[M//SPORT]

More of the same sorry guys.

Bought a 2008 e92 n53, 325i aka 3.0, from a lying cop who hid the issues, arse.

Anyway am left with issues, very like the issues many get, wonder if anyone can offer some help as its doing my head in now.

Same old cold starts, ok after warmed, runs fine smooth as. I have used Bimmerprofs diagnosis process as i am getting the Nox sensor codes ( short circuit, etc ), misfires, mixture codes etc, high mpg, smell of fuel on cold start. black tail pipes and obvious unburt fuel from pipes.

The nox sensors looks dead, as per Bimmerprofs and INPA, so recon its had a fuel bath, but o2s are ok apart from reading rich bank 1.

My other issue was i found a large crack near the oil filler cap neck ( common issue ) so big vacuum leak, i sealed it for now and did help with mixture. This is about to be replaced not cheap.

Trims, o2 readings started looking better but bank 1 was high before this, still is a little. Nox still dead.

Checked the plugs after an overnight soak, bank 2 good bank 1 sooted , too rich deposits ( black ) but no sign of wet plug/s though, if they are sooted then surely so are the injectors, been told this is not a true indication of bad injectors as they can also have bad spray patterns or clogged so no fail safe way of telling just by a plug pull. How do you check on INPA, i cant find it ? dont wana start shutting down cylinders.

Coils ok, and changed plugs, still no better.

So was away to swap my Nox sensor out with the NOXEM Bimmerprofs model, and replace valve cover and gasket for BMWoem as after the temp repair on the valve cover things improved with mixture so kinda blamed the Nox sensor because of the constant Nox codes ( no cat codes yet ).

But now i aint so sure.

Obviously the valve cover etc, would have been causing a huge intake leak, possibly triggering the Nox and o2 sensors to then send more fuel, putting pressure on the HPFP the injectors etc, in a self perpetuating circle to foul plugs, Nox, O2s round and round it goes until Nox is dead and maybe injectors to a point.

Anyway i am stuck what to fix obviously the valve cover is a defo, BMW want over £900, supply is a shade over £400.

The NOXEM is £330 delivered if i really do need it.

And as i am sure most of you know injectors per bank supply are about £550-600.

In an ideal world change them all at once, but i can really only afford 2 at the mo, so really at the end of the day its the choice after the valve cover of Nox or injectors but which, frying my head........looks like Nox all day long, INPA pings the Nox right away, its got short circut codes , and many others, looks obvious but i aint too sure to be fair. Have rea conflicting reports that the Nox would cause misfires and poor cold start and idle and others saying not a chance. mMy understanding is the Nox cant sent anything until warmed up regardless if working or not, but car could be running on the stored long term and short term fuel trims by default.

After the valve cover gasket including cracked cover, what should i change first, injectors or Nox, i am totally lost as i am sure most that have suffered these issues have been. There is a wealth of info online but there is also alot of conflict too.

Also i aint sure if anyone can answer this one, when these cars start playing up, is it the faulty Nox codes that causes it to run a high mpg because not in stratified mode, or is it the injectors blowing so much fuel threw, obviously if there is an air vacuum leak this wont help but take that out of the equation. Which would cause the bigger fuel dump anyone ???

I have read alot about these cars over the last while, and have worked on the e39s and e46 model but ths is a different animal altogether, help.................

[M//SPORT]

Also my understanding of the Nox sensor is.... if its faulty with no signal to the ecu, will not relay it back to the ecu to allow correcting of long and short term fuel trim, this is especially bad if the car has been running like this for a while as will just use the historic fuel trim levels.



So surely this must affect the cold start and potentially cause misfires too.

Or is it the job of the precat o2s info only, sent to the ecu that affects the mixture, air /fuel mix.

There is so much conflicting info, so say yes some say no.........

http://eleganz-durch-technik.blogspo...placement.html

What does a NOX sensor do?

In a NOX sensor, the NOX is separated into nitrogen and oxygen by a catalytically active electrode.
The amount of oxygen is measured in the same way as with a broadband or linear lambda sensor.
HOW DOES AN NOX SENSOR WORK?

The NOX sensor has two rooms. In the first chamber (which resembles that of a broadband sensor) the oxygen content in the exhaust gas is maintained at approximately 10 ppm by means of a so-called pump flow. The power required for this is inversely proportional to the air-fuel ratio and can be used to correct the NOX signal depending on the measured air-fuel ratio. In the second chamber, the NOX reaction, the separation in nitrogen and oxygen, takes place. The current required to keep the environment of the platinum-rhodium electrode oxygen-free is proportional to the NOX concentration and thus provides the measuring signal.
Why is a NOX sensor used?

Because the engine is directly injected and the combustion is proportionally hotter than with ordinary engines, more NOX is produced than is permitted for the type approval for Europe.

What's going wrong?

Because the NOX sensor has a limited life span, it will sooner or later break down. If the signal from the NOX sensor no longer falls within a certain bandwidth, the engine control unit will store a malfunction which causes the engine to enter an emergency run where fuel consumption increases and the engine will stall slightly. The engine failure light will also light up. In many cases the NOX sensor is broken.

[M//SPORT]

ouch expensive day today, just bought from BMW brand new rocker/valve cover with gasket, bolts etc got a discount usually about £400 got for £350. May fit it myself, the older BMWs were a lot easier, my local BMW indy all ex BM guys are gona give me a price fitted. Anyone know the book time on this, cant see being any longer than 3 hrs tbh ?.

Then bought the injector puller with multiple sizes, the E torks multiple, and of course the 3, 13537589048, index 11 injectors, got them from Harry Fairburn on a special £184 each best price i could find anywhere that includes from Merlin whom at the moment from memory are £198 same exact injectors. Price for 3 deliverd with a 2 year warranty= £552.

Will hold off on the Noxem which if the codes dont clear and the reading on INPA dont improve will buy at £330 delivered, fingers crossed this car is costing and only just got it.

I believe in karma and hope it bites the last owner firmly on the ass, prick lol.

[W37V]

Sorry many of us here can't help you. This forum is mostly people from North America, where N53 was never offered. We got N52 and N51. Since N53 is close to N54 in regards to fuel injection etc, you should check what kind of ailments it has and work from there.

I do think that N53 suffers from carbon build up, just like any other direct injected engines, as well as faulty injectors, bad hpfp, etc. Carbon build up can cause bunch of issues, so if you are handy, you should consider doing walnut blasting or similar. Also, while you are at it, just swap your intake from single stage to 3 stage manifold for some extra hp (330i hp). If you have carbon build up, you might be better off swapping intake anyways.

Good luck with everything.

[M//SPORT]

all fixed.

[CTinline-six]

Originally Posted by M//SPORT

all fixed.

What was the cause?

It might help others who search this thread looking for a solution to the same problem.

[moiz]

Originally Posted by M//SPORT

all fixed.

Hi, did you end up fixing the nox? Was that the main culprit if the low mpg? Asking because my mpgs low and ive just changed all injectors to 11 and still bad mpg. Thanks

[0l0dom0l0]

Bad nox is the no1 source of poor mpg and running issues on the N53.