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Old 07-08-2016, 03:16 AM   #1
daru
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Join Date: Jul 2016
Location: Sweden
Posts: 8
My Ride: 318i N46 -05(04/11)
Not stalling with unplugged MAF. Fuel supply OK then?

Troublesome 318i -05 with the N46 engine. Cranking and starting the car is OK. But after a few seconds
the cars starts to run very rough and then stalls. I have no fault codes (Autocom Cars diagnosis tool).

So far I have:
  • Checked for vacuum leaks around air intake (visually and with start gas).
  • New cam position sensors
  • New fuel pump
  • New fuel filter
  • New O-rings for vanos
  • New MAF (well, gave into laziness and wishfull thinking which is expensive!)

As far as I can understand this implies that there's problems with fuel supply.

My question is: Can I rule out fuel supply problems since the car works when unplugging
the MAF. In other words, when cars runs in backup mode there seems to be no fuel problems and can I therefore rule out fuel supply problems?

Last edited by daru; 07-08-2016 at 03:17 AM.
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Old 07-08-2016, 06:58 AM   #2
jfoj
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Join Date: Nov 2009
Location: Fairfax, VA USA
Posts: 22,858
My Ride: 330CiC, M5, X5, E93
If you have the original MAF put it back on and see how it works.

Chances are you have a Lean problem you have not identified. Most likely one or more vacuum leaks in the intake, crankcase or possibly the power brake booster.

Checking for vacuum leaks visually or with starting fluid is not an effective way to find leaks. Smoke testing is the best approach.

See these videos for idea -





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Solve your misfires, lean codes, rough idle - http://forum.e46fanatics.com/showthread.php?t=897616

Fuel pump failures - http://forum.e46fanatics.com/showthread.php?t=929501

Temp Info - http://forum.e46fanatics.com/showthread.php?t=964491

Hidden OBC Menu - Check Voltage, Temp, Fuel Level - http://forum.e46fanatics.com/showthread.php?t=239619

E46/E39 GM5 Door Lock Info - www.bmwgm5.com

Lower hose temp switch O-ring - BMW #13621743299
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Old 07-08-2016, 07:02 AM   #3
markusmarkus
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Stop throwing parts at the problem!!! Doing so doesn't fix the problem, wastes money and angers the BMW goddesses!! Find a reputable shop that specializes in BMWs.
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Old 07-09-2016, 02:41 AM   #4
daru
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Quote:
Originally Posted by jfoj View Post
If you have the original MAF put it back on and see how it works.

Chances are you have a Lean problem you have not identified. Most likely one or more vacuum leaks in the intake, crankcase or possibly the power brake booster.

Checking for vacuum leaks visually or with starting fluid is not an effective way to find leaks. Smoke testing is the best approach.

See these videos for idea -





Yes, I have the original MAF. I'll put it back.

So I will build a smoke tester to locate eventual leaks!

Thank you very much for answering!
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Old 07-09-2016, 02:51 AM   #5
daru
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Quote:
Originally Posted by markusmarkus View Post
Stop throwing parts at the problem!!! Doing so doesn't fix the problem, wastes money and angers the BMW goddesses!! Find a reputable shop that specializes in BMWs.
Oh, I know! As mentioned I gave into wishful thinking, laziness and the path of least resistance when I bought the new MAF.
To be honest I really did a stupid mistake having P0102 code because I had previously unplugged the MAF and then thinking: aha, MAF is broken. That and the fact that the car runs OK with MAF unplugged.

I will not let a shop fix this unless I have done all I can myself or I will learn nothing!

Last edited by daru; 07-09-2016 at 02:53 AM.
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Old 07-09-2016, 05:56 AM   #6
daru
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Built a smoke tester similar to this one:

Lots of smoke coming out! Major vacuum leak in (the inner, smaller) Valve cover gasket as far as I can tell.

Will try to fix that. And then do another smoke test to see if there's any other leaks. Smoke was fun!

Thank you very much jfoj for pointing me in the right direction. I have read a lot of your other answers and "big threads" which really makes this forum so much better!
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Old 07-15-2016, 08:59 AM   #7
daru
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So replaced broken valve cover gasket and did another smoke test to confirm it was tight. Then further smoke tests for CCV, power brake booster and through the intake with no visible leaks.

To my surprise I'm stuck with exactly the same problem!

The symptoms are:
  • Starts OK and then after a few seconds dies.
  • Can not rev up to more than ca. 2500 rpm.
  • Runs "ok" with MAF unplugged (i.e. safe mode)
  • No error codes

Any further help is much appreciated.

Regards,
David
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Old 07-17-2016, 07:24 AM   #8
daru
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Did another, better, smoke test for the inlet using better air sealing and pressurized air. This gave nothing.

Have do I test the crankcase? Is it sufficient to push smoke through inlet and then verifying by opening the oil filler and see smoke coming out?

If there's no vacuum leak I'm confused whats next to look for?
Back to fuel supply problem investigation? Or could one know that fuel supply is OK since it has enough fuel when running car with MAF unplugged?
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Old 07-17-2016, 11:17 AM   #9
OnTheFence
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What happened when you installed the original MAF.
I'm a n00b, but if car doesn't run with MAF, and runs fine without MAF, it sounds like a bad MAF.
Did you buy a cheapo one?
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Old 07-17-2016, 01:12 PM   #10
daru
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Join Date: Jul 2016
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Quote:
Originally Posted by OnTheFence View Post
What happened when you installed the original MAF.
I'm a n00b, but if car doesn't run with MAF, and runs fine without MAF, it sounds like a bad MAF.
Did you buy a cheapo one?
I experienced exactly the same symptoms with both old and new MAF. It was a expensive Bosch exactly like old one. Now the old one is installed. As far as I understand the MAF is not the problem therefore. Unplugging the MAF puts car in a backup/safe/default air/fuel ratio mode, at least that's what I have read. So unplugging the MAF just masks the real problem.

Starting to think the main computer is faulty or something..
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Old 07-18-2016, 12:27 PM   #11
daru
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Problem seems to have been solved. It was something with fuel pump. My guess is a not 100% air tight hose assembly between pump and pump holder/rack in fuel tank.

Can probably return the MAF I bought, we will see.

Well, this car has been very "educational". But learned a lot so got to see that as positive.

Thanks for everybody who commented!
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