M30 running on 3 Cylinders !!! help

[genphreak]

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.

Is an M5 alternator the same item? I was only guessing that the 540i one would swap in. Perhaps an e39 or e38 one even, the newer the model the better the alternator. Knowing your ability to access parts these might be good options bud! Have a good weekend, let us all know what happens Nick

[grave77]

I installed my dads E32 alternator ... it was exactly the same on mine. I suppose that u can use the 540 alternators .. I just need to double check in the scrap and compare.

[grave77]

well .. I replaced the Alternator, dist. and rotor. and new HT wires. I still have the same problem.
I tired to investigate a bit further, what's going on is that the alternator is not getting the field power until the engine is reved over 2k, seems that the enigne is running in 3 cyliners when this current reaches the alternator to start charging. I started the engine again and didnt rev it as to keep it running normal. I connected the field bolt to 12V source and the engine started running in 3 cylinders again.

I seem to have a deep electrical problem, therefore I would start were that alternator should get the field current, it should be a relay somewhere. but what is signaling the DME to stop the cylinders. !!

[Bill R.]

fuel to some injectors possibly the cylinders that aren't working for you. Does the eat chip that you have have the rev limiter still in it? If so your voltage problem could be causing trouble with the eat chip and that may be the limiter kicking in at 2k... If you still have the original chip you might try that. But this is all dependent on your being a fuel problem rather than a spark problem. If you have some kind of a huge current draw that too could cause a missing problem but i think it would be random rather than 3 cylinders in a row on the firing order. If your driving a car that has a bad alternator and your driving on battery only as it gets weaker the first things that happen are that the abs light and the airbag lights come on when voltage drops below a certain level and then the engine starts running poorly just before it quits when the battery is too low. The injectors draw a fairly large amount of current, so they are one of the first things affected when battery voltage gets low..

well .. I replaced the Alternator, dist. and rotor. and new HT wires. I still have the same problem.
I tired to investigate a bit further, what's going on is that the alternator is not getting the field power until the engine is reved over 2k, seems that the enigne is running in 3 cyliners when this current reaches the alternator to start charging. I started the engine again and didnt rev it as to keep it running normal. I connected the field bolt to 12V source and the engine started running in 3 cylinders again.

I seem to have a deep electrical problem, therefore I would start were that alternator should get the field current, it should be a relay somewhere. but what is signaling the DME to stop the cylinders. !!

[grave77]

well ... today after I installed the alternator, the car wouldn't start as the battery was low, I jump started it from another car, and when I disconnected the cables it ran poorly just like you mentioned when I reved the engine with the cables still connected to the other car it went into 3 cylinders.

I'm sure it't not a voltage drop but I would guess that there is a signal or something messing up the DME.

one thing I was thinking about, does the Transmission error trigger something like that? as you know I changed the transmisson to manual and didn't short the pins that make it shut up ! ..

but it's been running like that for a long time and I also know that this error makes the auto run the 3rd speed only. so it shouldn't go to the engine.

one other thing I remember was that when I did the last oil change, the OBC wasn't resetting, I don't know if this has to do anything with it too.

[Scott H]

did you gap it properly? has it moved on you? have you tested the coil resistance and voltage values?

the new alternator has a new voltage regulator in it?

just trying to thing of other things to check

[Rustam]

well ... today after I installed the alternator, the car wouldn't start as the battery was low, I jump started it from another car, and when I disconnected the cables it ran poorly just like you mentioned when I reved the engine with the cables still connected to the other car it went into 3 cylinders.

I'm sure it't not a voltage drop but I would guess that there is a signal or something messing up the DME.

one thing I was thinking about, does the Transmission error trigger something like that? as you know I changed the transmisson to manual and didn't short the pins that make it shut up ! ..

but it's been running like that for a long time and I also know that this error makes the auto run the 3rd speed only. so it shouldn't go to the engine.

one other thing I remember was that when I did the last oil change, the OBC wasn't resetting, I don't know if this has to do anything with it too.

Have you used a multimeter to check connection of injectors 2, 4 and 6 with ECU connector? They are connected together as do 1,5 and 3, yet all have common connection on other end with purge valve and relays.

[grave77]

I didn't check the crank sensor ... but I remember that it only takes one position right?
I didn't reach to the injectors yet as I need to remove the AFM and its hoses too. and it was a bit dark today so I was going to do so tomorrow.

what resistance should the multimeter read on an injector?

[grave77]

since the car starts ok ... then messes up after reving it I don't think it's a connection problem, right?

[Rustam]

I didn't check the crank sensor ... but I remember that it only takes one position right?
I didn't reach to the injectors yet as I need to remove the AFM and its hoses too. and it was a bit dark today so I was going to do so tomorrow.

what resistance should the multimeter read on an injector?

Resistance of the injector maybe between 10 and 20 Ohm. Checking injectors for their resistance is unnecessary as we don't suspect them to be faulty since they do inject before 2000RPM. But you want to check the wires connecting to the injectors...

The multimeter reads ZERO resistance when its connected to good wire, showing that there is presence of connection between multimeter leads. Mind that it has to be zero - not infinity. Check for presence of this resistance from every one of those injectors to the ECU while moving neighboring wires 2,4,6 - pin 17 of the ECU 1,3,5 - pin 16 of the ECU...

I would check every one of available connections to ECU in this fashion to make sure that there are no short circuits at all. Have you got wiring schematics?

Since the car starts and revs up to 2000 RPM the problem may be a connection to something that starts acting differently at 2000 RPM!

Fool-proof procedure for finding what's wrong would be to tabulate currnets along all connections to ECU while the engine is running below 2000 RPM and then tabulate all those currents while the engine is running above 2000 RPM. Then see what has changed. Time consuming - yes, but fool-proof.

The problem is obviously electrical and connections are at stake. If all the connections are ok suspect the ECU. If you are ready to open it and start checking it for problems you may want to take a look into this link:

http://frwilk.com/944dme/

He provides electrical schematics for Bosch Motronic 1.3


Set your head at ease by checking all the connections to ECU for short circuits before and after the car has run on 3 cylinders... If they are all well - you've eliminated one possibility - less room for going ...