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Subject: rough idle/no power M70 -basics to check Author: shogun (moderator) : member since March, 2004 : 12550 posts Posted on: 2006-08-30 10:39:44

Basic points for fault analysis at a 750i/iL E32 for the DIYer

engine problems such as rough idle/no power:


- 1. -
The easiest way is to have a possibility for fault analysis at the dealer with a DIS, or a PEAKE fault code tool, or the stomp test.
The delaer testing computer is of course the best and most comprehensive one and gives online results while the engine is running, while for example the PEAKE just can show stored results in the system. As for Peake tools, see www.peakeresearch.com
Fault code test/stomp test

see procedure on my website

-2.-
Important is that the EML light in the dash goes on for about 2 seconds when the ignition is set to position 2, after that it should disappear. Actually there are 2 bulbs for the EML, and one of it functions as a resistor for the other one.

detailed introduction to EML, how it works and what items it controls.

Cockpit/cluster repair:

If the EML light does not come on when ignition is in position 2, the engine will always run in limpmode. So this has to be repaired. Not many professional shops know that, they just replace the complete cluster or ECU modules because of lack of knowledge.

Remove the cluster from cockpit, see Johan and Sean's page.
Pay special attention when you have an airbag, all mentioned on Johan's page. Link on my website if you do not know it.

Repair method:
The EML light should come on when engine is started in ignition position 2 for about 2-3 seconds and then go off. This is a kind of test for the 2 bulbs inside the motherboard of the cluster. One bulb acts as a kind of resistor for the other, to speak in my no-electric expert words.
People have paid hundreds or thousands of $ to repair shops because they replaced unneccessarily MOTRONICS, EML and other parts of the car, as the car was in limp mode and they could not solve the problem.
Limp mode, also known as failsafe mode, limits throttle openings etc and runs off a preprogrammed setting, limits rpm and speed as well...
Vmax after 2 minutes approx.50 kmh in 3rd gear, at max. 1500 RPM, no ability to climp uphill and so on.

A member of 7er.com has just made a write-up with pics. Of course it is in German, but the pics are most important to understand.
Main points I just translate in brief into English, I will omit the general info on how to remove the cluster from the dash, and other points known to all of you which are regular visitors on this board.

Pin 16-17, the only connected soldering points of the "white" plug are to be connected to the "upper contacts" of the 2 EML lights.

Option: Pin 12 of the "brown" plug to be connected (soldered) with the "lower contacts" of the EML lights.
As connector he used hot glue.
Leave cable long enough to assemble the cluster again.

Notes:

No guarantee for correct translation. It is your car when you repair it.
Description is based on a cluster from a 750iL from 05/1989.

If you are not able to see the pics in the link to the German board, you might have to register first. Easily done, no cost involved, and they have a very good repair page, done and maintained mainly by Erich = shogun ;-)

http://www.7-forum.com/forum/showthread.html?t=41084
http://www.7-forum.com/forum/attachment.html?attachmentid=5109
http://www.7-forum.com/forum/attachment.html?attachmentid=5110
http://www.7-forum.com/forum/attachment.html?attachmentid=5111
Pins location:

1 26
2 25
3 24
4 23
5 22
6 21
7 20
8 19
9 18
10 17
11 16
12 15
13 14

- 3. -
In case the EML works fine, check the gear and trans mode in the cluster. If they are not shown, engine runs in limpmode.


repair procedures

- 4. -
Visual check of the intake system.

Use brake cleaner and spray it when engine is running in all areas around the intake system, but NOT into the air intake duct directly. If the RPM changes, you have an air leak somewhere. Check all the rubber connections in the intake system

- 5. -
Should all this not help, check by cylinder banl to allocate the side of the engine which makes a problem. Remove one after the other the connector from the throttling valves and check if the engine stops when one is not connected. Can be done while engine is running, connecting and disconnecting.
In case one cylinder bank stops the engine, concentrate on that side. But remember, the intake system you see in the car on the passenger side actually goes into the cylinder bank of the driver side and vice versa.
Start changing parts from one side to the other, throttling valve, MAF. If the fault moves to the other side, you have the culprit.

- 6. -
I so far nothing could be found, check the area of the oxy sensors. Remove one plug of the 2 after the other, if a big change in engine running, it could be the sensors or one of them.

-7.-
All this porovided that you already have made the basic checks such as distributir caps and rotors (often the first ones are still inside), crankshaft sensors, cylinder identification sensors, spark plugs etc.

A good help is the ECU pinout, where you have the data you should be able to measure

details here

A Bentley Repair Manual is a must for you, as there are many data, although sometimes we find mistakes.

Wiring data and other hints you

find here under electronics

Please feel free to add any suggestions here.

shogun >>E32 750iL<< 11/88
7 series Tech tips
http://tinyurl.com/3486c

• rough idle/no power M70 -basics to check (url) - shogun 2006-08-30 10:39:44 (4925 views)
  • fantastic post - very useful to all M70 owners (nt) - E31Gill 2006-09-01 04:46:43 (369 views)