A little scare... :( but ok for now - what's this ???

[Washburn]

Ok the ZHP sits a lot, and last time it got driven was about 1.5 weeks and then the temp dropped, sometimes freezing or below, like last night - car sits outside. Battery is OEM factory.

Today when I started it after sitting for about 1.5 wks, the car started rough, shook, and there was some type of knocking sound with the shaking, as if it idled really slow or something...then the RPMs jumped up and down a bit and then started to drop and then the SES and EML lights came on, and I turned car off - all this was in about 25 sec's or so.

I started it immediately back on, and it started fine, and idled fine, and no SES or EML lamps or any other warnings....

Drove it a bit back and forth - drove like normal, AFA I could tell - normal sounds, normal power, and I shut the car off and on several times during the day while driving, no waring lights, CEL, etc.

Thinking it was the battery perhaps, i went to AAP and had them check the battery (hence my panicky battery thread - i figured it out how to get the cover off - thanks)

- the tech said the battery (OEM white) didn't test good or bad, but 'NEEDS CHARGING' came up on the display of his tester...I didn't charge it - just drove a bit more after that.

They couldn't check codes as they can only do it if the CEL is ON, the tech said...

I didn't get a new battery, as it's still ok...SHOULD I HAVE? I have a $20 off coupon at AAP, and they had the Autocraft Gold 94R in stock...somrtimes it does crank a bit too much before starting, and remote key function have been getting worse...like i have to get really close to open doors, etc...

I don't think the rough starting/idling thing was battery, what do you guys think? if it was the battery, why would the car start at all? and why would the CEL light come on? Bad battery can't trigger a rough idling/knocking and make the SES light come on, right?

On the other hand, if something IS mechanically wrong with the engine, how come it started and drove fine a second later and no CEL any more?

what should I do? a Bit scared right now and bummed...

[danewilson77]

It will be dead next time you drive it most likely.

I vote buy a new battery.

[Washburn]

Thanks Dane .
So a bad battery can cause knocking/shaking and make the SES/EML come on?

I can still get the new battery tonight, I think...

[echo46]

I concur, especially if it is the original battery. It would be about time.

[Johnmadd]

Do you have extra amp and sub or anything extra electronically?

[Washburn]

Nope - all is stock on the car...

so guys - why would a bad battery cause rough idle/knock and SES/EML? but not the battery/charging light to come on? this is what baffles me...

[MrMaico]

Mine has done something similar a few times right after filling gas....it would run rough but blipping the throttle or a restart would clear it out. Never did it once though all last summer and I have no idea what might have caused it.

Another thing I've done a couple of times is started it briefly (a minute or two) not running it long enough for the engine to get anywhere near operating temp and shut down. Then the next time I went to start it, even if it was a week later, it would run pretty rough for maybe 15 seconds or so. I'm guessing it is causing some type of "confusion" in the ECU by not letting it warm up fully before shutting it down similar to what could happen with the automatic choke on a carbureted engine.

Any chance you did this before starting it today?

[kayger12]

Nope - all is stock on the car...

so guys - why would a bad battery cause rough idle/knock and SES/EML? but not the battery/charging light to come on? this is what baffles me...

Yes. Low voltage can wreak havoc on just about everything without throwing a code or triggering the light.

Bimmers are VERY voltage sensitive.

Droid X. Tapatalk. Use it.

[Washburn]

Mine has done something similar a few times right after filling gas....it would run rough but blipping the throttle or a restart would clear it out. Never did it once though all last summer and I have no idea what might have caused it.

Another thing I've done a couple of times is started it briefly (a minute or two) not running it long enough for the engine to get anywhere near operating temp and shut down. Then the next time I went to start it, even if it was a week later, it would run pretty rough for maybe 15 seconds or so. I'm guessing it is causing some type of "confusion" in the ECU by not letting it warm up fully before shutting it down similar to what could happen with the automatic choke on a carbureted engine.

Any chance you did this before starting it today?

- This was not after getting gas. actually it was very LOW on gas...The car sat for about 1.5 weeks before starting today. except: (like you guessed) the following:
- HOWEVER, wifey did start the car just to change the parking spot, about 3 nights ago. Of course I am guessing she shut it down after a minute (max) or so. The outside temps were low then, too.

[MrMaico]

- This was not after getting gas. actually it was very LOW on gas...The car sat for about 1.5 weeks before starting today. except: (like you guessed) the following:
- HOWEVER, wifey did start the car just to change the parking spot, about 3 nights ago. Of course I am guessing she shut it down after a minute (max) or so. The outside temps were low then, too.

I'd bet that's what caused it. I've had it happen twice now. If you have a code reader I'll guess there is a stored code for a misfire. Mine had the code both times it happened without actually lighting a CEL on the dash.

I'd just keep an eye on the battery for now. Maybe throw a charger on it for a while. I thought I might have a bad battery when I had an issue with the low oil light last spring.......now I have a perfectly good BMW battery sitting in the garage.

It was the original though so I'm sure it was getting close to the end of its life.

Barry