E30/E28: Faulty AFM (Air Flow Meter) repairs, worn carbon-track quick fix

** FOR ADJUSTING AFM AIR/FUEL RATIO SEE THIS POST **

The AFM or Air Flow Meter uses a metal flap that is opened air entering the engine to move a brass arm up and down a carbon-track. The position of the arm along the carbon track alters the electrical resistance through the circuit and this lets the ECU know how much air is coming in, so it can deliver the right amount of fuel to the injectors. The E30 uses a BOSCH AFM unit, also used in many other BMWs with Motronic or Jetronic injection systems.

The analog electrics in the BOSCH AFMs rarely ever fail, but there are two areas that are failure prone after higher mileage - a worn carbon track and a faulty air-temperature sensor.

E30 318i: Correct Temperature Sensor fitted (Brown Plug) + wiring/loom issue

The temperature gauge in the dash has not worked since I bought the E30, which was a little worrying on my 250 mile drive home, but the car does not overheat. Oh, it has some issues with the cooling-system, like the heater-matrix pipes fitted incorrectly and an air-lock at the back of the head, but hey it doesn't overheat. Still though, I thought it best to get the bottom of the faulty temp. gauge for peace of mind, particularly with summer coming / just about here.

The M40 has two separate temperature sensors that are independent from one another. The temperature gauge works from the 'Brown plug' sensor to the rear of the head [right in pic]. The forward sensor is the 'Blue plug' [left in pic] and that connects only the DME (ECU) to tell the car if the engine is cool or warm to help with cold-start procedures. A single sensor cannot be used for both purposes on these older engines as the resistance value ranges required for each function differ, the DME being a digital circuit and the temp. gauge still working in analog. [You can read more about this on the E30 Zone Wiki HERE].

MULTIMETER TESTING:

The temp. sensors can be easily tested with a multimeter set to 20k ohms resistance. 

The Blue plug is a two-pin sensor, so test across both terminals with the multimeter and you are looking for a reading of 4-4.5k ohms for a working sensor. This sensor and plug can be accessed easily without removing any parts from the engine.

The Brown plug though will require removal of the lower inlet-manifold to access the sensor for testing or replacing. This is a single pin sensor, so place one probe of the meter to the terminal and the other to a ground-point in the engine bay or against the block/head. Expect a reading of between 1k and 1.5k ohms for a working sensor. To test the Brown plug sensor without removing any parts from the engine, you can apply the multimeter to Pin 4 of the C101 connector (main wiring loom plug in engine bay) which is easy enough to get at, or at Pin 26 of the blue connector to the right side of the instrument binnacle, though the binnacle will need removing to do this.

WRONG SENSOR / CONFUSING WIRING LOOM:

All M40 engine wiring looms use a single pin temp. sensor on the brown plug that earths through the engine block and have only a single wire in use leading to it. Some looms, using components destined for other BMW models, are known to have a second wire leading to the Brown plug temp. sensor which is redundant on the M40 motor, though this is rare and seen more often on 6-cyl. M20 looms. My car has one such loom, however and I realise that this is what has caused confusion in the past and led to the wrong sensor in fact being fitted...

Upon inspection, the rear temp. sensor fitted to my E30 is black, not brown and has two terminals. The second pin means that the sensor body earths back to the loom and not through the block so, if the redundant earth wire in my loom is not connected to a ground-point then the sensor was open circuit. I guessed that someone had ordered a second Blue plug sensor by mistake and fitted that, but it turns out the part number doesn't match and the sensor is for a completely different model engine entirely. The reading from the multimeter was over 11k ohms, something like 7.5 times what it should be! That sensor was never going to work with the E30 temp. gauge circuit whether it was earthed or not.

I ordered the correct single-pin sensor with the brown base from mr-wiper on eBay, who also supplied my Bosch spark-plugs. It was only £7.69 delivered. My temp. gauge now works, but this may also be due in part to removal of an air-lock at the back of the head due to a heater-matrix problem so coolant is now flowing properly round the area of the sensor. 

A BIT MORE ON WIRING LOOMS:

Brown / Violet, brown being the main colour, denotes that the power source provided from the temp. gauge circuit is earthing through this wire and does not need to be a closed circuit back to the gauge. The other wire is either not wired in to the loom or goes to a body-earth anyway, so earthing the sensor through the block will make no difference. This colour coding is the same for all wires in all BMW looms, I would imagine most cars are the same.

E60/E61: Hidden OBC Menu in Instrument Display - view R/T measurements + CANBUS data

There is a hidden way to access real-time CANBUS data through the instrument binnacle. The guide here [written by scoopz for m5board.com] mentions the E60 M5, but I used this on a 530d manual and 525d auto, so it does cover all E60/E61 models. It may work, or there may be a similar system for Fxx Series BMWs, but I have not had a chance to examine this yet.

Measurements that can be viewed include true engine temperature, true engine RPM speed, true vehicle speed and loads of other bits of information that the CANBUS system records, but the iDrive does not normally display.

LINK: https://drive.google.com/open?id=1nHxeTpZLO2X5PkZQse10ureUOTBdBJx6

GUIDE: [written by www.scoopz.com for m5board.com]

*ACCESS PDF GUIDE FOR ACCOMPANYING PICTURES*

To access the menu follow these steps:1. Ensure your engine is OFF but ignition is in stage 2. (For

     those with comfort access just press the start/stop button
     twice once in the car without your foot on the brake)

2.Press and hold the odometer reset button (from now on I shall just call it the button) for 6 seconds, during which it will

show an oil icon, then a warning triangle. Keep holding and release when it shows: 01.__ FGSTNR

After a second or two the 01.__ will be updated with 01.00 and the last 7 characters of your VIN/Chassis # will show: 01.00

FGSTNR

CU12345

     Make a note of the numbers, this is important as you will need
     them in a minute to unlock all the menus because at present you
     can only access menu 01.__, 02.__ and 19.__
Now that you have made a note of your VIN number you need to add all the individual digits together so if your VIN was CU12345


Then you need to do:
1+2+3+4+5 = 15
This number [15 in this example] is you magic unlock number and is needed for step 6.
Press and hold the button for two seconds until it shows(press button 2 seconds)
01.__
Whilst it is displaying 01.__ repeatedly press the button to cycle through the menu’s incrementally:
01.__
(press button)
02.__
(press button)
03.__
(press button)
until you get to 19.__ at which point stop and wait for it to show
19.00
LOCK: ON
CODE: 00
     Now press the button repeatedly to increment the CODE eg:
(press button)
CODE: 01
(press button)
CODE: 02
(press button)
CODE: 03
(press button)
...until you get to the number you calculated in step 4, your unlock code, in this example 15:
CODE: 15

Once you have reached your unlock code wait a few seconds and it should jump you back to 01.00 and all the other menus will be available.
There are 21 top level menus and some have sub-menu’s, for example:
01.__ 01.00
      01.01
      01.02
      01.03
02.__ 02.00
03.__ 03.00
04.__ 04.00
04.01 04.02etc
To change top level menu’s press the button for 2 seconds until the last two digits turn to underscores (XX.__) then release the button and quickly press the button repeatedly to increment through the top level menu’s, e.g.:
(press button 2 seconds)
01.__
(press button)
02.__
(press button)
03.__
etc
Once you arrive at the menu you want to go into just wait a few seconds and the two underscores will be replaced by double zeroes (XX.00) and every subsequent press of the button will cycle you through the selected menu’s sub menu:
04.__ (wait few seconds)
04.00
(press button)
04.01
(press button)
04.02
(press button)
04.03

10. Some menus don’t have sub menus so waiting for the to display




XX.00 and then pressing the button again will activate that feature, try it on menu 02.00 and it will carry out a dashboard

test and move all the needs. Press and hold the button for two seconds until the last two digits turn to underscores then release and keep pressing the button until it shows:02.__

     (press button)

02.00

     (press button)

     Dashboard will do strange things.



Ok so that’s a run down on how to access the menus and move around the different levels of the menus. I systematically accessed each menu and it’s sub menus and photographed each one to create a rough guide as to what is shown, most things I haven’t got a clue what they are but some things like current true speed, rpm and rpm limit are useful.

E36 316i Compact: chilling update...

Well, the new head gasket is on and the car is running like a bag of spanners. I think the slapdash chain refitment may have knocked the timing out slightly. I shall have to break out the Gunson timing gun kit I bought for the E21. Oh the joys of £200 Beemers...

The cooling issue appears to be sorted, though with the thermostat removed by the previous owner it's now running a tad on the cool side. I grilled the car the 2 miles to work this morning and could only muster a 1/4 from the temp. gauge. Ah well, a new stat can't be much.