m30 running rough (NOW WITH VIDEO)

[yert315]

I had a similar issue when I used the m20 harness. Never fully figured it out. However, I swapped over to the b35 harness and it ran like a champ.

[csermonet47]

For the engine to run the following conditions must be met:

Power on DME pins:
27 Start Input
18 Un-switched Power input
37 Power Input from Main Relay

Ground on DME pins 2, 14, 19, 24

Timing data from the CPS on DME pins 47 & 48 from a rotating engine

To have spark power must be present at the coil positive and ground pulses
from the DME's pin 1 must reach the coil negative. Power to the coil is
controlled by the ignition switch via C101. When checking for spark, use the
output lead from the coil to eliminate the distributor, rotor and plug wires.

To have injector firing power must be present at each injector and ground
pulses from the DME's pin 16 (Bank1) and pin 17 (Bank2) must reach the
respective injector bank. Note that the injectors are wired as two banks of
three. With cylinder 1,3,5 being bank 1 and 2,4,6 being bank 2. Power to the
injectors is controlled by the main relay. Injector firing is best checked
with a noid light.

The fuel pump relay must have power on pin 86 (relay coil) from the main relay
output (pin 87) and power on pin 30. The DME will ground pin 85 to turn on the
relay and power the pump(s) via pin 87. Of the above, only the fuel pump power
is fused. So if the there's power at pin 87, but not at the pump, check fuse
11.

The main relay and DME pin 18 receive power from the smaller of the two wires
that connect to the battery's positive terminal. That wire incorporates an
in-line fuse. When the DME is presented with a start signal, it grounds the
main relay pin 85 and furnishes power to the fuel pump relay, injectors, and
DME.

Troubleshooting:

Disconnect the battery and the DME cable. Then:

1) Disconnect the coil negative and check continuity from that connector to
DME pin 1. Also verify that from DME pin 1 to ground is an open circuit.

2) Check the resistance across DME 47 & 48, which should be 500-560 ohms. If
the CPS is dismounted, the resistance can be seen to change from about 500 to
540-560 ohms when a ferrous object is brought to the face of the
sensor. Neither pin should be grounded.

3) Check for continuity from DME 36 to main relay 85 and from DME 3 to fuel
pump relay 85.

Reconnect the coil, remount the CPS (air gap should be 1mm), plug the
relays back in, reconnect the DME, and connect the battery. Then do the
following checks:

1) With the key off, verify that power is present at DME pin 18 and main relay
86 & 30.

2) With the key on, verify that power is present at DME pin 27 and pin
18. Power to pin 18 is from the main relay and there should be power to the
injectors and fuel pump relay.

3) With the key on, verify that no voltage is present at the DME grounds (2,
14, 19, 24).

4) Verify that power is present at the coil positive and at fuel pump relay
pin 30. Those get switched power from the ignition switch via C101.

The engine will start and run (if poorly) with only those connections to the
DME in place. The other signals from Cylinder ID, AFM, temp sensor, etc., are
necessary for proper operation. But they won't prevent the engine from firing.

IMPORTANT:

A power check means seeing a voltage within about a tenth of a volt of what
you measure across the battery terminals, which should be at least 12.6v on a
charged battery.

A continuity check means seeing less that 1 ohm of resistance.

An open circuit means seeing a resistance of at least 100k ohms.

A good quality auto-ranging digital multimeter will make these tests much
easier.

Try this to make sure all the harness stuff is correct.

Here is the DME pinout: https://docs.google.com/file/d/0B97_...zg3/edit?hl=en

[tfritz]

^thanks! I'll check all that tomorrow

[tfritz]

Okay, I put in a different ICV and may have had the ICV and TPS plugs switched :oops:....It starts perfectly fine and idles good but still have no throttle, when I give it throttle it just bogs down...TPS???

[Doughnut]

Okay, I put in a different ICV and may have had the ICV and TPS plugs switched :oops:....It starts perfectly fine and idles good but still have no throttle, when I give it throttle it just bogs down...TPS???

TPS will cause this issue, remove it and turn it with your finger, it should make a little "click" noise at idle position, and should move smoothly through its rotation.

AFM will cause this problem too but you have a MAF so...

[tfritz]

Well im pretty sure the MAF is toast, I tested for resistance and get nothing...
Also not getting any power to the tps plug...tps has a little click when turned, just no power going to it...

[tfritz]

Okay, after talking with Brodi from miller, the MAF checks out. Also got a brand new tps. I STILL have this dang surging issue!!

[Jean]

Surging can be caused by the idle control hose collapsing as well, double-check the hose from the icv to the intake manifold that goes down under the wiring harness.

[tfritz]

ICV hose appears to be fine

[tfritz]

Also just tested fuel pressure and it is about 39-40 at idle, then I unhooked the vacuum at the regulator and the pressure jumps to about 44-ish.

[csermonet47]

If harness stuff is good, you have no vacuum leaks, and you have good fuel pressure, it can only be a few things. Have you done a compression test to verify all those numbers check out? You need 3 things to run properly. Air, fuel, and spark. Make sure all your plugs are firing correctly and have good spark. Take them out and look at them but don't try to run the car without a plug in without pulling the fuel pump relay (it is a good way to burn your garage down). Plugs can tell a lot. Also make sure all your injectors are firing properly. I bought rebuilt injectors and had one stuck open that caused all sorts of issues. Verify you are getting voltage to all of your injectors. Checking your timing wouldn't hurt either. Is the car smoking at all? You can also start swapping parts out for known working units. CPS sounds like a good place to start. If you don't have access to known working units, there are tests in the E34 Bentley book for them. If you don't have the Bentley, PM me and I can send you the test procedures.

[tfritz]

Just swapped the m20 harness today for an m30 harness and it fixed the issue!

[yert315]

called it. glad everything worked out!

[csermonet47]

Does it do mad burnouts?

[tfritz]

^haha haven't driven it yet. Still needs the fan wired up, clutch bled, exhaust ran, and a few other little things.