m52b28 stumbling start

[RobinME28]

Hi guys,

A year ago I swapped my m20b20 from my E28 with a m52b28 (from an e39). So far so good. I replaced a lot of things, and the engine was running superb for a while. Last spring I replaced the crankshaft and camshaft pulse sensors as it wouldn't start after 3 months of winter break. Oh and I also replaced the fuel pump with a 4 bar Johns KSP5014002.

The engine was running superb and pulling like all hell broke loose. Though, about a month ago the engine seemed to stall during exiting a roundabout but it didn't. Twice within 10 seconds the RPM dropped to idle and then back to normal with my foot steady on the accelerator (doing 3k RPM at that time). Like there was a fuel cut. Right after that the engine felt less powerful throughout the entire RPM range. Through the day the power seemed to get back to let's say 99% and it still pulls to the red line without any hesitation. But from this moment on the engine seemed to start very weird, stumbling... I can't find out what's the problem.


(don't mind all the lights on the dash, still trying to figure out why they're on)

Trying to solve the problem I've replaced all 6 ignition packs and all 6 spark plugs. Still the engine would not fire up like it did before the "fuel cut" thing happened. Oh and on idle (600 RPM) the engine seem to run on 5 cylinders but when hitting 100 RPM more it would run on all 6... Like WTF is going on here...

Anyone got some advice for me?

[ColtonBH]

Have you checked all vacuum lines?

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[RobinME28]

Yes, I've checked them so often they were almost shouting at me "We're OK!!"

[edjack]

I couldn't detect your symptom from the video.

How many miles on the VANOS seals?

[RobinME28]

Play the video with your speakers on, you will hear

Engine has done 180k kilometers, that's 111k ish miles. Could failing Vanos seals cause the "fuel cut" moment which results in a bad start?

BTW, sometimes the car will start exactly the same as shown in this topic: https://www.bimmerforums.com/forum/s...ith-video-quot

[ColtonBH]

Do m52s have the valve on the fuel rail to test pressure? You should be reading about 45 at rail (3 bar?) At idle. How does the flow on the replacement compare to the OEM, if it is lower, that might explain it, normal pressure at idle but drops too low during high demand. The computer throws a lean code, backs off the timing, and possibly cuts fuel/spark?

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[DHoang]

ColtonBH says, first thing to check is fuel pressure. Are you getting proper psi at startup?
If not, then:

Next, check for fuel leaks at connections.

Next, fuel filter. could be clogged

next, fuel pressure regulator- could be faulty, and diverting fuel supply back to the tank instead of to the engine.

next, what condition is the injector(s)? May have to do a back flush if suspect.