intermittent intake air leak ----

[fairchild]

I am getting an intermittent intake air leak. (getting lean codes, fuel trims out of range, sometimes cyl misfires.)
It all seems to be coming back to maybe an intake air leak. I can never feel roughness-- cant tell if there is any power loss on the road--
(cause this is my first BMW)

I tried taking carb cleaner and straying around the rubber intake boot- and arround the little bellowed offchute- and somewhat arround
the hose going to the dipstick and also around the brake booster hose. Did not hear any change in RPM while doing that. Where else do I look
to spray carb cleaner ? Do I need to take the plastic engine top cover off and try to spray the intake manifold gaskets ? (if I can see them...)

Planning on ordering the rubber boots new on monday.

Any hints where to look.

It is running pretty well otherwise..........

Thanks ahead of time for your thoughts .......

Tim

[Mr Bingley]

I've never found carb cleaner to be very effective in tracking down a vacuum leak--I use starting fluid; use it judiciously though, it's very flammable.

[rf900rkw]

Carb or Brake clean do work. But not like the old days where it takes a garbonza air leak to make you notice something is wrong. Teh leak will be small. When combined with the self-correcting maxture and idle speed controls, you will never here an RPM change.

Plug in your scanner routed so you can see it under the hood. Set it so you can easily see both STFT; Short Term Fuel Trims, for bank 1 an bank 2. The trims should be positive, likely upwards of 10. Lightly and fainily spritz each suspected area, watching for the trims to jump way down... maybe into the negatives. Intake boot, manifold gaskets (never seen them fail) and Valve cover gaskets, both outside and down in the plug wells.

[colb]

If your certain there are no air leaks then turn your attention to the Maf, cleaning it with electronic cleaner spray is worth a try but won't do anything if its on its way out. I searched high and low for air leaks eventually changing the Maf for an oem Bosch or Siemens make cured my running problems. Bad Mafs do not always set a code its more likely that sensors further downstream will set codes as the fueling is out due to a bad maf not reporting the airflow correctly.

[rf900rkw]

Oh, forgot. M52TU has three vacuum posts on the back of the manifold, two of them capped. The caps rot and fall off.

[LannVouivre]

Another trick I did was I put a cylindrical container into the intake boot in place of the MAF, put my air compressor onto a vacuum port, and ran very low psi pressure into the intake system while spraying soapy water everywhere. I would loosen the oil fill cap to let off pressure. It's like a smoke machine, but probably not very good to pressurizeq vacuum system like that. I had to improvise when the transistor blew on my power supply again.