Ideally, what should be Idal RPM for M50 (92 525i) engine?

[Akhil]

Hey guys,

Can any body tell me what should be Idal RPM for M50 engine (ideally) ? Mine runs on around 600 RPM. Isn't it little low?

[Kalevera]

I consider ~ 800 normal.

best, whit

[Akhil]

Means mine is running low. Can any body tell me what could be probable causes which can bring idal RPM low and what causes raise high?

Thanks

[Akhil]

Can any one else tell me what Idal RPM your engine runs and what it should be?

[Dave M]

91_525im

700 rpm is most common for mine, rarely 800.

I've seen mine idle at 600. Unless there are other issues, I wouldn't worry about it. Oskar would like to know if your idle is ruff.

Dave M

[Mendozart]

Mine used to be about 700 but since I recently reinstalled my EAT chip it is about 600, sometimes almost 500. Idling smooth though.

[Akhil]

I don't think my Idal is rough but since its low even if I cleaned ICV and all its connecting hoses with throttle body cleaner and replaced O-Rings on connectors. I am suspecting that I have vacume leak. I hear some hisssssss......ing noice around intake mainfold while engine running. Does valume leak brings idal RPM Down or UP?

Thanks

Akhil

[Akhil]

One more thing I forgot to tell. I have really bad gas milage:( . 15-16 MPG with AC off and 14-15 MPG with AC on in city. Can vacume leak couse low gas milage?

Thanks
Akhil

[Dave M]

Uhhm, that sounds low to me and, if it is, could be a symptom of a vacuum leak. Been a while since I've driven pure city (thank someone upstairs) so don't take my word on that. Yes, the idle should drop slightly with a vacuum leak. A trick I learned here is to take a piece of plastic bag and seal the oil filler hole with it while the engine is running (leave it a bit loose so it can move up and down). Without a vacume leak, the plastic with be sucked slightly into the hole (vacuum present).
If the bag doesn’t get sucked in at all, and the idle ‘note’ doesn’t change, then update us. Others here will be better able to help you diagnose a leak if we suspect one.

Good luck,

Dave M

[Akhil]

Thanks for all your reply guys,

I am gonna try that and let you guys know the result. But I was thinking to take intake mainfold out and replace intake mainfold to head gasket, throttle body to mainfold gasket and all the hoses and breather tubes under intake mainfold, since its about 13 yrs old car and rubber tubes and hoses go bad with heat and time. What do you guys think about it? How hard this job is? What are the gaskek, seal rings, O-Rings I would need need for this job?

Thanks
Akhilesh