1989 750iL Progress

[shogun]

Did you test all the sensors already like coolant, air intake etc?
I have read about rare cases where the DME or EML get too hot and damaged, on the E31 forum they repair EML units https://www.bimmerforums.com/forum/s...or-Replacement
Do you have spare DME and EML for testing? Of course, just a shot in the dark, can be many things.

[SergeBMW]

They all tested good. The issue is isolated to bank 1 (passengers side).

Erich: I do not have a spare DME but is it possible to swap one with the other to see if the issue follows the bank? or are they individual to each bank? My other EML is kaput, car won't start with it, the one installed was a replacement from ebay.

So far I have done the following
- Swapped MAFs, issue does not follow
- Disconnected MAF while running, car shuts off
- Distributor and rotor are clean and still new
- Checked the coil resistance and it checks out according to the technical manual. Compared to Bank 2 and it was the same
- Checked all spark plug cables, they all read approx 5.95-6.15k ohms. Number 4 cylinder is around 6.25k ohms. Not perfect but not horrible either. I believe the tolerance was 10%.
- New coil to cap wire


I ran the car today, was good, within 30 seconds now it started this same sporadic misfire. Sometimes within 10 seconds itll happen every half second, then for the next 10 seconds, nothing... smooth like a sewing machine. Reminds me of a hit and miss engine, thats it!! That's exactly what it sounds like. Bank 2 will not do this at all, runs very smooth on its own 6 cylinders. Wonder what could cause such a sporadic misfire, wonder if injectors can do this.


Continuing the hunt.

[shogun]

For a test you can swap bank 1 and 2 DMEs. Just mark them before that you are sure where they sit originally.
To test injectors you can pull from the fuel injectors with running engine the wire connector one after one and see if there is a change.
Also check one more both crankshaft position sensors and donuts for spec.

[SergeBMW]

I had been pulling one Injector off at a time while running that one bank only. Never found a single cylinder make any change. I had also checked the CPS and donuts, all seem good. The ignition cables are all a bit out of spec though.

Luckily I did end up finding one of the main issues. Decided to replace the fuel filters even though I have been procrastinating that. Both were different brand and dated 1990.. So most likely original. One of the poured out a fairly clean stream of fuel, while the other poured out a heavy chocolate milk or darker colored fuel. It was horrible. Fuel that kept spilling from the pump line to the filter has clean fuel coming form it. Checked both. Replaced the filters and the car ran so much better. Still had a slight miss, but no where near what it was, the car does not shake as before. It's still a bit rough but I'm sure that is due to old injectors and ingnition cables. I have a set of reman Bosch injectors waiting to go in. May do that this week. While I had my wheel off to change the filters, I decided to go ahead and swap in the E60 wheels wrapped in Michelin tires to see if that would cure my 70mph shimmy. Guess what.... It did. Only tested to 70 and so far it was gliding. Car feels more stable too and the they make the car look a bit more sporty. I love them.



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[SergeBMW]

Yesterday I had decided to throw in those Bosch reman injectors I have had laying around for a year. Now that I had the filters in and clean fuel on the fuel rail, I went ahead and did the job. Not too bad of a job. I would have saved time doing this while doing the intake reseal, but the filters were bad and was too tired to do them at the time. So the result? The car is smooth now, even after a long drive, spirited drive, or in the midday heat in Florida. The engine still has a very slight vibration, but I am positive this is related to old used ignition wires and coils. Eventually I will get to those.

I love sitting in the car and not feeling the engine. You can only feel it from under the hood, the new motor mounts do the rest.

Some photos:

IMG_20180819_155701.jpg IMG_20180819_160221.jpg IMG_20180819_160537.jpg


I was missing an injetor clip that holds it to the fuel rail, I dont think it was ever on there as I never removed that one specific rail before. The old injector was held in by the old o-ring, but the new injector did not stay in place, and when I cranked the car, fuel sprayed everywhere. What was I to do?? I was too excited to start it, I went and stole the clip from my E38s M62 engine, same clip.
IMG_20180819_164504.jpg


The obligatory fuel station photo:
2018-08-20 12.18.33 1.jpg

[shogun]

Very good, congrats. On Ebay search: fuel injector retainer clip.
Now you are almost ready for my limited special edition ignition wires in Ferrari RED http://tinypic.com/usermedia.php?uo=...c#.W3uAwO8UmUk

[SergeBMW]

It's tempting! I may want to jump on those chips of yours, but I'm sure the right thing to do would be to first buy the wires lol.
Regarding the cylinder identification wires, I ran mine with them unplugged for a moment, car ran fine. My understanding is this is only used during startup to push more fuel into just 2 injectors during crank instead of all 12?

Reason I ask is because if I can, I'd rather avoid having to remove any boots to install the sensors. Terrified of damaging the wires.


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[shogun]

If the engine runs fine now, don't touch it.
CID is explained in the tech info for 1.1/1.3, if there is no signal: CID sensor.............injectors are pulsed simultaneously


Cylinder Identification (CID)
An cylinder identification sensor is used to identify cylinder firing sequence. The sensor is connected around the HT lead of cylinder number 4 (4 cylinder) or cylinder number 6 (6 cylinder) adjacent to the distributor. As the HT pulses travel along the HT lead, a small AC signal is induced in the sensor and returned to the ECU. The ECU utilises an ADC to transform the signal into a digital pulse.

Fuel injection
The Motronic ECU contains a fuel map with an injector opening time for basic conditions of speed and load. Information is then gathered from engine sensors such as the AFS, CAS, CTS, and TS. As a result of this information, the ECU will look-up the correct injector pulse duration right across the engine rpm, load and temperature range. The injectors are arranged in two banks with injectors 1 and 3 (4 cylinder) or 1, 3 and 5 (6 cylinder comprising one bank, and injectors 2 and 4 (4 cylinder) or 2, 4 and 6 (6 cylinder) making up the other bank. Each bank is connected to the ECU via an independent ECU pin. The Motronic 1.1 & 1.3 multi-point injection system pulses the injectors semi-sequentially and once every two engine revolutions. During engine start-up below 600 rpm the ECU pulses all injectors simultaneously. Once 600 rpm has been attained and if the ECU has received a signal from the CID sensor, each injector bank will be pulsed alternatively according to which pair of cylinders are approaching TDC. If a signal is not received from the CID sensor the injectors will remain on simultaneous operation. However, if the CID sensor subsequently sends a signal to the ECU after the engine has commenced running, the ECU will pulse the injectors semi-sequentially after the next deceleration phase - even if the CID sensor then ceases to send a signal. During start-up from cold, injector pulse duration is increased to provide a richer air/fuel mixture and pulse frequency is also increased. In addition, the ignition timing is also retarded. Injector frequency & pulse duration and degree of timing retard depend upon the engine temperature both during start-up and immediately afterwards. If the engine is restarted within one minute of the first start occurance, less overall fuel is injected to reduce the risk of fuel flooding into the engine.

Fuel injectors
The fuel injector is a magnetically operated solenoid valve that is actuated by the ECU. Voltage to the injectors is applied from the main relay and the earth path is completed by the ECU for a period of time (called pulse duration) of between 1.5 and 10 milliseconds. The pulse duration is very much dependant upon engine temperature, load, speed and operating conditions. When the magnetic solenoid closes, a back EMF voltage of up to 60 volts is initiated. The fuel injectors are mounted in the inlet stubs to the engine inlet valves so that a finely atomised fuel spray is directed onto the back of each valve. Since the injectors are pulsed in two banks, fuel will briefly rest upon the back of a valve before being drawn into a cylinder.

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If the inductive sensor on the plug wire (CID) fails then it goes into gang firing, since the m70 is a semi sequential design meaning that it triggers the injectors of each side in 2 banks of 3 every other revolution, when it goes into the gang fire, then it triggers all six at the same time every revolution but decreases the volume of fuel by 50% .

The M70 M1.7 has a cat protect system, it will shut of the bank http://www.bimmerboard.com/forums/posts/1217375/

Motronic M1.7 Catalytic converter protection function, Ignition circuit monitoring
The ignition circuit is monitored by the cylinder detection sender (pin 16) on ignition line 6 (or 12). If it detects no ignition signal on ignition line 6 (or 12) , the fuel supply to to the relevant cylinder bank is cut out by shortening the injection signal. The sender monitors the entire primary side of ignition, and cylinder 6 or 12 on the secondary side. See page 19 http://www.wuffer.ca/MyFiles/S70EngineManual.pdf