1993 850ci Running on one bank

[Blaizefed]

Hi All,

We have a customers car in the shop and we are running out of ideas as to what to look for to solve the problem. Car was running fine when it came in and was here for issues unrelated to the engine. However it developed an occasional and now permanent running problem while we had it in. Customer advises its been doing it off and on for a few months. Well its all the time now.

Seems it is running on one bank of cylinders. 1-6 are not working. When the injector plug is pulled on any cyl on the 1-6 bank it has no effect on the (lumpy) idle. The signal on that side when tested with a noid light is very weak. Dim flashes. MUCH brighter on any of the 7-12 cylinders. We also have no motion at all on the cyl 1-6 T-body. Doesn't even twitch.

so far we have swapped form one side to the other the coil, plug wires, cap, rotor, MAF, Throttle body, DME's, DME relays. I swapped the fuel lines at the fuel filters around. none opf thatr changed anything. I have checked continuity between the DME and the injectors on the dead side. Checked all the power and ground terminals at that DME, all ok. CHecked for continuity between the dead T-Body and the EML control unit. all ok there. I have to assume the EML is working as the other throttle body works fine.

Plugs are ok, fuel is fresh, cant find a blown fuse anywhere. The EML light is on and the 2 codes in the system are "201 O2 control" and "16 Ignition system" neither of which tell me much. Spark looks good. Plugs are reasonably new and clean.

I am pulling my hair out here. the one thing that has me scratching my head is that it will not run without both of the crank sensors plugged in. My understanding was that they feed each of the DME's right? so presumably I shoudl be able to unplug the one for cyl 1-6 and see no change right? I have not swapped them as they are pretty involved to move around. But I may try that next.

It does feel an awful lot to me like it is in some sort of limp mode as the injector signal is weak and one throttle body is not moving.

This sound at all familiar to anyone here? Any ideas?

[shogun]

here are the data and locations of the crankshaft position sensors and the cylinder identification sensors on ignition wires 6 and 12, test these first https://www.bimmerforums.com/forum/s...ght=cps+sensor
How do the spark plugs 6 and 12 look, wet, etc? Any sparks? which type of spark plugs?
Check wiring between e-box and throttle valves , broken wires on an M70 in an E32 750, >>> Weird electrical problem - throttle wiring is hinky, sends DK into spasm http://www.bimmerboard.com/forums/posts/644209/

another case solved 750il-dropping-into-6cyl-limp-home-mode https://www.bimmerforums.com/forum/s...&highlight=CPS
850i-M70-M1-7-runs-only-on-bank2-and-even-on-this-one-it-is-rough-No-codes-SOLVED https://www.bimmerforums.com/forum/s...ghlight=shogun

check the throttle valve (DK), test data on my website, DK input details : small PDF file http://twrite.org/shogunnew/data/controlsystems.html
throttle body cleaning , info my website, http://twrite.org/shogunnew/files/DK...h%209_2012.pdf
21 pages detailed DK info, go to my website, >>>fixes>>engine Rebuild the throttle bodies - detailed write up, many photos, http://twrite.org/shogunnew/topmenu.html

[cartoonz]

Sounds to me like the Crank sensor (not the cam sensor) is failing for Bank 1

[CD05001CIA]

Hi All,

We have a customers car in the shop and we are running out of ideas ......
.....

...... ector signal is weak and one throttle body is not moving.

This sound at all familiar to anyone here? Any ideas?

First and foremost, How the 'system' works. There is a sensor on the plug wire on each bank near fire wall that senses spark current.
The nic name is 'donut sensor'. If the DME is not getting a 'yes there is spark current in the plug wire on plug wire #6 / #12 the DME shuts down the injectors so that un-ignited fuel will not collect.

Reasons the DME might not be getting the signal:

The spark plug is wet inside the cylinder and there is no spark.

The plug wire is old and doesn't conduct well or is allowing the charge to leak.

The donut sensor is faulty

The electrical connections between the DME and the donut sensor are corroded.

The coil is expanded(swollen) and is bad or intermittent.

The interior of the rotor cap is soiled and the charge is leaking on the conductive path.

The carbon pin in the rotor cap is worn down or the spring behind the carbon pin is 'kaput'.


You get the idea....

Crank sensors do what their name implies. They let the DME's know that the engine is turning.


You need to clear codes or dis-connect both battery negative terminals to guarantee that the ECU(EML + DME + DME) will try again.

If the DME has 'set a flag' that there is no spark, it will not activate the injectors.


Cartoonz nearly always gets the answer right like 99.5% of the time!

[LappingLuke]

Doesn't EML light pretty much mean the DK on the bad bank is failed and it's not trying to operate that bank?

[CD05001CIA]

Doesn't EML light pretty much mean the DK on the bad bank is failed and it's not trying to operate that bank?

That is as possibility... EML light can be illuminated for other EML issues also. It is possible to put key in position 2 while the rubber boot to the DK is removed and then have one person slowly depress the accelerator while another person watches the 'butterfly', 'brass disc' in the DK move/open and follow the position of the accelerator pedal.

[dragon850]

Doesn't EML light pretty much mean the DK on the bad bank is failed and it's not trying to operate that bank?

Exactly.

- - - Updated - - -

Hi All,

We have a customers car in the shop and we are running out of ideas as to what to look for to solve the problem. Car was running fine when it came in and was here for issues unrelated to the engine. However it developed an occasional and now permanent running problem while we had it in. Customer advises its been doing it off and on for a few months. Well its all the time now.

Seems it is running on one bank of cylinders. 1-6 are not working. When the injector plug is pulled on any cyl on the 1-6 bank it has no effect on the (lumpy) idle. The signal on that side when tested with a noid light is very weak. Dim flashes. MUCH brighter on any of the 7-12 cylinders. We also have no motion at all on the cyl 1-6 T-body. Doesn't even twitch.

so far we have swapped form one side to the other the coil, plug wires, cap, rotor, MAF, Throttle body, DME's, DME relays. I swapped the fuel lines at the fuel filters around. none opf thatr changed anything. I have checked continuity between the DME and the injectors on the dead side. Checked all the power and ground terminals at that DME, all ok. CHecked for continuity between the dead T-Body and the EML control unit. all ok there. I have to assume the EML is working as the other throttle body works fine.

Plugs are ok, fuel is fresh, cant find a blown fuse anywhere. The EML light is on and the 2 codes in the system are "201 O2 control" and "16 Ignition system" neither of which tell me much. Spark looks good. Plugs are reasonably new and clean.

I am pulling my hair out here. the one thing that has me scratching my head is that it will not run without both of the crank sensors plugged in. My understanding was that they feed each of the DME's right? so presumably I shoudl be able to unplug the one for cyl 1-6 and see no change right? I have not swapped them as they are pretty involved to move around. But I may try that next.

It does feel an awful lot to me like it is in some sort of limp mode as the injector signal is weak and one throttle body is not moving.

This sound at all familiar to anyone here? Any ideas?

I would start with a smoking gun, EML light on means one of 2 things, throttles are bad or EML computer is bad.
I can rebuild the throttles since they are more likely to fail and go from there.
Cheers

[LappingLuke]

dragon850 exchanged my bad ones for his rebuilt ones right after I got my car. I highly recommend this very specialized, crucial service for our cars.

[Blaizefed]

Right, thanks for all the input guys. TO answer some of your suggestions, I have swapped from one side to the other, ALL the ignition parts. Coil, wires, cap, rotor (the wires don't fit well of course on the wrong side, but well enough for testing purposes). all with no change. So I have got to assume that all of that, donuts included, is working.

We were then suspect of the crank sensor. Given that they are a bit more of a pain to get too, inexpensive, and damn near 30 years old, I replaced them Friday afternoon. No change.

Dragon850 if you are relatively certain that an EML light points to either the EML computer or a faulty throttle body than that does narrow things down a great deal. We do have the EML light on whenever it is running. One other symptom that we had for a little while was that if we put a charger on the car and let it sit for a while charging and then crank with the charger on, it would run on all 12. No EML light. Turn it off, turn off the charger, start it back up, and back to 6 with the EML light on. (we did load test the batteries and both are well within spec. 13 and change volts sitting still and 11.5 when cranking. They are also less than 2 years old and Interstates). This is no longer the case. Its 6 all the time now. But may support a faulty EML computer, or a bad power or ground connection to it?

I have swapped the throttle bodies around once already so have got to think they are ok. But I very well may swap them again just to make sure. and that would then point to a fault with the EML computer?

While I have checked continuity between both throttle bodies and the EML computer, I do not have in my notes that I have check the power and grounds for that computer. So I'll swap the T-bodies around again, check for good power and ground at the EML computer, and then we will have to ask around and see if anyone we know has a good used EML computer for us to try.

Feel free to throw any more ideas at me. And I will report back with my findings as I go. Thanks again for all the help so far. This is a good forum.

[LappingLuke]

The EML light is only on to tell you something is wrong with the EML so troubleshooting anything before figuring out what the EML fault is just a distraction! Throttle bodies (DK's) are a known failure point. When I got my car I had to drive it 1000 miles home in limp mode because the DKs were bad. It took about 30 mins for the light to finally trip on and enter limp mode but it did not run well even before the light came on. I made it home pretty much entirely on 1 bank of cylinders...

[rjjablo]

Test the Relays in the Computer box on the Passenger side of the engine compartment. 4 relays in there might as well test them all. I had 1 of the fuel pump relays that would quit when I hit a bump and throw the EML Light.

[dragon850]

Right, thanks for all the input guys. TO answer some of your suggestions, I have swapped from one side to the other, ALL the ignition parts. Coil, wires, cap, rotor (the wires don't fit well of course on the wrong side, but well enough for testing purposes). all with no change. So I have got to assume that all of that, donuts included, is working.

We were then suspect of the crank sensor. Given that they are a bit more of a pain to get too, inexpensive, and damn near 30 years old, I replaced them Friday afternoon. No change.

Dragon850 if you are relatively certain that an EML light points to either the EML computer or a faulty throttle body than that does narrow things down a great deal. We do have the EML light on whenever it is running. One other symptom that we had for a little while was that if we put a charger on the car and let it sit for a while charging and then crank with the charger on, it would run on all 12. No EML light. Turn it off, turn off the charger, start it back up, and back to 6 with the EML light on. (we did load test the batteries and both are well within spec. 13 and change volts sitting still and 11.5 when cranking. They are also less than 2 years old and Interstates). This is no longer the case. Its 6 all the time now. But may support a faulty EML computer, or a bad power or ground connection to it?

I have swapped the throttle bodies around once already so have got to think they are ok. But I very well may swap them again just to make sure. and that would then point to a fault with the EML computer?

While I have checked continuity between both throttle bodies and the EML computer, I do not have in my notes that I have check the power and grounds for that computer. So I'll swap the T-bodies around again, check for good power and ground at the EML computer, and then we will have to ask around and see if anyone we know has a good used EML computer for us to try.

Feel free to throw any more ideas at me. And I will report back with my findings as I go. Thanks again for all the help so far. This is a good forum.

I am like 99% sure your problem is throttles of EML computer, sometimes swapping throttles does nothing because both of them could be causing EML light but still allowing the car to run.
Need to start with throttles and then move on to EML.
PM me if you decide to have them rebuilt, then move on to EML computers which I also have pre programmed.

[CD05001CIA]

I am like 99% sure your problem is throttles of EML computer, sometimes swapping throttles does nothing because both of them could be causing EML light but still allowing the car to run.
Need to start with throttles and then move on to EML.
PM me if you decide to have them rebuilt, then move on to EML computers which I also have pre programmed.

" One other symptom that we had for a little while was that if we put a charger on the car and let it sit for a while charging and then crank with the charger on, it would run on all 12. No EML light. Turn it off, turn off the charger, start it back up, and back to 6 with the EML light on. (we did load test the batteries and both are well within spec. 13 and change volts sitting still and 11.5 when cranking. They are also less than 2 years old and Interstates). "

Throttles can be watched for operation by key in on position do not engage starter. Remove rubber boot one person inside car moves accelerator says 10% 20% 50% 75% 100% second person watches interior of throttle body to see butterfly(brass disc) follow call out.

This is a real long shot.... what are the conditions of the fuse-able links in the trunk wiring and what is the condition of the braided ground strap at the motor mount? Have the contacts to fuses lost their conductivity due to tarnishing. I have had to put a very slight twist in fuse contacts and then move the fuses up and down multiple times to burnish the fuse contacts in the fuse holders.

EML not being supplied sufficient voltage can cause all kinds of weird issues .... there is something called voltage drop.

What voltage drop is, is loss of conductivity in tarnished or corroded connectors that cause loss in voltage in an electrical system.

A 12VDC system cannot weather voltage drop the way say 120VAC electrical systems can.

[Blaizefed]

And its Fixed. We ended up deciding to take Dragon850 up on his services and send him the throttle bodies to look at. As we were doing that, may as well send him the EML computer to test as well. Up to this point we had unplugged the EML computer in order to check continuity to and from, but had not actually removed it from the car. Once I did, and turned it sideways, about 2 shot glasses of crystal clear water poured out........not good........ So I took it apart, and found that sure enough, it had water damage to the circuit board down the bottom edge.

Sent both Throttle bodies and the now dry EML off to Dragon850, he rebuilt the throttle bodies and tested the EML unit, and sure enough when plugged into his car it did the exact same thing as on ours. EML light on and running on one bank. So there is our culprit. He has supplied a new EML unit, I bolted it in last night and fired it up today, and now it is running back on all 12 with no warning lights.

How the water got in there is a complete mystery. The cover for the ECU box is in place on this car and all the seals are good (again, this is a pretty nice car, not a rotten old shed). but after a months long diagnostic process, I am pretty happy to just see the back end of it. We are currently going over all of the seals and weather stripping to make sure we are not missing anything, then we are going to send it.

Anyway, I just wanted to put a pin in this for anyone who finds this thread in future. It looks like the original suggestion that an EML light means either a bad throttle body or a bad EML computer was proven totally correct in this case. And thanks to all of you for the help with spit balling ideas.

[LappingLuke]

Great news. Dragon850 is an instrumental resource keeping our cars running for sure!

[dragon850]

And its Fixed. We ended up deciding to take Dragon850 up on his services and send him the throttle bodies to look at. As we were doing that, may as well send him the EML computer to test as well. Up to this point we had unplugged the EML computer in order to check continuity to and from, but had not actually removed it from the car. Once I did, and turned it sideways, about 2 shot glasses of crystal clear water poured out........not good........ So I took it apart, and found that sure enough, it had water damage to the circuit board down the bottom edge.

Sent both Throttle bodies and the now dry EML off to Dragon850, he rebuilt the throttle bodies and tested the EML unit, and sure enough when plugged into his car it did the exact same thing as on ours. EML light on and running on one bank. So there is our culprit. He has supplied a new EML unit, I bolted it in last night and fired it up today, and now it is running back on all 12 with no warning lights.

How the water got in there is a complete mystery. The cover for the ECU box is in place on this car and all the seals are good (again, this is a pretty nice car, not a rotten old shed). but after a months long diagnostic process, I am pretty happy to just see the back end of it. We are currently going over all of the seals and weather stripping to make sure we are not missing anything, then we are going to send it.

Anyway, I just wanted to put a pin in this for anyone who finds this thread in future. It looks like the original suggestion that an EML light means either a bad throttle body or a bad EML computer was proven totally correct in this case. And thanks to all of you for the help with spit balling ideas.

Thank you for the shout out!
Glad I could help!
Cheers!

- - - Updated - - -

Great news. Dragon850 is an instrumental resource keeping our cars running for sure!

Thank you!
Happy Thanksgiving!