complete loss of power at high rpms
My 540/6 has had this problem for awhile now. A higher rpms, 5000-6500, there is complete loss of power as if the engine is starved of fuel - it cuts off immediately. This occurs regardless of engine load.
Idle is acceptable with no discernible misses.
Issues that may be remarkable: There is unusually high amount of water vapor in exhaust once the engine is warmed up - more than my 540ia.
There is rather severe oil leakage at both valve cover gaskets and they need to be replaced.
I have done the following:
Thoroughly tested for vacuum leaks.
No oil/coolant in expansion tank/oil sump.
Tested fuel pump/pressure/regulator/fuel filter.
Spark plugs are new and old ones had consistent wear among cylinders.
All injectors functioning and flow is acceptable.
CPS confirmed working.
MAF sensor confirmed working.
Any ideas?
Last edited by jofusfarr; 01-05-2010 at 07:39 PM.
Major Contributor
I think you need not look much further than your valve cover gaskets. These play a pretty damned important role, especially at the higher revs you refer to. So you're loosing essential air pressure and probably leaking fuel intake; there is so much air pressure in an engine that in fact the air gets thrown out the leaks you found and unbalance your engine enough for it to die out.
I thought there was a vacuum in the crankcase, which would manifest problems more severely at idle during higher vacuum?
Grand Master
Change your VCG's and get new coil boots.
High RPM issues are usually ignition related. Coil boots would cause that if they were in need of replacing.
High amount of white exhaust is also a symptom of bad coil boots. Bad boots cause poor combustion which sends raw gas out the exhaust. Raw gas hits the hot cats and burns causing excessive white smoke.
Not only is such a situation bad for your fuel economy, but it'll also kill your cats. Throw new coil boots in there before you need to replace cats, 'cause cats aren't cheap...
Cosmos Black/Black 1995 540iA M-Sport
BMW Individual Exclusive Edition, 1 of 65 total, 9/25/95 Build
Super Moderator
are you sure you're not hitting the factory rev limiter?
Originally Posted by jofusfarr
Fairly sure since it ranges from 5-6.5k. I didn't know the six speed had a rev limiter.
I have taken my 540ia to 7k redline, I expect my 540/6 to do the same.
I just checked coils/boots on the other car and they check out fine at high rpm.
I forgot to mention that when the engine bogs down, the check engine light comes on briefly. The stomp test reveals no codes.
Last edited by jofusfarr; 01-06-2010 at 12:42 AM.
had a similar probem and my fuel filter was the cause
Big Time Poster
+1
I had the same issue many times and it turned out to be either the fuel filters or bad fuel pump.
Major Contributor
The rev limiter does not provoke such issues anyhow. What happens with my M50 is that the engine loses a bit of power and the engine stutters a bit and won't rev higher than 7000. It's possible your 540 has another chip that does not limit it.
But all the same, if your engine is not capped, you would loose power somewhere above 7000 rpms, not the 5-6500 you report. The power peak of the M60B40 is at 5800 rpms, so 6500 would still yield significant power output.
It's always difficult to pinpoint exactly what's wrong with the engine on a forum.
4 Grand Master
I can't speak to the water vapor issue as I don't know where you are. Here in cold Chicago cars that do a lot of short trips are boiling off condensation in the exhaust and it's no worry.
If power tails off at high revs look for a fuel delivery problem, if it sputters or misfires look to the ignition.
"The gas pedal wouldn't go to the floor if it weren't meant to be there"
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