Car goes into lower RPMs and stalls

[Leafsrule531]

I have symptoms of possibly a bad fuel pump. There are times when I turn the ignition and it cranks but no start. Then I wait a few seconds and do it again And car turns on fine. The other day I was driving and I took a turn in 2nd gear and realized the car turned off while the clutch was pressed down. Now it’s doing it way more often when the car is running in slow speeds it just turns off but turns back on when I try again.

My guess is my fuel pump went bad but are there any codes that come up when the fuel pump is bad ? I will go home and run the codes and post them here.

Additionally, is the genuine bmw pump the only option we have which is what I see on fcp ? It’s $500 which is ridiculous. Any decent aftermarket options if I do have to replace it?

[zzyzx85]

Can't help with the diagnosing part but there's the Radium fuel pump "adapter" that fits aftermarket fuel pumps in the space of the factory one. http://www.radiumauto.com/Fuel-Pump-...BMW-P2087.aspx

[undyroos]

I was having similar symptoms as you, car stalling as it was coming to a stop with the clutch pressed down. Since I'm at 137,xxx, I replaced both intake and exhaust camshaft position sensors, the two engine side throttle position sensors, cleaned the ITBs and ICV, and replaced the fuel filter. Still experiencing an idle drop/stumble when coming to stop with the clutch down but not to the point of stalling out. Also considered my fuel pump was dying so I got the Delphi FG1659 from RockAuto for $350 per https://www.e46fanatics.com/threads/...ement.1305176/ which is a steal. It was a repackaged VDO as someone mentioned in the e46f thread.

Got it here:

https://www.rockauto.com/en/moreinfo.php?pk=7334076&cc=1432665&pt=10147&jsn=873

Haven't had a chance to replace it yet but it's on the to do list, waiting until the fuel tank is emptier.

My car was also recently SMG to manual swapped, not sure if it is related? The stalling never happened when I was SMG. I'm also considering a VANOS rebuild with Beisan parts.

On a side note, when the fuel pump went out on my e39 530i, never got any codes. The car was difficult to start, very similar to a dying battery, but my battery was still relatively new and put on a battery tender overnight. Would start normally on the second attempt. Confirmed it was the fuel pump when the car died in the middle of an intersection. Had 240,xxx miles on the original fuel filter and pump. Mostly likely the fuel filter clogged with so many miles on it and killed the fuel pump. Couldn't blow any air through the old fuel filter when I pulled it off. Shame on me for not replacing them sooner on the e39, trying to avoid that on the M3. Also replaced the e39 fuel pump with a full gas tank, definitely not recommended.

[Leafsrule531]

I was having similar symptoms as you, car stalling as it was coming to a stop with the clutch pressed down. Since I'm at 137,xxx, I replaced both intake and exhaust camshaft position sensors, the two engine side throttle position sensors, cleaned the ITBs and ICV, and replaced the fuel filter. Still experiencing an idle drop/stumble when coming to stop with the clutch down but not to the point of stalling out. Also considered my fuel pump was dying so I got the Delphi FG1659 from RockAuto for $350 per https://www.e46fanatics.com/threads/...ement.1305176/ which is a steal. It was a repackaged VDO as someone mentioned in the e46f thread.

Got it here:

https://www.rockauto.com/en/moreinfo.php?pk=7334076&cc=1432665&pt=10147&jsn=873

Haven't had a chance to replace it yet but it's on the to do list, waiting until the fuel tank is emptier.

My car was also recently SMG to manual swapped, not sure if it is related? The stalling never happened when I was SMG. I'm also considering a VANOS rebuild with Beisan parts.

On a side note, when the fuel pump went out on my e39 530i, never got any codes. The car was difficult to start, very similar to a dying battery, but my battery was still relatively new and put on a battery tender overnight. Would start normally on the second attempt. Confirmed it was the fuel pump when the car died in the middle of an intersection. Had 240,xxx miles on the original fuel filter and pump. Mostly likely the fuel filter clogged with so many miles on it and killed the fuel pump. Couldn't blow any air through the old fuel filter when I pulled it off. Shame on me for not replacing them sooner on the e39, trying to avoid that on the M3. Also replaced the e39 fuel pump with a full gas tank, definitely not recommended.

Thanks for the insight! I have a feeling it is very likely the fuel pump since my symptoms are similar to your e39 and your e46 but you haven't replaced the fuel pump on your e46 yet which hopefully resolves your issue.

I am actually dreading replacing the fuel pump because I just filled it with a full tank of gas 😭

[Leafsrule531]

Can't help with the diagnosing part but there's the Radium fuel pump "adapter" that fits aftermarket fuel pumps in the space of the factory one. http://www.radiumauto.com/Fuel-Pump-...BMW-P2087.aspx

Could this be a solution for failing pumps as well ?

[PSUEng]

Interesting, thanks OP for posting. I'm at 82kish and had similar starting issues, but replaced my charcoal canister and that seems to have alleviated it. Good to know the stock pumps seem to last a long time, I bought one from FCP in November on sale, and it's on the shelf; crazy how prices have gone to $500 on these. Please keep us updated if the FP resolves your issue!

[sapote]

My guess is my fuel pump went bad but are there any codes that come up when the fuel pump is bad ? I will go home and run the codes and post them here.

Yes, there is sort of 'code' for old weak pump. With the gauge shows about 3/4 to half tank, use the hidden display to show the fuel volume in the left and right tanks: if the left is more than the right then the pump is weak and should be replaced. Normal pump should siphon the left tank into the right and so right is more than left.

Yes, the DME should read and compare the 2 tanks volume, then issues the bad pump error code.

[jet_dogg]

Failing pump won't throw codes.

Also I believe I've seen something on here about smg to manual cars having this because of some issue that escapes me, possibly relay related or some such.

[Leafsrule531]

Okay so I was able to diagnose this further: essentially what is happening is the RPM to drop to 500 or even to 475 when I come to a stop at lights of intersection and then car turns off. Moreover, when I am driving and hit the brake and turn 90 degrees to stop, the rpm drops to below 500 and feels the car about to stall and eventually does.

I also realized that I changed the fuel pump about 20k miles ago so the likely hood of it going bad is low (but still
Possible). Any other thoughts of what could be the issue ?

I've been reading something about cleaning your ICV but have no idea. Also read somewhere about vanos potentially causing this ? Is that true ?

[Leafsrule531]

Also just to clarify, it's not an smg swapped manual. It's a true manual trans.

[undyroos]

How many miles are on the car?

Cleaning the ICV wouldn't hurt. I removed mine to clean but it was already very easy to shake, some oil residue inside but not a lot. Since you have to remove the plenum to access the ICV, might as well clean the throttle bodies as well and change both throttle position sensors while you're in there. I was reluctant to remove the plenum due to the clamps but it is super easy with this tool:

https://www.amazon.com/Lisle-30500-B...0002SREB8?th=1

Super easy to use if you can gain access to the clamps. Pro-tip: my last clamp, closest to the firewall, is installed in the opposite orientation as the first 5 so I have better access to the nubs for clamping and future unclamping. You will see what I am talking about when you take it apart. It is possible to reinstall the clamps such that it is impossible for (future) you to remove them without destroying them so I had to keep reminding myself. There is a happy medium where you can reinstall (fairly easily) and still be able to easily remove them again in the future. I had to pop off the air rail to gain additional access to the last clamp.

Buildjournal has a good writeup on this procedure:
https://thebuildjournal.com/diy-inst...to-rough-idle/

I used this https://www.amazon.com/CRC-05078-Thr.../dp/B000M8PYO2 to clean the ICV and ITBs. If you decide to replace the TPS screws, go with 25mm long screws to match the original screw length. The 20mm screws have very little thread left to engage.

Drove the car a bunch after cleaning the ICV and ITBs and replacing the TPSs and the idle drop has diminished, no stalls so far. I did read that having the a/c on can exacerbate the problem so I need to investigate that as well.

From e46f, VANOS can affect idle:
https://www.e46fanatics.com/threads/...start.1181697/

Slowly amassing my parts from Beisan for a VANOS overhaul.

Good luck!

[Slideways]

Okay so I was able to diagnose this further: essentially what is happening is the RPM to drop to 500 or even to 475 when I come to a stop at lights of intersection and then car turns off. Moreover, when I am driving and hit the brake and turn 90 degrees to stop, the rpm drops to below 500 and feels the car about to stall and eventually does.

I also realized that I changed the fuel pump about 20k miles ago so the likely hood of it going bad is low (but still
Possible). Any other thoughts of what could be the issue ?

I've been reading something about cleaning your ICV but have no idea. Also read somewhere about vanos potentially causing this ? Is that true ?

How full is the fuel tank when this happens? If it is under a quarter tank, the siphon jet tube that delivers fuel from the driver's side to the passenger's side of the fuel tank could be disconnected. The fuel would be stuck on the driver's side and the fuel pump is on the passenger side.

https://nam3forum.com/forums/forum/m...ausing-misfire

A vacuum leak in and around the intake plenum, especially one of the hoses that connects to the brake booster or ICV, will also cause RPM drop and stalling when coming to a stop. Easiest way to diagnose is to test with a smoke machine.

[nahvkolaj]

I am having an issue similar to this but no hard starting. Engine idle will dip below 500 rpm coming to a stop and while sitting at traffic lights. Sometimes dips enough to stall. SMG car.

Recent work done includes full Beisan VANOS rebuild, cleaned ITBs, cleaned ICV, checked idle circuit for bad hoses, replaced all o-rings for plenum connections. I did not replace either TPS while the plenum was off. I did not replace any cam shaft position sensors either.

Thinking about getting or making a smoke tester since this issue has been driving me nuts for almost two years!

[Leafsrule531]

Reviving this again since it's still an issue unfortunately- Here is a video of what ends up happening to the car. It only happens once the car warms ups - in cold idle it never turns off. I just replaced the spark plugs and all the coil packs as well which I was going to do as preventative maintenance anyways.

https://youtu.be/AVzjRNd4fD0

I'll be running the codes tonight using BMW SCANNER. Haven't had a chance to clean the ICV yet.

[nextlvel]

Jumping in this thread to state I am having the exact same issue. I am manual swapped as well