986 S problem at idle, engine won't rev and shakes, battery disconnected - 986 Forum - The Community for Porsche Boxster & Cayman Owners

tony_fury · 11-13-2012, 07:28 AM

While not as experienced as the guy's providing you suggestions.
From reading all the different problems members have encountered on this forum, the number one item that resolves a lot of issues is the MAF.
While also noticing a very low battery will cause some very erratic behavior. If voltage levels are low, sensors can do some strange things.

Reading your post:
The problem started after you disconnected the battery to replaced the dash bulb. I can only assume that the battery was disconnected quite a long time while removing and reinstalling the dash.
My guess is the ECU is having to re-learn all the sensor readings all over again.
You also had the GPS installed for your insurance. (Was this installed after the bulb replacement) (Battery disconnect again?)
You state the GPS was installed on the positive side of your battery, is it drawing from the battery all the time.
(How old is your battery?)

Also reading you stated that after the Indy checked for codes, the car warmed up for half an hour and ran fine.
You have no codes.
I would stop with the 1 minute procedures. Let the car reach operating temperature and re-learn the air/ fuel mixture readings.
Possibly get a volt meter and check the battery voltage after it sits overnight.

My suggestion is to let the car run and warm up, let it re-learn.
Once warm, if it's running fine, take it for a a drive close by and don't baby it.

My 2 cents..
T

Gorthaur · 11-13-2012, 07:45 AM

Quote:

Originally Posted by tony_fury

Reading your post:
The problem started after you disconnected the battery to replaced the dash bulb. I can only assume that the battery was disconnected quite a long time while removing and reinstalling the dash.

Hi Tony and thank you for joining. The battery has been disconnected for 20 hours.

Quote:

My guess is the ECU is having to re-learn all the sensor readings all over again.
You also had the GPS installed for your insurance. (Was this installed after the bulb replacement) (Battery disconnect again?)

GPS installed in April 2012 after battery replacement.

Quote:

You state the GPS was installed on the positive side of your battery, is it drawing from the battery all the time.
(How old is your battery?)

My battery is 6 months old and yes, the GPS is always transmitting.

Quote:

Also reading you stated that after the Indy checked for codes, the car warmed up for half an hour and ran fine.

Yes. But the same didn't happen on the next day.

Quote:

You have no codes.
I would stop with the 1 minute procedures. Let the car reach operating temperature and re-learn the air/ fuel mixture readings.
Possibly get a volt meter and check the battery voltage after it sits overnight.

Overnight the battery is always connected to the smart charger.

Quote:

My suggestion is to let the car run and warm up, let it re-learn.
Once warm, if it's running fine, take it for a a drive close by and don't baby it.

My 2 cents..
T

Thank you again, I will surely try.

Homeboy981 · 11-13-2012, 08:02 AM

May be a bad ground somewhere…possibly that "GPS device" that is not connected to the rest of the car's grounding system, huh? With the ground pulled, you should NOT STILL BE PULLING AMPS from your battery.

My factory stereo experienced similar problems when I replaced the HU and tried to use factory wiring, and original wiring was taken out in favor of wiring I KNEW WAS GROUNDED PROPERLY.

A dead battery or corroded battery posts, faulty ground circuitry, or a MAF about to croak ALL would be producing similar "spotty" problems. Your problem seems intermittent - it does NOT happen ALL the time. The guys have provided AWESOME and CORRECT troubleshooting information, given the responses you have provided.

It may be a job for an experienced mechanic to trace back some of your wires, replace the MAF, replace a faulty battery, clean posts or check the wiring. Batteries DO fail, even new ones. Insurance companies GPSs are made for the masses…how long has that thing been on there?

Your problems, as described, DO NOT seem to 'go by the book' of troubleshooting….unless some bit of information eludes us!

LOOK HARDER you will find a bad ground, visually check the MAF - clean it with MAF cleaner, clean the battery terminals (even IF you have a new battery there can still be crud on the posts-check it).

Your answer lies within. If not, there is no shame in going to the Indy (would not trust the dealer) and have him try 'specific' items, as described.

Good Luck!

Gorthaur · 11-13-2012, 08:15 AM

Homeboy... thank you!

Maybe there's something more. When I was about to reconnect the negative cable, I incidentally dropped the hexagonal nut which allows the end of the cable to embrace the battery pole. I tried to find it but I didn't make it, so I used another hexagonal nut which seemed to fit perfectly even though it had a different outer size. Perhaps the problem lies there, and since I went to the dep to buy the nut of the right size, this evening I'll be able to throw it in while reconnecting the battery. I will record a video as well and hopefully I'll show it to you.

Gorthaur · 11-13-2012, 08:59 AM

Quote:

Originally Posted by Homeboy981

May be a bad ground somewhere…possibly that "GPS device" that is not connected to the rest of the car's grounding system, huh? With the ground pulled, you should NOT STILL BE PULLING AMPS from your battery.

The GPS device is not connected to the rest of the car's grounding system, as far as I know. Later I will post some pics.

Thanks!