What is this?

[Adam230K]

Got an issue with a car i'm using at the moment;

Its a 2006 545i, and to be honest this issue isn't affecting my drive as such, but I want to make sure it cant evolve into something big because I want to return it in the same shape I got it;

Basically I've noticed that the car will hunt on idle, whether its in D or N it just seems 'unsettled' and you can see the needle moving very slightly and the revs will momentarily drop then you'll get a reactive 'bounce' up again upto to where it should be sitting at 500ish rpm.

Also when I turn the steering wheel the revs change and it sounds like it drops suddenly, then it picks up again. This is also accompanied by a hissing sound as I turn the steering wheel, regardless which way.

My limited mech knowledge is telling me there's an air leak somewhere, how right am i?

 

[momomo]

Have you checked the belts and power steering pump? Is the power steering fluid level also ok?

 

[jaymanek]

id agree, there is an air leak or air metering issue.

 

[Adam230K]

Would this also cause me to 'feel' the gear changes more? They are NEVER harsh by any means, but when it changes gear, especially if I accelerate harder I can definitely feel them. When I first got the car though, I couldn't feel them at all.

 

[jaymanek]

Id guess at mass air flow meter or a split pipe and yes it wil affect gear changes slightly if anything like a mercedes.

 

[Adam230K]

Think I should do the carb cleaner scan before the MAF. I could disconnect the MAF and see if it makes a diff I guess.... I'll let you know what happens later

I love the detective work part of a mechanic's job to be honest

 

[Adam230K]

But the 'hissing' I get from the steering wheel would tell me that its a air leak rather than a simple MAF fault? oooohhh the fun!

 

[Bellow]

But the 'hissing' I get from the steering wheel

Isn't that just the hydraulics of the PAS system?

 

[Adam230K]

Well, this evolved into the loss of power and erratic idling (fine across the rev-range though). I did some tests and found absolutely nothing.

I then pulled up in it outside the dealers and.... Opened the bonnet and disconnected the MAF, the rough idling completely disappeared...!

Problem solved!

 

[Adam230K]

Ok I've got something else now which (just for knowledge sake) i'd like to know what it could be.

When I rev the engine, it will rev freely, but as soon as I let my foot off the revs, it takes some time to fall back down to idle... especially when it gets to 1k and below, 1k down to idle takes alot longer than it should. Any ideas why?

Car has new MAF now. P.S. I'd also like to say that it did this before I changed the MAF.

 

[Adam230K]

Any Ideas?