A quick heads up for you guys.
Had a Z4 in my shop a few weeks ago that had the above codes. Fuel trims at idle were indicating lean conditions on both banks, but as it was revved the fuel trims improved. PERFECT symptoms of an air leak.
My next step is to hook up the smoke machine. But as they cost about £1000 not everyone will have one! Anyway, smoke in and guess where the air leak was?....The oil filler cap! Not fully tightened. Simple eh??
BMW engines are very sensitive to the crankcase ventilation. Starting the engine with the oil filler cap removed, for example, will show you why!! Apart from a bit of oil around, the idle will be rough.
Any PCV pipe around the engine need checking thoroughly. the ones under the inlet manifold are prone to splitting.
After the oil filler cap was tightened, i then pulled and pushed the air filter box from left to right to simulate engine rock when accelerating and decelerating. This revealed more smoke coming out of point where the ducting that goes from the air flow meter joins with the inlet. A slightly loose jubilee clip was the culprit. Very hard to miss because the engine torques over under power. A hesitation in acceleration will be a possible symptom.
Pouring water over the pipes, ducting etc is another good way to find an air leak. No, it wont harm the engine!! You will be able to hear it sucking the water in and the engine stumbling possibly.
Hope all this helps a bit.
Had a Z4 in my shop a few weeks ago that had the above codes. Fuel trims at idle were indicating lean conditions on both banks, but as it was revved the fuel trims improved. PERFECT symptoms of an air leak.
My next step is to hook up the smoke machine. But as they cost about £1000 not everyone will have one! Anyway, smoke in and guess where the air leak was?....The oil filler cap! Not fully tightened. Simple eh??
BMW engines are very sensitive to the crankcase ventilation. Starting the engine with the oil filler cap removed, for example, will show you why!! Apart from a bit of oil around, the idle will be rough.
Any PCV pipe around the engine need checking thoroughly. the ones under the inlet manifold are prone to splitting.
After the oil filler cap was tightened, i then pulled and pushed the air filter box from left to right to simulate engine rock when accelerating and decelerating. This revealed more smoke coming out of point where the ducting that goes from the air flow meter joins with the inlet. A slightly loose jubilee clip was the culprit. Very hard to miss because the engine torques over under power. A hesitation in acceleration will be a possible symptom.
Pouring water over the pipes, ducting etc is another good way to find an air leak. No, it wont harm the engine!! You will be able to hear it sucking the water in and the engine stumbling possibly.
Hope all this helps a bit.