850i M70 M1.7 runs only on bank2 and even on this one it is rough. No codes - SOLVED

[PabloRock]

I didn't see you mention checking the rotors. I lost a bank and for the life of me couldn't figure it out. I had replaced distrib, rotors, wires, ect the year before so thought all that was good. Checked everything by swapping, but one of the rotors I had stripped and couldn't get out but it looked perfect. Actually ended up pulling the top end apart to check fuel and seal my intake manifolds. In the end, removed rotor with a pair of vice grips and low and behold, burnt out on the other side. At least I ended up with a smoother running car and nice painted valve covers. (note to self; don't use and allen key to do the rotors just because it's handy).

[sshivaram]

Please do me a favor: go get a simple clamp meter to measure current flow. (I recommend the one i use, https://usa.banggood.com/MUSTOOL-MT3...p-1597324.html )

do these: connect back everything.
1. measure if current is flowing in the ignition leads.
2. Check the voltage at each of the injectors (they should be at 12 volt, and dip to 0 causing the flow of current when firing) when ignition turned to ON and not Running yet.
3. we will assume air is flowing into each of the cylinders.
4. Check fuel pressure, very important !

These are extremely basic things. Start from scratch , connect back everything and follow my leads. Thank you !!

[cartoonz]

OMFG! The infamous magic clamp returns.
Better check the popcorn stock... heh heh

[sshivaram]

OMFG! The infamous magic clamp returns.
Better check the popcorn stock... heh heh

boss, always happy to explore other options to positively verify flow of current in the ignition cables , am all eyes if you want to type ! I had used an inline tester and it wouldn't accurately tell me if the current was flowing when it wasn't connected.

[Fx323i]

OK guys, I now know I was starting with loads of improper information from the customer and previous service places. I again measured the resistance of the ignition cables running to cyls 6 and 12 and this time I also was bending the cables and found out that once bent, they are bad.

[shogun]

Perfect, thanks for the info, Martin. so the ignition cables 6 and 12 were the problem.

[Timm]

Glad you got it sorted!

[Fx323i]

Shogun: There were several problems. The car arrived as this:
Cyls 1-6 not working at all (this was the fuel pump giving not more than 1 bar of pressure)
Cyls 7-12 working but very rough, it was not possible to gas it over 1500 rpms and during this the engine died

There were clogged injectors and spark plugs with improper resistance.

After splitting the fuel line from the working pump to both banks the engine was running smoothly on bank 2, bank 1 was not working at all (started on all 12, after then ignition fault was recorded on one bank). Then we started to move components from the working side to the non-working side. No change. Put the car aside for 4 days and just thinking about it. Day 5 with no change made, bank 1 was working for 2 seconds and died, bank 2 was working. Let it sit till the afternoon and then both banks were working for 2 seconds and then died. This made me decide that the cyl 6 and 12 spark wires must be wrong as I had already measured them but not including bending and the CID sensor lines from connector to DMEs were both checked fine. Also the CID sensors were measured on resistance with almost no difference from the spec, crankshaft sensors were measured by oscilloscope and also revolutions of each one were visible on the diagnostic.

All in all, yesterday night I ordered two sets of spark wires meant for E32 735i with CID sensors, aftermarket made in our country and I have a good experience with these from the times 18 years ago when I owned an E30. So I ordered them and even before measuring the original cyl 6 and 12 wires, I just put the new cyl 6 and 12 wires in and you see the result. After I rechecked the original BREMI wires again with bending and saw that my first measurement was not as good as I thought.

Anyway, these distributor systems are now hard to find here and I am glad that the problem with a car which costed the customers 2 years of life, car in 3 different workshops during all that time, and we found quite all the problems within 3 working days during 3 weeks of checking - thinking (and reading a lot and asking you guys). I am just wondering how the previous service places could not have found at least the fuel pressure issues as the all claim they checked it. One of them even claimed they tried to use an extra fuel tank with new pump outside of the car feeding the engine. After seeing our results, I can not simply believe them. They even claimed that the spark wires were replaced with new ones a year ago, which was also not correct.

You also may have seen in the video that the car thinks it is on reverse while actually in parking position so I know we will need to adjust the shifting cable. The information about gear on cluster and on the gearstick cover are not the same.

[CD05001CIA]

OMFG! The infamous magic clamp returns.
Better check the popcorn stock... heh heh

Orville Redenbacher Popcorn is a subsidiary of Conagra Brands so... as of Sept 1, 2021 - 11:18am EDT

Market Summary > Conagra Brands Inc
NYSE: CAG


$33.12USD−0.0100 (0.030%)
today

- - - Updated - - -

YAY ! ! ! Got it sorted out.

[LappingLuke]

OP, glad you got it figured out!

side note: Holy crap a clamp on meter can also measure the current in a spark plug wire that only lasts around 1 millisecond! UNREAL

[sshivaram]

OP, glad you got it figured out!

side note: Holy crap a clamp on meter can also measure the current in a spark plug wire that only lasts around 1 millisecond! UNREAL

Made this video just for you my friend. Common lead to distributor shows 0.2A, and each individual ignition cable going to spark plug shows 0.03A (divided by 6 cylinders approximately, rounded to its best resolution). It shows the True RMS reading, so can read it off the leads easily. its not noise , it can only measure current inside the wire in the armature, and not anything outside by its design.

https://www.facebook.com/10000226096...4945673120446/

[Fx323i]

So what was left... Before putting everything back together I also went and inspected for the battery drain. The total consumption after entering sleep mode was 3,6A.

- 3A out of it was radio as it was not connected to DC12V for memory and ACC to radio itself.
- 0,6A was the fuse #42 which leads us to the famous capacitor problem. I pulled RM and GM modules and replaced the capacitors in both of them.

WhatsApp Image 2021-09-06 at 14.11.16.jpegWhatsApp Image 2021-09-06 at 14.11.09.jpeg

Tomorrow I will put these back in and see if the battery drain continues. The radio connection is corrected already and with these modules out, the consumption is not measurable by the clamp current meter.

[Timm]

Good luck!

[Fx323i]

I had to read a lot again about the E31 sleep mode process but finally I need to say, the car is now not even draining the batteries. Its sleep mode current draw is below 30mA.

So all in all, everything that the owner needed to solve is done. I could imagine another 2 years on this car as it was abused a lot. But that is not our task :-)

[CD05001CIA]

I had to read a lot again about the E31 sleep mode process but finally I need to say, the car is now not even draining the batteries. Its sleep mode current draw is below 30mA.

So all in all, everything that the owner needed to solve is done. I could imagine another 2 years on this car as it was abused a lot. But that is not our task :-)

This e31 owner was lucky to find you. Will he be grateful, time will tell.