[Herby303]

Hi all,

Looking for a bit of advice on a screech and lumpy engine.
E93 325i (2008) N53 105K

I started hearing a slight screech from the engine bay around a month ago, usually after the car had warmed up, or if idling, around 2000RPM. Was told it was the Alt. belt so I had it replaced, problem still the same.


A few days later the engine was running lumpy and was throwing the P0171 & P0174 too lean codes (both banks). Took it to BMW for a proper diagnostic as I only have a cheap one, they said I need to replace all 6 injectors. The squeal doesn't kick in till its warmed up and coming mainly off throttle so BMW might not have heard it.


I'm no expert, a novice in fact, but I was sceptical. I've had no engine light on at any point, no misfires, the car runs fine when driving, just lumpy idle.

I cleaned the MAF sensor, checked air filter and casing, removed the intake boots and checked for rips etc, all seemed fine. I stopped at the throttle body as that's where my knowledge ends. Also added a can of Liqui Moly Injection Cleaner which seems to have helped with the lumpiness (not happening as much) but problem still persists. Got a better scanner arriving soon which checks O2 sensor and air flow so hopefully I can see if they're dodgy.

From what I've read I understand it could be loads of things related to vacuum or O2/MAF sensors etc, and I'm not expecting a quick answer but does anyone think this could be anything other than full injector replacement?

The price BMW quoted me was around half the worth of the car.

Does the fuel pump ever make this noise? I read FP issues can throw up the lean codes.
I'm thinking the horrible sound and the codes aren't connected issues, but would be good to rule it out. Sounds like a pulley/tensioner maybe? Hopefully somebody knows this sound as I don't know how many more YT videos of screeching BMW engines I can handle

Thanks for any help, as I say, I'm a novice. Most of what I know is stuff I've learned in the last month trying to get to the bottom of this.

Horrible Squeal & Lumpy here:
https://www.dropbox.com/s/76ubu5klvd...reech.MOV?dl=0

Cheers

[TunafishE93]

I would take it to get warranty, you should be under the 15/150k emission warranty with the n53 and with those codes should apply. I guessing PVC but don't know the N53 well.

[Herby303]

Never heard of that, from a quick read I’m guessing it’s a US thing? I’m in UK

[TunafishE93]

Yeah US.

[Herby303]

That’s a shame, cheers anyway

[lookalikehuuh]

any chance you could post a video of the noise? I think it would go a long way to helping you diagnose the issue.

[drymite]

Originally Posted by Herby303

Hi all,

Looking for a bit of advice on a screech and lumpy engine.
E93 325i (2008) N53 105K

I started hearing a slight screech from the engine bay around a month ago, usually after the car had warmed up, or if idling, around 2000RPM. Was told it was the Alt. belt so I had it replaced, problem still the same.


A few days later the engine was running lumpy and was throwing the P0171 & P0174 too lean codes (both banks). Took it to BMW for a proper diagnostic as I only have a cheap one, they said I need to replace all 6 injectors. The squeal doesn't kick in till its warmed up and coming mainly off throttle so BMW might not have heard it.


I'm no expert, a novice in fact, but I was sceptical. I've had no engine light on at any point, no misfires, the car runs fine when driving, just lumpy idle.

I cleaned the MAF sensor, checked air filter and casing, removed the intake boots and checked for rips etc, all seemed fine. I stopped at the throttle body as that's where my knowledge ends. Also added a can of Liqui Moly Injection Cleaner which seems to have helped with the lumpiness (not happening as much) but problem still persists. Got a better scanner arriving soon which checks O2 sensor and air flow so hopefully I can see if they're dodgy.

From what I've read I understand it could be loads of things related to vacuum or O2/MAF sensors etc, and I'm not expecting a quick answer but does anyone think this could be anything other than full injector replacement?

The price BMW quoted me was around half the worth of the car.

Does the fuel pump ever make this noise? I read FP issues can throw up the lean codes.
I'm thinking the horrible sound and the codes aren't connected issues, but would be good to rule it out. Sounds like a pulley/tensioner maybe? Hopefully somebody knows this sound as I don't know how many more YT videos of screeching BMW engines I can handle

Thanks for any help, as I say, I'm a novice. Most of what I know is stuff I've learned in the last month trying to get to the bottom of this.

Horrible Squeal & Lumpy here:
https://www.dropbox.com/s/76ubu5klvd...reech.MOV?dl=0

Cheers

Does it sound like thtis?

[Herby303]

Hi, the video is attached at the bottom, do you not see it? I’ll repost if not, cheers

[Herby303]

https://www.dropbox.com/s/76ubu5klvd...reech.MOV?dl=0

Here it is again, let me know if you can see it, thanks

[tcphoto]

I would not throw parts at it, odds are you are only wasting money. Take a flat head screwdriver and from the back of the tensioner apply a little pressure. If the sound stops replace the tensioner, if the pulley is chipped replace it also. The lean codes are from a vacuum leak, unmetered air is entering the system. I'd start by checking vacuum hoses for cracks and boots leading to the throttle body.

[Herby303]

Originally Posted by tcphoto

I would not throw parts at it, odds are you are only wasting money. Take a flat head screwdriver and from the back of the tensioner apply a little pressure. If the sound stops replace the tensioner, if the pulley is chipped replace it also. The lean codes are from a vacuum leak, unmetered air is entering the system. I'd start by checking vacuum hoses for cracks and boots leading to the throttle body.

Cheers, I'll try the tensioner thing next time it happens.

Checked the boots and elbow they look ok, but I'm not really sure what vacuum hoses I should be checking, It's all new to me. How many hoses are there on the N53? I can look it up then, cheers

Can anyone confirm if the video link above is working?

Thanks

[Herby303]

Originally Posted by drymite

Does it sound like thtis?

No, its more of a constant squeal.

Thanks

https://www.dropbox.com/s/76ubu5klvd...reech.MOV?dl=0