Engine misfires and weak battery

[klargo]

I just wanted to share my experience with my 2013 X5 E70 that has approx 69000 miles on it,believe it or not this is a true story. I started getting intermittent check engine light and codes with misfires on cyl 3 and 5 along with multiple cylinder misfires codes about 3 months ago. I also had a noticable but slight bump in idle when starting car cold in colder weather. I swapped coils around but issue stayed with 3 and 5 cyl. I inspected fuel injectors and found 3 and 5 to be really wet with fuel so I thought I found the culprit (leaky injectors causing rich start) and ordered new aftermarket Bosch injectors and changed them. I had the battery on a remote charger during the time I changed injectors. Afterwards car ran great I patted myself on the back for such great mechanic skills. After about a month of my wife driving to work and back (5 miles each way) the CE light came on with same codes along with new code low voltage reading to sunroof module. After some brainstorming I started thinking about battery being weak especially in cold weather . I ordered a scanner that performs battery maintenance check on BMWs to check battery status and found battery was original and had fluctuated in charge from 40 to 75 percent charge over previous 10 days and at one point was down to 25%, the current charge was showing 11.8 v with eng off. Since this was supposedly the original battery (approx 8 yo) I decided to change it. Dealer wanted approx $650 for battery and work so I bought a Diehard group 9h, 950cca, 190 ra, 100 amp hr battery which is same size and rated almost identical to the installed BMW battery (same except BMW was 105 amp hr). Got it from local Advance store for approx $250. Changed battery a month and 1/2 ago. I was able to register it in ECM with my Autophix 7910 scanner but unable to recode ecm with new amphr rating of 100 vs 105. Hopefully not a huge issue. Anyway the results were amazing! No more rough idle on start up, its been a month and half with no engine light, and car just seems to perform better all in all! There was no evidence of a weak battery car always started right up and I never would have known had I not used a scanner to check condition of battery. Now the battery is at 12.4 v with car eng off and charge state history never goes below 75% according to scanner histogram. The car idles great even when cold no more bumps in the idle. Thats my story, first time I ever experienced weak battery causing issues like this just thought I'd share in case it might prevent someone else from rushing off and changing fuel injectors and such before checking battery.

[randrews15]

Weak or dying batteries are notorious for throwing all sorts of codes and causing issues. Eight years is a good run for that battery for certain.

[klargo]

Yea I'm learning more and more about BMW peculiarities and collecting more special tools than I care to just to avoid dealership. Also thankful for sites like these and youtube since its very difficult to get any maintenance info from BMW without paying through the nose. Never heard of a registration requirement to reset ECM after battery change but glad I found that info on the net as well.

[ryansbmw]

Mind linking the tool you used to monitor the battery voltage?

[Thecastle]

Car batteries (lead acid) lasting 8 years is pretty darn miraculous. The hotter the climate the shorter the life and if you run it down to dead, your really shortening the life of the battery. I pretty much replace mine every 4 years to keep the cars healthy. I've had them go bad in as little as 3 years in Houston on a VW GTI. 4+ years and your generally on borrowed time in hot climates. I wouldn't go more than 3 years on a V8 BMW without replacing the battery. N63's eat them in less than 2 years if you don't keep them on a battery charger, weekly

https://www.roadandtrack.com/car-cul...ns-bmw-n63-v8/

[klargo]

The scanner I bought was Autophix 7910 off Amazon. I actually bought it to read codes and register/recode fuel injectors and battery. It does a good job reading codes but would not code new fuel injectors (couldn't communicate with ECM for some reason) and customer service wa unable to resolve issue. It has a function for battery maintenance where it can determine current state and a histogram of charge state from last 10 days. It also allows the battery to be registered (old battery values reset in ECM) which supposidly is neccesary to make sure new battery isn't charged at too high a rate which can cause damage to charging system and new battery over time. The scanner doesn't have a function to "code" or reenter new battery values to ECM but this is only necessary if changing from AGM to lead acid or different Amp hour/CCA values. I found identical Group 9h AGM Diehard battery with exception of Amp hr its 100 vs the original 105 AH so I'm hoping not a huge issue. I guess the regstation process worked cause afterwards the scanner reflected 1st battery replacement at 0 miliage 2nd battery replacement at current miliage of 69k. I also noticed (via hand held meter) that the alternator was charging at 15.8 v (not good) prior to battery replacement and now it hovers at 14v with car running and all acc off. After soem research I bought an AUTEL AP 200 bluetooth scanner off Amazon to code my new fuel injectors it worked great for that but was a learning process that required patience to download several programs to phone. The newer Autel versions claim to register and recode BMW FI and Batt but my old version was unable to do anything with Batt. I suggest read reviews from Amazon on scanners to hopefully verify if it does what you are looking for.

[klargo]

And by the way newer BMWs and other cars have AGM (Absorbed Glass Matt) batterys not Lead Acid. The are designed to last longer than Lead Acid and run high demand electronics and things such as elec seats,warmers, sunroofs, mirrors, etc that most cars have today. If you changed an AGM battery to a lead acid that could be why your only getting 3 years out of them and need to charge all the time although I agree I was lucky to get 8 even out of AGM they have life sxp of 5-6 y.