I have replied to your questions in blue, within your text.
Originally Posted by
Skysurfer6
I have an 11 BMW 535ix base model that fluctuates in revs upon every start, hot or cold weather. The car has a little over 65k miles on it and has always been thoroughly serviced and mostly at local dealership - not that that is a plus.
No engine light comes on when this happens and I have no OBD that would give me a conclusive answer. Don't even know what the best App is specifically for a BMW.
There are several cheap OBDII options available for sale, that are not specific to Bmw but will do the job in terms of generic codes to be further investigated. This one claims to offer manufacturer specific diagnosis + the ability to customize a few things... https://www.mycarly.com/plan/?c=MA&b=bmw&n=BMW
You can also, for free, install a Bmw software on a laptop, requiring only a cheap ($15) OBDII adapter to connect to the car. Not sure if INPA is compatible with your car as it seems to work up to the E60 5 series, but there probably are other softwares available.
I am up to date on all services required plus new iridium Laser plugs. I also had a Dinan Stage One installed several years ago and a quad exhaust system. I am only mildly increasing the performance of the car to the extent that I am modifying with life enhancing and had mileage saving upgrades.
Two weeks ago I had a VRSF intercooler and aluminum charge pipe installed and am currently looking for the right TDV upgrade compatible with those parts
I can only judge by the gauge but it looks like I am running about 20% cooler. it seems at first, the car was also running significantly smoother too but now I can not tell that much. Maybe I've just gotten use to it.
One thing I do notice is that I don't seem to have the immediate turbo punch I had before the IC and charge pipe were put in. Turbo seems to lag and needs to find a speed at which it will respond impactively.
When upgrading parts related to the intake or exhaust tract, your ECU needs to be tuned accordingly (unless it's a very mild upgrade, in which case it can adapt to the changes) or it will keep trying to run the old parameters, which could explain the turbo lag, either because of increased airflow, or lower intake temps, or both.
Which leads me to a very annoying thing that's been happening for year's. (I have had the car since April of 18 with only one previous owner who put 4k miles on it a year)
So, to reiterate, At every start I have about 15 seconds of up and down revs between 1500 and 500 those 15 seconds could be the time your ECU needs to run adaptations ; sometimes on low end is now a fluttering briefly like it's going to stall. Otherwise, driving and stops at idle are smooth.
I have read the list of things it could be and I am concerned but don't know where to have someone start looking and avoid taking things apart. The cost of testing can be time consuming and expensive and at dealer shop prices, you can easily get jacked around. That cost will be greatly lowered if you get a scanner and look up error codes yourself, to make for a targeted intervention.
What are the easiest things to check that are most obvious without parts replacement and is this problem a common one with this car - even with meticulous maintenance? You could swap the old parts back in temporarily to confirm that they are what is causing the issue. Another thing to look for is a small intake leak (which goes away when the engine warms up, as rubber expands when it warms up) or a MAF sensor issue, but again your best bet is a scanner, not only for this particular issue but on the long run as well.
I would appreciate the best educated advice to a quick fix.
"If you have integrity, nothing else matters. If you don't have integrity, nothing else matters." Alan K. Simpson.
5spd E46 "3XX": 328i engine, 330i Intake and exhaust, CAI, 323i diff.
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