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Low idling RPMs and fluctuating MPG gauge

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Hey guys -

This is an exact copy and paste of my post on I'm looking for some serious advice.

Disclaimer: Assume that I am car-illiterate. Damn close to it.

A little background: 2004 330xi, about 104k miles, and just had a lot of work done to it.
About a month ago, my SES light came on and I noticed that my idling RPMs were really low, chugging and fluctuating like the point that I really didn't want to drive it out of fear of what was coming next.

I brought it in to a local shop and they did this (word for word on the receipt): "Checked computer functions, checked codes & data, has code P0300, P0301, P0302, P0303, P0304, P0305 all misfire codes, P0171, P0174 both lean mixture codes, checked & cleaned mass air flow censor, replaced air filter & spark plugs, cleared codes & test drive"

I got the car back and it ran fine for about two days before the same problems returned and I brought it back to them.

My next receipt reads: "Checked codes & data, system too leak, fuel pressure in specs, mass air flow censor out of specs, oxygen censor out of specs, replaced mass air flow censor & crank case vent valve & hoses, replace fuel filter, cleared codes, no codes came back but not completely correct, check & replaced DISA valve (anti diesel valve) flapper broken so computer could not shut it off after starting".

I've had it back in my possession since February 5th. It was running fine until about 5 days ago I noticed that my MPG gauge is either ridiculously delayed or inaccurate. When I accelerate and drive, even just up to 20-25 MPH, the MPG gauge stays stuck all the way to the right (12 MPG). It only moves left when my foot is off the gas and coasting. Now I completely understand that when you accelerate, you use more fuel and your MPG's goes down but this is very noticeably off and had just started acting up recently. Also, my idling RPMs have dropped back down to just over 500 which is back to where it was when I originally brought it in to the garage.

Any input at all is greatly appreciated. I just need to know if this is something I should have looked at again ASAP because I have a 300 mile drive coming up in two weeks that I need to be able to make.

I can post a video of the dash when driving if that would help.

TL;DR Had a lot of work done to my e46, low RPM's and messed up MPG gauge as a result
1 - 7 of 7 Posts
So your Anti Diesel valve was replaced ? lol
Maybe check your car for vacuum leaks?
Like I said, I only know the basics of car care. Oil, tires, etc. lol But that is what the old lady who typed up my receipt put on there. I'm in southern Indiana without a BMW dealership for 60 miles so I gotta work with what I have.
From what I read before I also assumed it was a vacuum leak.
It sounds like the shop that you went o already replaced lots of parts, how much have you spent on part and labor? Do you know for a fact that your DISA valve has been replaced? Does your receipt shows a break down of the parts that was replaced? It seems strange to me that your car will run fine for a couple of days and then go back to not running fine.
Yes they actually showed me the old DISA valve and that thing was corroded with black not moving
1 - 7 of 7 Posts
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