leaked out of the valves and into the exhaust headers and out my exhaust pipe onto the ground (I have no mufflers)!!! I panicked trying to get some air without introducing a spark in the garage! I disconnected the garage door and manually opened the door for fresh air, thankfully my drivers side window was opened, affording me to reach in and put it into neutral, took off parking break and pushed the car out of my garage onto open air, injectors still working and spraying....... I opened the front bonnet and disconnected the battery. Pulled all spark plugs and let it air dry. changed out oil and got her running again once I dried the entire engine bay over a week! Turns out Porsche had/has a campaign to change out the entire harness at a fraction of the price due to this problem. If you purchase the harness by itself its very expensive, but if you look for that special Porsche part number that include a few things including the harness its relatively cheap!

.....anyway, long story short, I remember that "kit" came with instructions about allowing car to idle for "X" amount of time before doing anything. It was for a stock 993tt.

cheers!

Jaime

From '96 Turbo Technic: 250 seconds
https://cimg6.ibsrv.net/gimg/rennlis...88d04cbf51.gif

Could this be what you are thinking? That is giving it time to remeasure all the parameters. This is more for a diagnostics point, don't interrogate the DME (parameters) until after the engine has had a chance to sample all the parameters.

yes. that's looks about right.

thank you!