Hi all, I’m a long time lurker, but my first post.

I’ve recently purchased a little 2011 R57 (N18) project for winter, but this fault has me stumped!

The engine starts on the button, when cold or warm, even if left for a week. But almost immediately it starts to idle really rough and most of the time will stall. Hitting the start button again it will fire up straight away, but still run rough.
If I get the engine nice and warm by blipping the throttle, it will idle much better, still not ‘perfect’, but almost.
If while the engine is cold and running rough, I disconnect the MAF sensor, the idle settles and it will not jump or stall. Plugging it back in just makes it run rough again.

I was initially getting 2C01 code, HPF Pressure too low (Fuel Rail pressure), but since clearing the code it hasn’t reappeared.
Im getting no stored codes, but if left idling long enough I get the half engine light appear (limp mode?).

So, I’ve replaced the MAF sensor, still the same issue.
Had the HPFP refurbished, it’s reading over 1000psi at idle, but goes up and down as the revs rise and fall at idle. (LPFP shows 72.5 psi).
Replaced the coils and spark plugs.
Replaced the PCV valve.

Next on my list is to remove the air box and inlet manifold, check the associated hoses and replace the rubber manifold seals.

I might also change the VANOS valve(s) too.

Does anyone recognise these symptoms, or experienced them? Anyone have any thoughts on what else I could look for or check?

Apologies for the long first post, I’ve searched these forums and seen almost identical problems, most of which point to the HPFP, but mine appears to be putting out correct pressure, and starts on the button every time.

Any idea are welcome.

 

Your symptoms sound exactly like a failing high pressure fuel pump. If you are getting 2C01 even after the fuel pump refurb, the fuel pump will need to be replaced with a quality new unit. The service plan for that code is either low fuel in the tank, or bad high pressure pump. I've seen too many reports of cheap or refurb high pressure pumps just not operating right.

 

I haven’t seen the fault code come back since having the pump refurbished, also the pressure looks ok.

I am still thinking there may be something still wrong with the pump, but it’s an expensive thing to buy if it doesn’t turn out to be the problem.

 

Also, if it was a failing hpfp, why would disconnecting the MAF sensor instantly smooth out the idle and stop it stalling?
That’s the bit I’m struggling to understand.

I believe disconnecting the MAF puts the ecu in to a default map, but I can’t see how that would affect the fuel pressure?

 

You are probably correct about that point... I would clear all stored codes, then drive it for a few days to see if any new ones get stored.

 

I’ve just fitted a known good HPFP from an engine that was running fine. Still getting the same issue. Revs try to settle after starting the car and then it splutters and stalls after a couple of seconds.

Hopefully the link below works that shows what happens.

https://1drv.ms/v/s!AheX6RRKMK0CgbdEziktjgGNfBct6A

 

You might want to look into this…

also, get in touch with these guys, they can fix this if it is your issue.

www.ecumaverick.com

 

Hi,
Thanks for posting up the video, interesting watch. Sadly that isn’t the same fault I have.

Mine had a lumpy idle and stalling, it doesn’t just cut out.

 

Hi All,

After a cold and wet few months I'm picking this back up now I'm able to get outside to work on the car. Still having issues sadly...

In addition to what I've tried above, I have now also...
Replaced both VANOS valves (intake was all gunked up)..
Removed and checked the intake manifold (looks ok, can't see any split or broken hoses)..
Replaced intake manifold runner seals..

Car still starts straight away, but immediately the rev's stumble and car eventually stalls, but only when cold. Once the engine has warmed up for a few mins of gentle rev'ing to stop it stalling, it will idle, but keeps going in to limp mode.
The following errors are appearing (but with no MIL light)..

2BC0 - Mixture Control: Fuel Air Mixture Too Lean
36C5 - DME Internal Fault: Monitoring Plausibility of Mixture Correction Factors

I have noticed while monitoring the live data that the 'Fuel Quality Control Valve' value is around 25%+

Starting to feel like I'm losing this battle, but at the same time I think it's going to be something obvious! (I hope).

Can anyone offer any more idea of what I could check/test/try?

Thanks all.