Reply With Quotethe crank sensor is new .. I had it screwed up before ... the alternator was faulty but the car was working without a problem before. I'm thinking of a full reset. whould this help?
Major Contributor
Before going any farther with the ECU, you should fix the alternator. You know something's wrong there and depending on the nature of the failure it's possible that it could be screwing up the ECU.
Also check the crank position sensor. They are known problems -- they loosen up, move away from the phonic wheel, and leak oil. It's tricky to get to, check your Bentley for instructions.
Major Contributor
the crank sensor is new .. I had it screwed up before ... the alternator was faulty but the car was working without a problem before. I'm thinking of a full reset. whould this help?
Major Contributor
If the electrical system is having problems, you can't necessarily depend on any systems that depend on it. I've been an electrical/electronics engineer for a LONG time (in aircraft and automotive instrumentation and power systems), and one of the principles that has served me very well over the years in making nonworking things work is this: "Fix what you know is broken." IOW, if you have a system with multiple problems, any of which are of unknown origin, you first fix the problems you know about, with the knowledge that sometimes (but not all the time) the unknown problems are dependent on the known one/s.
To put it another way, it's doubly difficult to troubleshoot a problem when you are dealing with a known problematic associated system. In your case you are having engine management problems. The ECU and related systems heavily depend on a good source of DC power, yet at the same time you know that your alternator is having some kind of problem. Ergo, FIX THE DAMN ALTERNATOR!!! 8-)
It probably wouldn't hurt to pull the connector off the ECU to reset it. I think this is much easier than disconecting the battery because all other systems (radio, trip computer) keep their power. The ECU is easy to reach. It's in a box on the right side of the firewall, right in front of the windshield. The ECU is the module closest to the windshield. The connector comes off by unhooking the bail and pulling it up. Keep it off for a minute, then reconnect and give it a try.
Big, Big Time Poster
With fuel smell, it sound like ignition to me also. Pull and inspect distributor cap & rotor. Cyl's 6, 2 and 4 are sequential in the 1-5-3-6-2-4 firing order. Look for carbon tracks.
Pull a plug from 2,4 or 6 after running engine. Wet plug means ingnition problem, dry plug means fuel problem.
Injectors 2,4,6 are energized simultaneously. Pull off rubber boot from an affected cylinder and backprobe connector with DMM. Other DMM lead goes to engine. With engine running, should measure 12V continuously on one pin. The other will read less then 12V, as DME completes circuit to ground.
Paul Shovestul
Originally Posted by Jeff N.
Last edited by Bellicose Right Winger; 02-21-2006 at 11:11 AM.
.....Got to keep the loonies on the paath.
Major Contributor
i already tried another ECU i have as a spare, didn't help up. i'll fix the alternator and see.
i'll keep u posted ..thanks a lot
Major Contributor
plugs were dry, black as the AFM is not very good. the gas smell was when i disconnected the cylinder identification sensor.
i'll do the DMM check today i'll see the signal with a portable oscillascope (the wire to DME)
thanks mate
4 Grand Master
I know its a sore point, but I know that traditionally alternators die at high rpm. I think in many cases they are closely matched to the speed range of the motor for efficiency reasons. My experience with older Fords proved this many times (all of mine had Bosch (but certainly not BMW spec) alternators)
It'd be interesting to know how they are rated by the manufacturers in this respect, ie- is a 540 alternator the same or is it a bit better at higher rpms? (assuming M60s have higher rev limits than M30s)... it'd help us know what to do if we start increasing the rev range of our motors (for the keener ones amongst us...)
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Super Moderator
As Paul states if your sure that your getting fuel on these
cylinders, ie you checked it with a noid light and saw the injectors were pulsing then it sounds like ignition.. and the fact that its three sequential cylinders on the dist cap also sounds suspicious, i would also pull the dist cap and rotor first and see if somehow the dist cap is off center, perhaps a poorly made one that isn't centered exactly on the dist or if the rotor and cap contacts are extremely worn so that the gap is much greater on one half of the dist rotor to cap as it turns which would cause it to need much more energy to jump the gap under load or at higher rpms.... does it only miss at higher rpms under load as your accelerating or does it continue to miss even when your cruising at one steady speed with the rpms above 2k?
Major Contributor
well ... when the car starts everything is fine ... after I rev it over 2K it starts to vibrate telling me that its running on 3 cylinders. the spark is reaching to the plugs as when I pulled the plug wires I saw the spark jumping to the spark plugs but the engine did not change its behavor only cylinder 1, 3, 5 did change when I pulled the plugs wire. I would say that a bad distributor will make the engine skip one spark or two but not all the time.
when I switch the engine off and on again it returns with all the cylilnders on until I rev it over 2K again to run in 3 cylinders.
Does the ECU detect bad injectors? or my alternator is charging with crappy current that affects the ECU badly?! anyway I got an alternator used to be for my dads E32 ... I will install it tomorrow and see.
Major Contributor
that's something else Nick ... what I need now is to make the engine rev back to acceptable limit mate !! ...
but if I wanna talk about the alternator, M30 alternators are noisy ... actually they are the most noisy alternators I experienced. I felt that when I installed my audio system, so if there are more quiet alternators that would be an upgrade. but I don't recommend more power since it's already 140A ... more current will kill the battery.
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