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Old 03-25-2011, 09:57 PM   #1
SpanishSubaru
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Join Date: Sep 2010
Chapter/Region: NESIC
Location: Central MA
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2011 BMW 328xi
LeMans Blue

Question New motor wont run?

I just recently finished assembling and installing my built Ej205. Now that the motor is in and everything is buttoned up I can only get the motor to start and the initial combustion completed. It will run at idle from 1k to 2k rpms fluctuating for a bit and then stall out or idle extremely low and rough at like 500rpm then stall.

There is only one CEL on for the front 02 sensor which i have on order but didn't think it would have an effect on the motor starting and running.

The car is on a stock map that was flashed on by the cobb AP when it was unmarried and has aftermarket exhaust, sti top mount.

Anyone have any insight on what i should do/look into to make this thing run correctly past the initial combustion?
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Old 03-25-2011, 10:17 PM   #2
binjoau
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MPS 510 whp GTX35R
Long Rod Motor

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Quote:
Originally Posted by SpanishSubaru View Post
I just recently finished assembling and installing my built Ej205. Now that the motor is in and everything is buttoned up I can only get the motor to start and the initial combustion completed. It will run at idle from 1k to 2k rpms fluctuating for a bit and then stall out or idle extremely low and rough at like 500rpm then stall.

There is only one CEL on for the front 02 sensor which i have on order but didn't think it would have an effect on the motor starting and running.

The car is on a stock map that was flashed on by the cobb AP when it was unmarried and has aftermarket exhaust, sti top mount.

Anyone have any insight on what i should do/look into to make this thing run correctly past the initial combustion?
Maf backwards?
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Old 03-26-2011, 12:07 AM   #3
Crystal_Imprezav
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CGM

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You would be surprised how bad a car can run with a bad front o2 sensor. I highly suggest you avoid running the car until you replace it. You will wash out your cylinders.

Cliff notes: Bad front o2 means your car runs and idles at 10:1 afr's. BAD BAD for a new motor.
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Old 03-26-2011, 04:50 AM   #4
AlaskanProtege
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Really!?
Well as can solve this real fast. (unplug the sensor) how does it run, if the sensor is bad it will run alot better. If the sensor is ok it most Likely won't make a difference.. Hook up a scan tool and watch the 02 swing. It should show a nice pattern if not try added propain or map gas to see if the sensor responds if it does I bet it's ok. (also noting) if a vehicle is in open loop it won't care what that 02 says. And once it sets the light it's already in dummy mode) I would check your mass air flow sensor (or map sensor depending on what ur running I deleate all the maf on my cars and stick to map way more reliable) check fuel pressure too
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Old 03-26-2011, 01:45 PM   #5
SpanishSubaru
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Im off to get the sensor right now, going to plug it in and see if anything changes.

I also forgot to add last night that it seems like im not getting any response to stepping on the gas, when it's idling if i step on the gas then it doesn't seem to rev up, if anything maybe its making it stall??
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Old 03-29-2011, 04:19 PM   #6
soobaviator
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Check da timing...

-soobaviator
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Old 03-29-2011, 04:23 PM   #7
the suicidal eggroll
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Quote:
Originally Posted by SpanishSubaru View Post
Im off to get the sensor right now, going to plug it in and see if anything changes.

I also forgot to add last night that it seems like im not getting any response to stepping on the gas, when it's idling if i step on the gas then it doesn't seem to rev up, if anything maybe its making it stall??
Sounds like the AFR is off

Unplug the front o2 sensor, see if that clears things up.
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Old 03-29-2011, 05:43 PM   #8
project_skyline
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Check for air leaks, timing, and get the front o2 in. Car will run like ass without it.
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Old 03-29-2011, 05:46 PM   #9
the suicidal eggroll
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Quote:
Originally Posted by project_skyline View Post
get the front o2 in. Car will run like ass without it.
No it won't, not unless your MAF or injector scaling are screwed. It will run bad with a malfunctioning o2, but it will run fine without any o2 as long as your MAF/injector scalings are reasonably close.
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Old 03-29-2011, 10:51 PM   #10
jetski247
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its the red shop rag left in the intake.
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