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Old 08-22-2019, 05:01 AM
Meenotu2 Meenotu2 is offline
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Mein Auto:
Sudden MPG woes

So, bought the car 2 years ago. Since I've replaced glow plugs and module, harmonic balancer, flushed trans, replaced MAF, replaced all vacuum lines, stage 1 ecu tune, drilled and slotted rotors, ceramic pads, cbu cleaned, and more. All great until I took the D in for a battery cable recall. Even after the tune i was getting 27.9 mpg consistently even 35mph average speed. Had recall performed and now I am at 23.5 mpg. I noticed it immediately after getting the car back. Called the dealer and complained but of course nothing came from that. First just low mpg, then CEL came on. I got a egr temp code, a code that just said throttle, and one that said software reset. Started checking and researching. Thought maybe egr spring was broken but it was not. After a few days I started getting limp mode and had no bottom end turbo. Codes then we're turbo under boost and a couple others. Narrowed it down to vacuum lines and my local import shop replaced them all and that cleared all the codes. Car runs better now than ever but still low mpg. I have used different fueling stations, I always use BP fuel, but nothing is getting my MPG back up. No current CEL but there are 2 shadow codes still coming up when I run a diagnostic. 004687 Throttle and 00AA0E software reset. Once again no CEL. I am running out of ideas. Coolant Temps are right at 90 Celsius so don't think thermostats are bad.

Wondering if the dealer did something software wise that could have affected the tune.

Last edited by Meenotu2; 08-22-2019 at 05:03 AM.
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Old 08-22-2019, 05:50 AM
imtjm imtjm is offline
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Mein Auto: 328ix sdn; M240ix cpe
well, the battery cable has nothing to do with your MPG. which "d"? I believe there is a ELW for egr valve or something like that. check to see if you have an ELW for egr, then take to dealership. simple things like tire pressure. you haven't mentioned much about your vehicle like # miles, type vehicle, etc, so hard to say other than shot gunning it.

you haven't replaced the thermostat, so you it could very well be a failing thermostat
EGR valve leak (like I said, i believe there's an ELW for it on some models)
You didn't mention injectors
You didn't mention O2
You didn't mention NOx sensor
You didn't mention SCR metering valve
Intake manifold leak

on the 335d, the oil pipes for the turbocharger (3 of them) have a tendency to leak, so check those. Also on 335d, the intake manifold charge air line also has a tendency to leak, so check it.

check your dealership invoice to see what they did. If it was just battery cable, there's nothing to do do software wise.

Last edited by imtjm; 08-22-2019 at 05:55 AM.
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Old 08-22-2019, 01:49 PM
Meenotu2 Meenotu2 is offline
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Join Date: Aug 2019
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Mein Auto:
My apologies. 2011 335d 117k miles. I know battery cables don't affect mpg, it's just when it started. The "d" is the car. I don't think it's the tstat due to Temps im getting but maybe. The items mentioned that I have not replaced are due to the fact they have not failed, or at least the car has not thrown a code for them. Intake was removed and replace when the glow plugs and cbu were done. All leak checks were performed when vacuum lines were replaced 2 weeks ago. I will look at the charged air lines and others items mentioned. Tires are brand new Goodyear Eagle Sport.
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