BMW 318 E91 2.0 N46 ME9 2007 - Stalls on over run, then no compression #
Posted by Alan Potter on August 29, 2017, 10:58 am
Year of Manufacture *: 2007|
Engine Size and Code *: 2.0 n46
( Optional ) ECU Type: ME9
( Optional ) Scanner Used: dis
( Optional) Fault Codes: none
Starts fine hot or cold idles fine. If given a hard rev it will rev as hard as you want and you can hold it at high revs.
However after a good rev, on the over run it always stalls and when you try to restart there is no compression at all. After a min or two if you try again it sounds like some compression has returned as it try's to start or starts and runs rough. If left for longer it starts perfectly again.
There are no fault codes. However there was a code for the variable valve lift concentric shaft motor out of range. The garage that sent it to me had found a code for a valve lift and replaced the motor.
that had made no difference but after I ran the calibration procedure there are now no codes.
I of course also suspect a valve fault.
I have been looking at the vanos and valvtronic systems. i have ran the tests for both using DIS and you can see the valve lift variation from 0.4mm to 9.0mm also you can advance and retard the vanos on both cams with the tool and see the variation on the screen. So the bm test plan says no faults.
So it is working at idle as it is supposed to.
If I disable by disconnecting lift motor or vanos solenoids the system is then in to limp mode
the lift defaults to 9mm as it should the vanos returns to base setting as it should and now the throttle body takes over and the fault disappears
although it is obviously a bit down on power due to limp mode.
I have remove and cleaned the vanos solenoids
and I have access to another car so I may swap them over as a quick test to discount them.
I am going to try to scope test the concentric shaft position sensor which I understand can suffer from oil ingress. but as there are no fault codes I am also thinking about a possible mechanical fault and have found a post on line showing plastic debris possibly from the chain tensioner that had blocked the oil pressure relief valve. That would possibly jack the valves open and/or effect the vanos. accessing the oil pump it an engine out job. And so not for me (I concentrate on electrics and diagnostics)
the concentric sensor is expensive and takes a bit of time to fit. And given the customer has already had someone spend a few hundred on a guess at the motor, I cant be trying one unless I have strong evidence to suggest it is faulty.
sorry about the long post. So an oil pressure test (id have to borrow a gauge) or more testing of the concentric sensor is where I am at the moment.
If it was high oil pressure jacking the valves the fault would not disappear when the vanos is disabled would it?
But you would thing oil in the concentric would show up on the dis test plan.
I donít ask for advice very often but this one
has my head spinning so any help would be appreciated