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Old 12-31-2012, 05:07 PM
stuartjohn24 stuartjohn24 is offline
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Location: Chippenham, Wiltshire, UK
 
Join Date: May 2011
Posts: 667
Mein Auto: BMW E65 745i
Hi 745i guy,

It was a mixture of things, symptoms when cold were misfiring causing severe vibration for 30 seconds after start if left idling.

During the warmup phase base once hot had many drive ability issues. Lagging in gears, I could be cruising doing 40mph at approx 1300rpm, hit the throttle depressing approx 10mm would result in an immediate dip of approx 150rpm, no acceleration just a loud exhaust noise. Very slow pickup, to accelerate you would need to push the accelerator down another inch or so almost to kickdown.

While cruising and approaching an incline the car would start slowing down and struggling unable to maintain a constant speed.

It was very annoying the DME would not show any errors but it would drive like a pig!

Sometimes, possibly 10% of the time after a cold or sometimes hot start it would drive amazing! Then bog down again.

I done an engine conversion on my old E46, removed the 1.8 4 pot and fitted a 2.5 6 pot, had similar issues, after a hot start it would stall when idling, turned out to be the camshaft sensor not being able to pick up the camshaft once it was hot.

The sensors are Hall effect, when hot and cranking the camshaft was not moving fast enough for the sensor to pick it up! That didn't throw any codes either!

I do wonder if the EU DME software is more ignorant to engine sensor faults than US spec ones.

Problem is the DME uses the cam sensors for the VANOS timing and I'm convinced that after time these sensors become less sensitive and introduce a lag or delay in the camshaft position information for the DME making it think the camshaft is in a position that its actually not. This I believe is causing the very poor performance.

I would recommend changing all 4 sensors! Wish I had the cash to at the moment! Simply cleaning and swapping them around has dramatically improved mine so far!

Stuart

Edit: one other thing, you can get prolonged cranking times when starting or starting then misfiring immediately. This also points to dodgy/intermittent cam sensors. Again when hot it would misfire when starting or crank over a few more times than normal. As you know they usually start immediately.

Last edited by stuartjohn24; 12-31-2012 at 05:14 PM.
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