M5 won't stay running - Page 2

Sub8 · 31st July 2012, 12:12

The MAF does not control any `flaps`.

The voltage readings given are presumably for the Porsche engine. As such they willl not apply to an M5.

Have you replaced the HEGO sensor? Have you cleaned the plugs they will be fouled from your previous running.

crowdaddy · 31st July 2012, 15:17

See...I thought that it controlled to variable positions of a 'flap'. Maybe I just like saying flap. Just throwing things out there dude. This is a perfect example of how I should just keep my mouth shut...but I just want to be loved.

And the Porsche thing...ya I figured the values would be wrong, but the idea...checking the voltage or what-have-you is a good place to start learning about these things.

HEGO sensor? Do you mean the o2 sensor?

Sub8 · 31st July 2012, 15:23

You may be thinking of the even earlier L-Jetronic Bosch control system.

This used an `L` shaped flap with a spring in the airflow. More airflow moved the flap more and gave a higher load reading. Used on original Golf GTi I think. Oh and rubbish! Next step was hot-wire MAF like `ours.

As Mr Olias would say, its all love on the M-forum! Apart from people saying sillly things about making a million horsepower with addition of a magnet under the parcel shelf.......

And yes 02 = HEGO (Heated exhaust gas oxygen sensor)

Amonsta · 1st August 2012, 02:09

Quote:

Originally Posted by crowdaddy

At the least, learn how to test the MAF and be sure before you start buying things. I read somewhere that you can check the voltage and it would give you an idea of how the wire is holding up.

Found this relating to a Porsche, but same thing...maybe...lol:

MAF TESTING - DIRECT VOLTAGE METHOD

0. Remove the LH connector and lookup the MAF output signal and ground signal. Connect a good DVM to measure the output. Put the DVM into mV mode and keep a spreadsheet or note paper on standby.
1. Ignition on
2. Engine not running
3. On each MAF measure DC voltage between
pin 3 (ground) and pin 5 (signal)
4. Reading should be 1.75 V. The closer to 1.69 V the better. the dirtier the MAF the higher the voltage will be.
5. Start the engine, and drive the car until fully on operating temperature.
6. Re-test 4) Value will drop to approximately 1.69 V.
7. Make a full test cycle at idle, running various rpm's as indicated in our spreadsheet. This gives a good insight of the output compared to our reference MAF and other benchmarks.
8. After running the engine over 3500 rpm you can see the MAF do a burn off cycle. You need to remove the air filter and air filter box to be able to see this. It is visible in a low light environment.
If this procedure gives a reading in step 4,6 or 7 that is outside tolerance the MAF is definitely contaminated or otherwise damaged. Possibly the electronics have drifted from specifications.

I would imagine that the vacuum lines aren't the issue or the removal of the MAF wouldn't have changed anything. Maybe one the experts will chime in.

The flap that the MAF controls may just stay open all the way when the MAF is not hooked up. Just a guess. Or maybe it's getting stuck in various positions and contributing to the problem.

Trying to understand how the MAF being unhooked would allow the engine to run properly. Maybe its a faulty flap. Or the potentiometer that controls the idol maybe? Did you witness the car running without the MAF? How did it sound?

No I didn't hear it run. The guy at the shop just informed me that it did. He seemed to think the maf was the culprit. I didnt put a new 02 sensor in I will add this as an option. I just really wanted to start with less expensive things though so 02 1st I guess.

Guys I really appreciate the input and help thus far!

crowdaddy · 1st August 2012, 04:19

I would love to actually solve the problem, but it looks like, as I refer to a system not even on our cars anymore and the super technical "flap"

, Sub8 will lead you down the correct path of the "super long acronym" o2 sensor. It seems logical to me. Hope it works.

If not...I have a great theory about a possible short in the time circuits. Have you made sure your flux capacitor is...fluxing?

Amonsta · 1st August 2012, 06:19

I'm going to start tomorrow. I'll report back Soon!

Sub8 · 1st August 2012, 10:33

You also need to disconnect the battery for a period of time (10mins) to clear any adaptive values from the PCM. Check / clean plugs at same time.

Then when (if!) the engine gets hot the PCM will re-learn idle control values and fuel trim (assuming HEGO is OK).

Bondy · 1st August 2012, 14:33

Quote:

Originally Posted by Sub8

As Mr Olias would say, its all love on the M-forum! Apart from people saying sillly things about making a million horsepower with addition of a magnet under the parcel shelf.......

Have you got a picture of the location of this magnet? I can't see anything apart from this thing.

Amonsta · 2nd August 2012, 05:46

So under further inspection the maf has been tampered with. It has the previous owners name on it. Not sure what was done, but something has been done. No leaks found thus far.

Sub8 · 2nd August 2012, 09:08

Perhaps the MAF has been `refreshed` allready? Maybe worth giving injection labs a call to see if it was them?