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Old 08-24-2011, 05:33 AM
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Location: DFW
Car: E93 335i
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Default Help on understanding N54 ECU logic

Hi My name is Aaron, my first time on this board, hi to everyone here. Ok so I am working on a N54 engine (08 335i )for my friend , the car have several problem that I am not sure about , I hope you can help me

condition of the car-
it was front ended ( passenger front) so vacuum tank and all the vacuum line are not connected,also the rear intake turbo suction side pipe broke off so it is not connected.

Engine light on

Cylinder pressure test -they are good.

1.)Starting problem
Battery charged up, first try crank over usually no dice, then i let off and try it after 4-5 second again then it will start right up and rough idle fluctuate between 1100rpm and 1400rpm, sometime I may have to try couple of times before it starts.

2.) idle problem

After it start up, the car will idle at 1100rpm to 1400rpm if I put it to drive(D) the car tend to pull forward.

What is PTE heater on the turbo inlet pipe for?
Why there are two pressure sensors one behind throttle body and one in charged pipe? to differential and calculated the pressure differences?

I tried to press on the throttle , the throttle doesn't seem to work even i press the gas pedal all the way down ? could it be the DBW throttle body fail?

is there a such thing ecu safe mode ? if so what exactly it will do to the engine ?

it seem like a vacuum leak to me but it uses map sensor, so shouldn't it just idle very high why is it not stable ? even the turbo inlet pipe disconnected it shouldn't affect idling right?

I can't access to the rear intake pipe to the turbo , are there any way to access to it between take out the head or pull engine?

how likely the intake manifold o-ring (Gasket) fail on these engine?

For some reason I can't use my ebay cheapo OBDII scanner on this car , so I went ahead and bought a BT tools and hopfully I can get an answer on the ecu side but in the mean time I want to see how the stock ECU work so I can understand better to handle this problem.

Thank you in advance

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Old 09-04-2011, 10:42 AM
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2 sensors on throttle to measure air pressure with throttle closed and open, diff as you said. watch high fuel pressure when starting is it good straight away or takes time to build ?
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Old 09-05-2011, 07:40 PM
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Thanx I think it is the timin wheel off bu a bit I need to get the cam align tool do u know where I can get them or rent them?
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