2008 e87 116i n43 HPFP losing pressure under WOT

chflorinn

New Member
Aug 13, 2021
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Hello guys,
I have a 2008 1er e87 116i. Engine code: N43.
The car is losing fuel pressure under WOT, but only up to 3-3.5k rpms.
If I press the gas pedal gently up until 3-3.5k rpms, everything is fine. If I am below 3k rpms and press the gas pedal a little harder or in 'kick down' mode the car starts to struggle. It jitters for a while, it loses power and a strong hissing sounds from under the hood(I guess) appears. If I put the car in neutral in due time(like when the hissing sound starts) and wait a bit, everything comes back to normal. Well, most of the times, cuz there are times when the engine stalls. Also, when this happen, when the hissing sound and the jittering start, the car not only loses power, but there is a strong fuel smell getting inside the car, so I suspect a gas leak, I just can't figure where that might be.
I used INPA and ISTA+ to read live data of my fuel system.

At idle both LPFP and HPFP pressure appeared to be normal.
LPFP: around 5000 hPa(millibar)
HPFP: around 150.000 hPa(millibar)
Also the pressures hold if I'm in neutral, no matter how hard I press the gas pedal.

If the car is in gear(2nd to 6th) however, things are a little different if I go WOT.
LPFP: holds a steady pressure of around 5000 hPa (+/- 1-2%)
HPFP: holds the pressure for a while, there starts to drop under 100.000 hPa. The lower I managed to record was 68.000 hPa. But if this isn't happening the pressure increases up to 200.000 hPa, which is good.

If the car starts to act up and I continue to push it, the CEL comes on and the car starts to shake as if it was running with only 3 cylinders. Until I stop the engine. If I stop the engine, leave it for a few seconds and starts back up, everything comes back to normal. Until I go WOT again.

I also read the error codes almost everytime this happens and the codes I'm getting are as follow:
-2AAF - Fuel pump, plausibility. Integral component EFPPWM outside valid range. Fuel pressure before fuel-supply control valve: around 1500 mbar.
-29D0 - Combustion misfire, cylinder 4
-2A2D - Fuel low-pressure system, fuel pressure. Lower threshold 1 reached.
-29F1 - High pressure sensor faulty, sensor value too low. Rail pressure: 80.000 - 90.000 mbar (depending on the case, but definitely under 100.000)
-3104 - Rough running, stratified-charge mode. Which I don't know what it means.

The things with these errors is that:
-29D0 appear everytime the car acts up.
-3104 only happen from time to time
-and the other never appear simultaneously. It's either 2AAF and/or 2A2D(sometime there's only one of them, sometimes there are both) or 29F1.

The misfire is not happening because of spark plugs or coil packs because they are all new (around 1000 km) .
I already changed the Low pressure fuel sensor. And the Low pressure fuel pump is on the way, I'll change it as soon as it arrives, probably in a couple of days.
I had a guy at a service check my fuel pressure using a manometer a few days ago. For some reason he said he can only check my low pressure side and on the low pressure it was around 5700 mbar. I don't know if it's good or not. Seemed a little too high at the time.

Also, I've got my timing chain kit changed about 5-6k km ago. But that was more than a month ago and the car ran fine. So I think the timing chain can't be at fault here, can it?

I don't know, I'm losing my mind here. I don't know what the cause could be and I kinda don't wanna throw money at my car for nothing.
Do you guys have any idea on what might be the issue here?
Thank you in advance.
 

NoQuarter

Major
Nov 24, 2017
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Indiana, USA
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Z4 35is, 535xi, X5 35i
Maybe a cracked hardline, a fuel fitting not tight enough or the sealing surfaces contaminated? Check each of the injector lines, the fuel rail, etc.

Carry a fire extinguisher šŸ§Æ
 

chflorinn

New Member
Aug 13, 2021
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0
So I come with an update.

The LPFP arrived a couple of days ago and I managed to change it. After I changed it I tried to test the old one just out of curiosity and it seemed faulty. I put it in water and connected a 12v power supply to it, but it seemed to choke from time to time. However this didn't solve my problems, but I think it solved a problem.

After that I went forward and changed the high pressure fuel rail and high pressure fuel sensor, as I suspected some leaking or bad readings that would put my HPFP in limp mode. This didn't help either.

The problems apparently solved after I replaced the HPFP.

I hope this can help someone else who might be going through this.
 

NoQuarter

Major
Nov 24, 2017
1,662
1,066
0
Indiana, USA
Ride
Z4 35is, 535xi, X5 35i
The HPFP turns via the chain driven sprocket and the solinoid valve would just open or close from the 12v.

Not sure what you saw with it in the water?
 

NoGuru

Captain
Jan 9, 2018
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Just North of Detroit
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BMW 335is
EKP could be going bad.

It could be a lot of things really. I think you might just start to throw money at it if you don't take it to a shop to diagnose.
 

Bmwc

New Member
Oct 31, 2021
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So I come with an update.

The LPFP arrived a couple of days ago and I managed to change it. After I changed it I tried to test the old one just out of curiosity and it seemed faulty. I put it in water and connected a 12v power supply to it, but it seemed to choke from time to time. However this didn't solve my problems, but I think it solved a problem.

After that I went forward and changed the high pressure fuel rail and high pressure fuel sensor, as I suspected some leaking or bad readings that would put my HPFP in limp mode. This didn't help either.

The problems apparently solved after I replaced the HPFP.

I hope this can help someone else who might be going through this.
Hpfp replace or lpfp?