[Ali_____]

So I bought a e92 in September it was a no crank no start type deal, I took a full on risk for a good price. car has 105k on the dash, sat for over a year and wasn't maintained or started. It was a younger kid that owned it and he thought the DME was bad because it had such a bad aliment the steering angle sensor was showing codes and the battery died, long story short the DME was fine but it has a list of other issues. So to my knowledge the car was taken car of the first years of its life then it got passed down to the second owner, it seems like he missed some oil changes and had some shotty work done. The third owner, the kid I bought it from barely drove it and didn't fix anything, it kind of just died and he didn't care anymore. So when I got it I went straight to work after fixing a list of things around the car and fixing shotty work I found myself plagued with this rough idle issue, so I've changed spark plugs, ignition coils, the valvetronic motor seal (vacuum leaking like crazy), intake filter, big disa flap (broke off into the intake), both vanos solenoids, cleaned the vanos solenoid check valves, yet still the car rough idled.

As I drove the car more the problems started showing more. I started noticing only on cold starts it will take a few extra cranks to start, noticed thin white smoke coming out of the tail pipe constantly only at idle. It was never thick like coolant but it smelled like gas, noticed a burning smell coming from the engine (only occasionally) and sometimes I think id get whiffs of gas (don't know if its in the engine or tailpipe), I also get bad gas miles (12 city maybe 15 highway) and a rough idle. But this rough idle only shows if I blip the throttle to 8-900 rpm then let off, it'll drop to 400 sometimes 300 rpm it feels its gonna stall, engine always feels like it has slight misfires, sometimes when the cars hot and I start it I will get misfire codes once cleared they go away completely, it also runs lean but doesn't show codes.

Everything that I found which isn't much on N51, points to either leaky fuel injector or bad O2 sensor. So after some driving for a while I scanned the O2 sensors and they all work fine, 1 of them seemed a lil lazy so I decided to pull it and I found it to be covered in white, then I pulled my spark plugs that I just replaced about 1-2k ago and there also covered in white and I smelled gas. So now I figure leaky fuel injector so I pulled them and tested them, I unplugged the electrical connections but left the fuel lines and injectors connected. I had someone crank the car and I didn't see a single injector leaking, not even a drip. I also connected them and ran inpa to test them and they all click good and shot fuel out normal. So now I'm thinking they could possible have some gunk in them so I pulled them all out and hooked them up to fuel injection cleaner and to a 9v battery. I ran them while I sprayed the cleaner and some gunk did come out but all 6 seem to be shooting nice and strong with the same spray patterns. When I didn't have it hooked up to the battery non of them leaked cleaner and if I built pressure with the cleaner the injector would pop off indicating that its holding pressure.

hooked everything back up even cleaned the o2 sensor up, Put new plugs in the car and still I'm getting the same symptoms. I even see now that the o2 sensor isn't lazy anymore so I don't understand what's going on? now I'm starting to think its something with the fuel pump or tank, I haven't tested the pressure in the fuel rail yet but would a fuel pump make my car smoke white and have a gas smell in the engine like a leaky injector? There's not much info on n51 pumps, all I know is the pressure regulator is built into the tank and that n51s are prone to hose disconnects inside the tank. I've seen some people have fuel pump failure on n51 but all they say is the car just stalled out while driving and they have lugged performance, but no symptoms like me I don't understand.

The car actually drives very good I even took it on a 2 hour drive and back, during that drive I felt like the car really was moving better then ever. I've never felt the car really lose performance, when I drive all it does is rough idle and smoke slightly at stops. The rough idle is mostly present when I deliberately blip the rpm to 8-900. if I go anymore like 1k to redline it wont rough idle at all once back down to 600 rpm.

idk I'm at a loss rn, never had any of these issues with m54 or n52 engines this is the lowest milage car I've ever owned and its newer then my cars in the past. I don't understand is this premature signs of fuel pump failure or something going on in the tank? I think the car has only stalled on me 2 times in the morning but started right up after (I also had a bad vacuum leak when that happened), My fuel gage is also normal I've heard about some not reading lower then half a tank but mines fine, I also don't get any engine codes, and it doesn't even tell me that the cars running lean. Someone please give me some inside on this I feel like I'm going crazy trying to find this out, I drove myself crazy over vacuum leaks at first but now I think this is really a fuel issue. There's some stuff I will try but these symptoms don't make any sense to me.






Pretty much said above, tried most common issues including O2 sensor and injectors but haven't tested fuel pump yet. Getting bad gas miles, few cranks to turn over only on cold starts, fuel smells around the engine, tail pipe (including fuel smoke), and spark plugs, getting white dust on O2 sensors and spark plugs, getting rough idle that only happens on a 8-900 rpm blip, any rev higher and it doesn't rough idle, sometimes a rare stall on cold and a misfire (only misfires very rarely when its hot after its cleared it goes away completely), only on idle either hot or cold feels like the engine is slightly misfiring but nothing crazy. car runs pretty good when driving, no lugged performance and I get no engine codes.






update ********

So today I got around to fuel pressure testing the car, I found that when I prime the fuel pump by unlocking the car the psi shoots to 50 and immediately starts to drop. Within 5 mins it goes from 50 to 34, then within 10 mins it goes to 26 psi. Now when I start the car from cold, during its 3 extra cranks the psi jumps from 0 to 30 in 1 crank, 40 in 2 cranks, then finally starts around 50 psi at 3 cranks, then it goes to 61 psi and sits on idle like that. when I hold 2k rpm it may move to 64 but mostly sits around 61-62 psi, same thing when I blip the throttle to 3k. But now when I blip the throttle to 8-900 rpm to get my rough idle the psi will shoot down around 54, while the rpm shot down to 3-400, then it will jump back to 61 when the rpms normal at 600. Now to the interesting part, when I turn the car off from 61 psi it will slowly go to 74 psi within a 4-5 min span, then sit like that for a few mins until it starts to drop. So 10 mins from 74 it will go to 71, 20 mins it will drop to 55, then after 1 hour it goes all the way down to 5 psi. after 1 hour from last start and at 5 psi it takes a few extra seconds to crank again just like on a cold start. But when the cars hot, maybe 30 mins after the last start, fuel pressure is still there and it will crank usually on the first go.

Does this seem like simply fuel pump failure with no codes, odd symptoms and no pump noises? I've seen on other n51s with bad fuel pressure regulators, usually the psi is in the 40s and drops quickly after shut down. why would my pressure go up to the recommended 70's psi before dropping a little while after if it was the pressure regulator?



update 2 ********

So I got around to pulling the fuel pump and I found some interesting stuff. hoses inside the tank look to be attached and normal (will double check this again). but upon further inspection I found a brown broken plug I think its a broken ground connection, and the black negative wire for the main power supply of the pump is also completely cut apart. the condition of the main negative connection to the fuel pump looks to be sheered or melted off, but at the same time it also looks like someone ripped it apart. from the main power connection housing on the fuel pump housing lid, the copper inside the black wire is exposed and separated going down to where the connection on the pump should be inside the tank, and then on the pump there's burn marks. there seems to be some kind of brown plug in the tank, this looks like it connects to the same negative connection and looks like a ground. it also runs inside the tank that part seems fine, but the part that's supposed to be connected to the negative on the power supply for the pump is sheered off. I also found other stuff like a shit ton of debris on the bottom of the tank, green rubber O ring looks chewed apart, and the 7mm tightening bolt on the clamp was also completely broken and missing, I had to bend the clamp and break it off in order to get the locking seal out.

I think its safe to say someone reckless tampered with this in the past because I've never heard of anything like this happening before. there's a good chance that this is my issue all along, my best guess is that the pump isn't closing right from these bad power connections, causing the fuel to go back into the tank. makes sense why I don't get any codes for it either, usually people do get mixture codes when hoses break inside the tank. pressure regulator still could be on the table, but maybe when the cars off the regulator tries to compensate for the pump, this could be why my psi slowly goes from 61 to 74 in a 5 min span, meaning it still could be trying to do its job. I still don't completely understand the running lean and fuel burn off/smells from the spark plugs, maybe the pump is allowing too much fuel to pass through idk? but this is crazy to me especially those burn marks, I know fuel is non conductive but what was causing those wires to get so hot on the pump? I mean one spark and anyone driving this car could've blown up right? I mean thank god nothing happened to me or anyone else, but I'm kind of surprised nothing did happen since it already got so hot once before. some crazy ass shit this is why some people just shouldn't touch cars, this isn't the first time I've cleaned up shotty work on the car but it was mostly stupid shit that was easy to fix. I'm gonna order the new fuel pump soon, I will update once I install it and hopefully my issue is fixed, I will also post pictures of the old pump soon to show the craziness.