When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
R56 N14 turbo. 171,820miles. New engine at 145miles. Starts no problem but then stumbles and stalls. If driven bucks and has zero power almost like no fuel or massive vacuum leak and can barely move forward.
ZERO CELs. Thats the bizarre part.
I had 4 CELS about 80 miles ago. Nothing since. And the symptoms just started 2 days ago.
Car has new low pressure fuel pump with new engine
New turbo with new engine
new throttle body last year.
2nd OEM high pressure fuel pump has about 50-70k miles.
MAF and temp/pressure sensor post-turbo are original from 2008.
Engine came with new VANOS solenoid.
Changed vacuum tank and lines to turbo wastegate last year.
Testing: BIMMER PROTOOL and eyeballs
Checked for vacuum leaks using brake clean. Especially around the catchcans and tubing. Found nothing.
Cleaned MAF and temp/pressure sensor post Turbo with CRC MAF cleaner and tested for voltage (12 v and 5 volt)
Voltage into and out of MAF is correct but when I tested while revving it stays close to 3volts, doesnt vary much. Cannot find correct voltage in Bentley.
Fuel pressure is 750 psi at rail plus and varies when engine calls for more so I dont think its a fuel delivery issue.
I'm thinking its a MAF issue but I dont know what the readings should be.
Check your VANOS solenoid located passenger side in back of the engine right by the intake manifold and double check your vacuum leaks on the crank case ventilation hose connection that goes into your valve cover
Thanks. I checked all the vacuum hoses. The engine only has 30k miles on it so I doubt it's the vanos solenoid but I'll check that last if the MAF and low pressure fuel pump check out.
What was the source for the "New" engine? Almost sounds to me like the HPFP is not providing appropriate fuel. Can you get a scanner on the car to monitor fuel pressure before and after start? HPFP failure doesn't always generate a DTC.
What was the source for the "New" engine? Almost sounds to me like the HPFP is not providing appropriate fuel. Can you get a scanner on the car to monitor fuel pressure before and after start? HPFP failure doesn't always generate a DTC.
Bought the engine from the dealer.
it's showing 750 to over 1000psi according to bimmer Protoool.
Current hpfp installed at Dealer by last owner 50k miles ago.
Symptoms suggest a fuel supply problem. While the HPFP seems to come in for suspicion the low pressure fuel pump is too often the culprit.
Of course I don't expect you to replace the low pressure fuel pump just on my suspicion. You need a way to confirm the fuel pump is bad. That's hard to do when they fail/act up intermittently.
There is no CEL. Are there any pending error codes? And with a suitable scan tool you could check for any proprietary errors. My experience is often when there is some untoward behavior even with no CEL the engine controller has logged an error code or codes that shed some light on what's going on.
I did. They are posted above. I use Bimmer Protool and Autoenginuity. 80 miles ago it logged MAF errors. It's one of the few engines parts that is original to the car. 176k miles.
I bought a low pressure fuel pump from ecs tuning couple of years ago. I doubt it's bad but I'm gonna check fuel pressure, wire integrity and the relay. I never changed the relay board. It's original.
My 2nd OEM HPFP has about 50k miles on it. I dont think its the culprit as it tracks with desired pressure.
It does jump around about 50 PSI when engine is idling and asking for 750 psi but if I give it throttle it follows the desired pressure. Pelican says 145 PSI is the max variance before you need to suspect the HPFP.
So I did a manual test on the LOW PRESSURE FUEL PUMP with a Harbor Freight MADDOX kit. I used the ends which it claims are for Chrysler and they fit without leaking but I did have to swap the return line tubes . Here is how you do it:
You might be able to use this kit which some guy claimed he used for a Mini 2008 Cooper, as you only need the gauge and one the connectors you see here:
Anyway let the car sit 15-20 minutes so pressure decreases in the fuel rail, then remove the air filter housing (T25 torx) and the disconnect the HPFP hard line (plenty of videos on how to do it) and then disconnect the RETURN line which is easy to find because if you trace the line from the HPFP you just disconnected a foot down youll see how its runs parallel to another line. Thats the return line from the fuel rail. Follow it back up and depress the tab and pull it outwards from the intake manifold so you can twist it around.
The return line sits inside a rubber isolator that slides onto a small metal arm under the intake manifold. PULL IT TOWARDS THE HPFP to free it from the arm so you have better access. You will put it back on that arm afterwards. Circled in red, pic taken from underneath intake manifold.
You press on this tab to disconnect the line. It takes some pushing and pulling but it will come free.
Pic of the ends and descriptions in same color.
This is the adapter installed into the return line and feed line.
And then up to the gauge:
Once its hooked up, start the car 5-6 second and check the pressure, then let it sit for 15 minutes. According to PELICAN Parts guide: Fuel pressure should be 5 bar (72.5 psi). Once you test pressure recharge the fuel system by cycling the key or running the fuel pump. Note the fuel pressure. Then allow the fuel system to sit under pressure for 15 minutes. Pressure should drop no more than 0.5 bar (7.25 PSI) in that time period.
Mine dropped almost 8-10 PSI and then held steady. It never quite reached 72.5 PSI, more like 68-69 PSI but this isnt a high quality gauge so I'm not sweating that.
And ended up at 59ish.
I MIGHT have a faulty check valve on the 5 year old low pressure fuel pump. Its sorta bordeline.
I think I solved the issue. I was getting so many additional CODES from Protools (NONE OF WHICH Autoengintuity could read BTW) it was nuts. Throttle position, MAF, misfired galore, blah blah blah
So I checked for massive vacuum leaks and bad grounds. Took off the intake manifold to check for cracks underneath. Checked PCV lines. I knew my valve cover had been leaking slowly almost immediately after installing new engine (came with the valve cover!) but I ignored it. I even used brake cleaner to try and looks for vacuum leaks but didnt show anything.
I had an updated valve cover from my last engine with only 1000 miles on it so I put it on. Car drives perfect, no error codes, no misfires.
Either I had bad ground or the PEICE OF **** BMW valve cover was leaking after 30k miles.
Fingers crossed this solved it although I'm doubting it.
New valve cover and gasket didn't completely solve the issue. At least is driveable now. Wasnt at all before. Wouldnt even idle for more than 2 minutes. Related? I doubt it. Luck me thinks because am still getting the occasional stumble, hesitation and misfires but no CODES, according to ProTool. Only drove maybe 6 miles.
Spoke to BMW master mechanic and he told me to change the MAF because this Air Mass Sensor Signal error was typical for failing MAFs so I bought a BOSCH unit from FCP Euro and cleared all adaptation but still occasional heavy stumble, hesitation, every few miles.
What to do....drive until I get error codes I guess?
HPFP tracks closely with set pressure value. Dot think its HPFP.
Doesnt mean the fuel pump relay isnt bad. Might be. But the issue is so intermittent I dont know how to test for a bad relay and since I cannot pull it to test it, Im stuck.
Has this resolved your stalling issue? I have the exact problem with mine. Starts perfect even from cold, but after a few seconds starts to stumble and eventually stalls.
Strangely it runs fine with the MAF disconnected (I've replaced that too).
Is the 'upstream' 02 sensor the one on the exhaust just as it leaves the turbo?
Honestly, I don't know for sure. It's kinda crazy. I'm still confused. It started running normally a few startups after I had changed the MAF and leaky valve cover. It was then throwing a code for bad 02, but running ok (although slightly low on power).
After I put the original 02 sensor from 2008 I got no 02 sensor failures.
Note that the 2008 MAF was giving me a sensor signal failure code. A BMW mechanic told me it's very common for the MAF to fail and give that error code.
BTW a bad 02 will not cause an idling car to stall because when the car is idling or at wide open throttle the engine computer isn't referring to the 02 sensor at all.
I had codes for HPFP, but have fitted a replacement and using my scanner the pressure is fine, well over 1000psi.
The odd thing with mine is that when I disconnect the MAF, the idles almost spot on. Plug it back in, it misfires and stalls. Seem to get better the warmer the engine gets. But I don't drive it at the moment, got it as a project and haven't really looked at it for the past month or so, too cold and wet!
Did you check for vacuum leaks with propane? These half baked POS cars have some SKETCHY vacuum lines and a crap valve cover.
Is desired HP fuel tracking with actual HP fuel?
When you turn the engine off and leave the scanner on does pressure stay at around 70psi for 15 minutes (ruling out fuel pump pressure regulator in the gas tank)?
The BMW mechanic also told me that bad ECU/PCM is super common and will cause these issues.
Has around 80k miles on it. Usual history, looks pretty clean and well looked after.
I replaced the main boost hose as that was split around the 'T' off to the valve cover, didn't make any difference..
Replaced the PCV valve in the cam cover too, no change. (mine is an N18).
Scanner reads 72.5psi. Thats after a few mins, but not 15 or so.
I haven't checked for leaks yet. When the weather is a bit better I want to pop the airbox off, check all the hoses, pull the intake manifold too and check for cracks, replace the manifold gaskets etc..
Intake manifold to block seals? No cracks in intake manifold?
Check all your grounds?
Maybe send your computer in for a check...
Need to check PCV lines, and yes, intake manifold to block (not sure if this is a weak point or not, but they are cheap so maybe worth changing anyway).
I haven't actually removed the manifold yet, that's the next job.
Which grounds to I need to check, I saw one on one of the valve cover studs (back of the cover). Are there others?
I think it should be obvious of its cracked. If you use some propane and or water spray it could save you from taking the manifold off. Might explain why it runs better with MAF disconnected.
When you take the manifold off, which I did to check for cracks, look at the intake valves to see if they have ever been cleaned.
Some vacuum leaks, like at the intake manifold can only be found when engine is cold because the heat helps seal the gap.
Some vacuum leaks, like at the intake manifold can only be found when engine is cold because the heat helps seal the gap.
So this is something I was thinking too, as when I got the engine nice and warm after a little 2 min drive around, it was idling a lot better. Still the odd stumble, but no stalling.
