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RPM dip and dive

6K views 24 replies 8 participants last post by  MP3_E46 
#1 ·
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
 
#2 ·
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.
It could be something like....a need to read codes to know where to start.

Do that / have it done; c'mon back....
 
#3 ·
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!
 
#4 ·
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.
 
#5 ·
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.
 
#8 ·
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
 
#9 · (Edited)
Spend $24 to pull codes: http://www.amazon.com/gp/product/B005NLQAHS

Hello,It occassionally will shake a little just after it's been started especially after sitting all night in the cold.
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
 
#14 ·
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.
 
#15 ·
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:
 
#20 · (Edited)
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.
 
#21 ·
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
 
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