more difficult to start
 

almost 4 year old vehicle now and a couple times it didn't start up the first try. Didn't sound like it was straining so it shouldn't be a battery issue, although that battery has been going nearly 4 years already. It goes to the point where it's about to turn over then dies. This morning I had to try 4 times (with typical crank sound) before it finally turned over, but right after it still sounded weak for a brief moment. Drove ok, and I had driven it fine for 200mi. this past weekend.

Engine oil level is ok. I checked the manual and spark plugs are supposed to be a 100k mi. replacement item. I'm only at 21k. Yes it's a low mileage vehicle but have done the 3 annual maintenances on time. Any ideas? Gotta get all the wrinkles out before warranty expires in a few months.

As step 1, I'd try one or two treatments of injector cleaner.

I suppose any at the auto store will do? I dont' want to do something that is "BMW-not-recommended" with regard to the internal systems. At least till I clear the warranty phase.

Is it still under warranty? If so take it in.

get your battery checked. i had the same problem in my 05 7 series and it turned out to be the battery. $350 dollar repair btw.

$350 for a battery?!! Ouch! Replacing the battery would be the first thing to try anyway though since most batteries struggle beyond three or four years, especially on low mileage cars. Even if it turns out not to be the problem, you'll likely have to replace the battery soon anyway.

Battery will not be warranted... if you take it to the dealer you will get 'trapped' into the new battery... you'll be on the hook for an hour or two for diagnosis, then whatever they want to bend you over for on the battery.

Battery MAY test good if you go to an autoparts type place, at 4 years I'd just buy a new battery and toss it in- then, if there are still issues go to the dealer.

Remember you'll have to 'register' new battery, i.e. visit a dealer and some $$ anyway.
Re injector cleaners, I'd say any will do it, but get a brand name just for a peace of mind.

FYI- do not automatically assume the dealer needs to do the work. You can buy an AGM, "OE replacement" for much less than the dealer charges....and there are ways other than 'dealer' to access registatoon in needed.

Good discussion:

Battery exploded in my trunk; Please read so this doesn't happen to your E9X. - BMW 3-Series (E90 E92) Forum - E90Post.com

I would still consider the battery, only from firsthand experience.

This Saturday, I went to Danville as a day trip (1 hr steady state drive) and after filling up at a fuel station, the X3 began to have trouble starting. Slow crank, and the DSC + ABS light would illuminate for 2 secs longer before extinguishing. Because this all occurred immediately after filling up, I suspected bad fuel. Battery was #2 on my list but the X3 has been starting fine recently and all had been normal, plus I do mostly highway driving.

I continued my errands, stopping/starting another 5 times, each time with the same symptoms. The X3 carried me home; I'd intended to fix my bad parking job so I tried to start it again but it would not start. Sufficient power to run everything (10 volts) but not enough to crank. Basically the X3's battery gave up the ghost in one of the more convenient places.

I suspect the heat killed the 7,5 year old battery.