M30b34 conversion won't idle

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millisk

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Hi all!
I transplanted a M30b34 Ser#5550551 into a 1973 e9 CSA #2232522 and have not been able to get it to idle.
It starts on the cold start valve OK, then will only run above 1300rpm with throttle partially open.
It will only run briefly on the idle circuit between 750 and 900 rpm when warm and if the connector to the temperature sensor #13621709966 is removed.

The management system is the original Bosch Motronic Basic DME 0 261 200 002 with no oxygen sensor or pollution gear attached.

The following is a list of actions I have done to attempt to rectify this issue and I would welcome any suggestions that you may have to solve this problem.
Many thanks
Ken

BMW m30b34 Ser.# 5550551 Type Code: 5332
ISSUE: Engine won’t idle and hard to start.
Items tested or replaced.
1. DME tested OK
2. AFM rebuilt
3. Temperature Sensor. Pt#13621709966 new
4. Temperature/Time Switch. Pt#113621274630 new
5. Cold Start valve: Tested OK
6. Wiring Harness connections to DME: Continuity tested OK
7. Throttle Clearance: Adjusted to spec
8. Fuel Pressure Regulator: Tested OK
9. Position and Speed Sensors: Tested OK
10. Hoses checked for vacuum leaks. None detected
11. Spark Plugs cleaned. Evidence of overfuelling (black)
 
don't know the answer off hand, but as i remember, the e28 had an idle control relay in the glove box. when that relay went out on my e28, it idled high. on the other hand, i would think you need an o2 sensor to give feedback to the ECU
 
rsporsche said:
don't know the answer off hand, but as i remember, the e28 had an idle control relay in the glove box. when that relay went out on my e28, it idled high. on the other hand, i would think you need an o2 sensor to give feedback to the ECU
Click to expand...

Thanks! The motor came from a 1980 635i. It has one relay next to the DME (main power) and a second in the engine bay for fuel pump. These are working fine.
 
Australia

Interesting....

09/1980 M90 euro spec engine
9.3:1 compression
93.4 bore
Great engine for an E9

ECU is 0261200002
12 14 1 274 643
12 14 1 274 642 reconditioned
Production 09/80

Bert and I have spares for this.

How about a pic of the engine bay, injector part number, tps part number, resistance at ntc 2 and its Bosch part number?

Afm part number

A pic of crank at TDC and pics of the cam gear and flywheel when crank is at TDC?

Get a spray can of starter fluid too.

You will need a fuel pressure gauge and a volt meter.

You will need to rest your additional air slide valve - get 3 feet of wire and strip the ends.



With key on and car not running measure voltage at the coil. All three connections there.
Measure fuel pressure at the fire wall end while cranking and running
Pics of engine timing (cam, crank, flywheel)
Part numbers
Engine bay pics both sides
 
Last edited:
Test the ntc 1 also.
Keep it running for q minute and pull a plug- wet?
 
sfdon said:
Australia

Interesting....

09/1980 M90 euro spec engine
9.3:1 compression
93.4 bore
Great engine for an E9

ECU is 0261200002
12 14 1 274 643
12 14 1 274 642 reconditioned
Production 09/80

Bert and I have spares for this.

How about a pic of the engine bay, injector part number, tps part number, resistance at ntc 2 and its Bosch part number?

Afm part number

A pic of crank at TDC and pics of the cam gear and flywheel when crank is at TDC?

Get a spray can of starter fluid too.

You will need a fuel pressure gauge and a volt meter.

You will need to rest your additional air slide valve - get 3 feet of wire and strip the ends.



With key on and car not running measure voltage at the coil. All three connections there.
Measure fuel pressure at the fire wall end while cranking and running
Pics of engine timing (cam, crank, flywheel)
Part numbers
Engine bay pics both sides
Click to expand...

Thanks SFDon for those suggestions!
Donor car was imported from UK in early '80s.
Rebuild included 94mm forged pistons by http://www.specialpistonservices.com
Could not obtain them easily from anywhere else.
0.014" off head. Fully balanced.

Information obtained so far:
AFM Part# 0 280 203 013
TPS Part # 0 280 120 302
Fuel Press Reg Part # 0 280 160 214
Have checked crank and cam timing. Will send pics.
Have checked fuel pressure at firewall end, after filter. 36-40psi.
Will send pics of engine bay etc.
Plugs(Bosch standard spec) tend to be sooty black and only wet in cyls 3&4 when checked after cold start valve operates. Will do some more tests.
Engine runs at higher speeds until plugs tend to foul.
Questions:
1.What does this mean? "resistance at ntc 2"
2.Three connections at coil? Positive, Negative and ?.
3. rest? your additional air slide valve.
I have tested the slide valve and it closes fully after the specified time. What is the recommended opening setting at 20 Celcius?
 
Ntc 2 is water temp sensor
Last 3 digits on it are 026

Ntc 1 is air temp sensor inside afm

Pull coil wire out of tower in coil
You now have 3 connections to test: big nut, little nut and tower where coil wire to distributer
wire was.

Your plugs are fouling because you have disconnected your water temp sensor.
Infinite resistance reading to Ecu tells computer it is -100 degrees water temp and floods engine with gasoline
 
Test pins 6 and 22 on your afm for resistance.
Should be 2500 ohms at room temp.
Same for water temp sensor for motronic
 

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matthewp said:
you're not tempted to run a programable ecu ? they're quite cheep on ebay.
Click to expand...

I have investigated Autronic (expensive, requires mods but good), Haltech(mid range, simplest to fit), Wolf(dubious support and provenance).

What brand would you suggest? Do you have one in your car?

At the moment I want to fully eliminate all possible reasons why it doesn't work with the original gear. After all, there's still plenty of engines working that way.
 
Here on the west coast we do megasquirt.
I've fired up and tuned 5 in a week. Gets to be routine.
What's the number on those injectors and were they bench tested before you installed?
Can you hear each one click?
If two are wet and 4 dry......
Try a noid light in each plug and tap each one with a hammer and screw driver.
Ohm out one injector please.
 
sfdon said:
Ntc 2 is water temp sensor
Last 3 digits on it are 026

Ntc 1 is air temp sensor inside afm

Pull coil wire out of tower in coil
You now have 3 connections to test: big nut, little nut and tower where coil wire to distributer
wire was.

Your plugs are fouling because you have disconnected your water temp sensor.
Infinite resistance reading to Ecu tells computer it is -100 degrees water temp and floods engine with gasoline
Click to expand...
Not sure why engine idles better when water temp sensor is disconnected after warm up? Appears to go against your theory above.

Don,
Update on actions:
AFM resistance 6&22 = 2560 ohms
Injectors #0 280 150 201 = 2.7 ohms
In the BMW Tech Data Chart it appears that these injectors are not the standard ones and were fitted to the M6. Standard is #0 280 150 714. I have some from a 7 series that are also 0 280 150 201. Higher flow rate 235 cm3/min.
Water temp sensor # 0 280 130 026 = 2510 ohms (Supercedes 0 280 130 023)
Coil Voltages with reference to ground. +ve 8.8, -ve 3.9, Centre HT 8.8
Injectors have been cleaned and bench tested before installation. Tested with noid light after installation.
Your NTC chart is too small to read.
Pics to follow in separate message.
 
Engine bay images.
 

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Write this down somewhere......

You can never never never use low impedance injectors on a high impedance system.
It overheats the drivers and the engine won't work.

You MAY use high impedance injectors on a low impedance system.



"It is not recommended to use low resistance injectors in a saturated driver circuit.
The additional amperage required to open the injector can overheat the ECU causing permanent damage. In addition, the injector’s opening and closing times may become unstable creating rough engine operation and possible lean misfires.

It is possible, though, to install high resistance injectors in a peak-and-hold system since the amperage needed to open the high resistance injector is lower and within the limits of the peak-and-hold driver circuit."



https://www.google.com/search?q=low...+ecu&ie=UTF-8&oe=UTF-8&hl=en-us&client=safari


http://users.erols.com/srweiss/tableifc.htm
 
I think you need to double check your reference to the 714 injector- that is a high impedance injector that wasn't in use when your car was produced.
I believe early motronic used the 201 injectors as did later m cars.

Recheck your coil voltages with the - wire disconnected.
Your voltage readings are off by a huge amount.
 
Please verify you do not have a dropping resister to your coil installed.

With the - wire removed you should have the same voltage at all 3 test points
Battery voltage minus 1/2 volt or so
Plus, minus and tower all to measure same.
Connecting minus side and getting a low reading on an electronic driver means you have a short on that leg.
 
Let me clear this up- your plugs WILL foul if you disconnect your sensor

Your plugs are fouling because you have disconnected your water temp sensor.
Infinite resistance reading to Ecu tells computer it is -100 degrees water temp and floods engine with gasoline
 
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