RPM dip and dive
 

Hello,

I have a 2007 E92 with 114k miles on the odo. I recently replaced the plugs around 90k miles..... This week I was on a long (500+ mile) trip and got off the interstate after about 3+ hours of continual driving. While sitting at the light, my car started to shake/shudder and the RPM guage was dipping from it's normal idle of 650rmp to below 500..

The car has never done this before and is fairly well maintained... It occassionally will shake a little just after it's been started especially after sitting all night in the cold.

I know ignition coils should be able to last until ~150k miles, but does anyone think this could be the issue??

Or could it be something like the "winter gas" switch over??

ps... I also use a bottle or two of Techron roughly every 3k miles... last usage probably 2k miles ago.

//Brew

It could be something like....a need to read codes to know where to start.

Do that / have it done; c'mon back....

Yeeeaaahh... I really need to break down and buy me that Bav Tech tool one of these days... I always assume that codes are thrown only when one of the idiot lights shines on the dash, but I know that's not true.

oh well, thanks for the reminder!

114k and you never replaced ignition coil? eventually Check Engine light would come on for misfire code if it's ignition coil, but that should be a permanent rough drive and not come and go.
Perhaps it's related to your spark plugs change.

I cannot help you resolve your issue, and I do wish you luck in figuring out what it was. However, I'd like to say that DSX warned me about the use of Techron, saying something like it is a strong medicine: only use it when you really have a need for it. Therefore, I have no plans to ever use it again, unless someone who knows what they're talking about recommends its use for whatever particular reason that may arise in the future.

What is techtron used for ?

Cleans injectors.

BMW Group Fuel System Cleaner Plus. SI B 13 05 06
PN 82 14 0 413 341

bmwcca.org editor recommends every 3k to 5k miles. I have not used in my car of 134k miles.

Since you are experiencing the problem, try it once.
dump it into an empty tank before filling up

Spend $24 to pull codes: http://www.amazon.com/gp/product/B005NLQAHS

Mine does that at 11K miles. Unsure of the issue; I had guessed at the battery but that seems fine after charging with a CTEK. Current guess is moisture accumulating somewhere

Try cleaning your icv and maf

Oh wait,..., nvm about that!

Pulled the codes... got nothing... No errors have been logged...:dunno:

your comment about moisture makes sense because the last time I had this issue is after I washed my car with a power washer.
Have you learned anything new about his issue.

MiT: No I haven't.... I'm wondering if the battery may be starting to fail? It's still original and I know some days (cold days) it seems to struggle ever so slightly when starting the car...

My driving "pattern" is roughly 2 long (500+ mile) trips per month with a majority of that non-stop giving the battery a good long charge each month... But still, it could finally be starting to show it's age and generating some odd gremlins.

As mentioned above the root cause could one or a combination of many factors. A new battery resolved the same issue in my low mileage car though :thumbup:

Your last walnut shell blast was....was....when?

He has a 328i; a few doses of techron 'should' suffice

Did that read "walnut shell blast?"

Frequently a victim of random hand spasms, I mis-posted. Shoulda read: "Vanos solenoid blast [air]."

Attachment 355041

Was in a pinch at work yesterday and bought a can of compressed air from WalMart.. would have been so much more fun to bring in my Pancake Compressor and use that like I do at home :bigpimp:

I've had issues with faulty IBS (Intelligent Battery Sensor) and low battery in the past, both very bizarre.

IBS failure: RPMs would drop dramatically during cruising as if the car lost electrical. Codes would read faulty Water Pump and IBS in this condition. The faulty water pump code was triggered because it lost electrical power (electric pump). Dealer replaced IBS and all is resolved.

Low battery - the bastard issue to nail down: Subtle rpm dips at idle/cold. HVAC fan would go in and out in really cold or really hot conditions. Yes, HVAC fan. I replaced fan/resistor thinking they were busted, but that was not the problem. Resolved with a new battery, in my case, Interstate Megatron Plus. These issues were resolved by mistake as I normally swap out batteries every 5 years or so I dont get stuck out in the cold.

These cars are dam sensitive to electrical glitches.

Ouch, your pain is felt!

So the conclusion is if your battery is at least three years old and these symptoms appear swap the battery out first. Cheap-ish easy DIY (~$100 from Walmart) that would need doing sooner or later anyway

lol... ah never...

Ahhh now THAT I have had done.. It was at 59,200 on the odo.

OD's now 114K - time for another dose.

Inexpensive multimeter reads battery voltage after lights on awhile.....<12 volts?

http://www.youtube.com/watch?feature=player_embedded&v=m6Y5qXZTPe0


YO! If you got that guy's problem, assault your battery, an inconvenient R&R in the German tradition.

Bavarian Technic scan tool will enable you to register your battery. Among many, many other things....GET ONE.

I LOVE the smell of a DIY on a frosty December morn....

Attachment 355200

.

Good point. I did that with mine and it read low. Exact number is probably in a previous thread. Seems a sensible way to detect batteries like that mine that would charge to the correct voltage but not hold it for long

Ah, found it in the email to a local SA: it measured 11.7 V and indeed needed replacement