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2Addicts | BMW 2-Series forum Technical Topics N55 (M235i) Engine, Transmission, Exhaust, Tuning Car Burned through Half a tank of gas in 20 Miles!!!

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      01-16-2021, 06:50 PM   #1
i6_Steve
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Car Burned through Half a tank of gas in 20 Miles!!!

So For a month I've been having some random idling problems that would go away after the car warmed up a little. I got an lean error code in bank 1 after a few days, I looked for Vacuum leaks and could not find any even tried the brake cleaner trick. Next I thought my injectors might be a bit dirty so I used a fuel injector cleaner, the car worked great for the first 1/2 tank.

Then after a WOT pull the car started running really rough I pulled over and the car was shaking and sounded like it was running on 3 cylinders I saw white smoke coming out of the exhaust and confirmed it was burning fuel.

The only codes I saw were the same lean code and an O2 Sensor code for bank 1 the car kept stalling and driving super rough but I decided to drive it home a 20 mile drive I left the spot with a little under half a tank and it burned all of it by the time I got home.

I pulled out the spark plugs and one was drenched in fuel another 2 had the smell and 3 looked to be fine.

I'm thinking it's the injectors however I know that's not a problem with these Engines and input would be appreciated

( Car is FBO upgraded HP and LP Fuel pumps had a custom E-85 map and had upgraded Spark plugs)
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      01-16-2021, 07:29 PM   #2
XutvJet
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Injectors are good starting point. However, you've modified all the fuel pumps, are running ethanol, and obviously have lots of power bolt-ons and pushing that N55 extremely hard. It's going to be very hard to trouble shoot this and is the downside to pushing these motor beyond Stage 2 with pump gas. You'll like need to involve a tuner and tech to troubleshoot and get to the source. My guess is it's the fuel pumps and E-85 that wrecked the injectors. Basically pushed them too hard. Are you running straight E-85? If so, that's a big no-no in these cars. E40 is as far as you want to go.
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      02-13-2021, 02:52 PM   #3
n55d_more_alpine
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I had a very similar problem as you described. I have a catless downpipe and tune and It ended up being that the pre cat O2 sensor wire had been cut through due to rubbing on the engine cover. Ended up replacing the sensor and all my problems went away. Before I had the O2 sensor replaced it would judder horribly after medium to hard acceleration and I was forced to pull over and restart the car. Also it was burning fuel like crazy and would backfire extremely loud.
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      02-17-2021, 02:28 PM   #4
mikeysosa
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Xutvjet is right, you need to check your injectors, fuel pumps, and ESPECIALLY your fuel regulator. The fuel regulator, when it goes bad, can simply dump fuel into the system and cause a problem like you described. It can also do the exact opposite and run too lean. I would check it out. If that's the problem, a new one is $150 on FCP Euro. Hope this helps!
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