M50 owners:Check your air intake elbows for cracks

[632 Regal]

Also including the M60 with plastic elbows

[Rob Edwards]

Haven't posted regularly in a long time, as my Touring has been pretty reliable. But I noticed a decrease in fuel economy (from ~20 round town to about 17-18), general sluggishness and some pinging on California's 91 octane pseudopremium (I have a D'Sylva chip). I was changing a bunch of coolant hoses last weekend as PM (including that 4-way deal than runs between the expansion tank/thermostat housing/throttle body/heater core- what a PITA) and I noticed that the big black rubber intake elbow itself was split around the connections to both vacuum hoses. The hose from the ICV was also split. So I ordered up a new elbow and ICV hose from BMA and put them in last night. Getting the new hose onto the ICV under the intake was a pain, I ended up having to disconnecting the throttle cables and then moving the throttle body out of the way so I could get my hands in there. I also removed the foreward brace that runs from the lower part of the block to the underside of the intake plenum.

Long story short, the car runs significantly smoother, and feels a lot more responsive. The elbow (13 54 1 726 634) was $28 and the ICV hose (13 41 1 738 187) was $13.

Anyway, this is well worth a check to make sure you don't have an unmetered air leak.

[rizal]

Haven't posted regularly in a long time, as my Touring has been pretty reliable. But I noticed a decrease in fuel economy (from ~20 round town to about 17-18), general sluggishness and some pinging on California's 91 octane pseudopremium (I have a D'Sylva chip). I was changing a bunch of coolant hoses last weekend as PM (including that 4-way deal than runs between the expansion tank/thermostat housing/throttle body/heater core- what a PITA) and I noticed that the big black rubber intake elbow itself was split around the connections to both vacuum hoses. The hose from the ICV was also split. So I ordered up a new elbow and ICV hose from BMA and put them in last night. Getting the new hose onto the ICV under the intake was a pain, I ended up having to disconnecting the throttle cables and then moving the throttle body out of the way so I could get my hands in there. I also removed the foreward brace that runs from the lower part of the block to the underside of the intake plenum.

Long story short, the car runs significantly smoother, and feels a lot more responsive. The elbow (13 54 1 726 634) was $28 and the ICV hose (13 41 1 738 187) was $13.

Anyway, this is well worth a check to make sure you don't have an unmetered air leak.

Is your pinging gone? I tried the EAT chip in my '94 5252iT for a while, on CA 91 octane, and still had pinging under light throttle, so I reverted to the stock chip. Then my mechanic found the same air leaks you describe, replaced the same parts plus a couple small hoses with air leaks and mine too runs much smoother and more crisply, with around town mileage of 20-21 mpg, but I've not put the EAT chip back in yet. Thanks for sharing your experience.

[525iZA]

OK, I'll need some pics of said elbows before I'll be able to check them.

My mechanical knowledge is shocking! :D

[Sixdown]

This also applies to other engines like the M30. The M30 commonly has idle problems and a cracked hose only exacerbates it, especially around the ICV, but luckily mine was replaced before I bought my 535i.

[Rob Edwards]

Is your pinging gone?

Yep, pinging is gone, though I haven't really gone out and flogged it to make everything nice and hot. It wasn't bad before, but it got noticeably worse in the last 5,000 miles or so. I shoulda checked into things sooner but my 928 takes up 110% of my wrenching time!