air mass meter defective?

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air mass meter defective?

Postby Willem » Fri Jul 16, 2010 7:07 pm

Hello all,

I have a problem with my BMW 318 '98. The engine runs very lean and has no performance at all.
When I do the snap throttle test the air-mass meter doesn't go above 3,5 Volt. Can I asume the air-mass meter is defective? Here's the waveform with lambda signal in red:
acceleratietest.gif


(Excuse my english I'm from Holland)
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Re: air mass meter defective?

Postby NigeC » Mon Jul 19, 2010 9:42 am

Hi Willem,

3.5v is very low but check you have no induction leaks too.

Regards,
Nige
Nigeiometric efficiency = 14 wrong : 1 right....
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Re: air mass meter defective?

Postby Willem » Mon Jul 19, 2010 12:23 pm

Hello Nige,

Thanks for your reply, as far as I can tell there are no vacuum leaks. I've checked it all. Tonight I will try to clean the air mass meter and see if there is any difference. You wil find the results in this topic tomorrow.

Willem.
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Re: air mass meter defective?

Postby Matt Fanslow » Mon Jul 19, 2010 8:43 pm

On that engine/system I would expect to see an initial "spike" of over 4.5 volts. This is assuming you are snapping it WOT like you don't own it. A quick look at fuel trims may also aid you in condemning the MAF.

HTH.

Later, Matt.
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Re: air mass meter defective?

Postby Willem » Tue Jul 20, 2010 6:19 pm

Hello Matt,

I did the trottle test WOT until the rpm limiter. I have cleaned the Air-Mass meter and the engine runs much better, but I'm still not happy with the second throttle test. As you can see the voltage is a little bit higher, although the lambda signal still shows lean. Shouldn't the lambda give rich during WOT?
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CleanAirmass.gif
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Re: air mass meter defective?

Postby Matt Fanslow » Tue Jul 20, 2010 8:37 pm

You shouldn't really need to hit the rev limiter. The initial gulp of air is going to be about as much air as the engine can ingest.

I would expect the Lambda sensor to reflect fuel being added.
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