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Joined: 23-April-2004
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Direct Link To This Post Topic: Losing Power
    Posted: 20-February-2006 at 04:13

Anyone know what could be wrong

Every now and again while driving along I seem to lose power in my car. When I put my foot on the throtle there is very little response from the engine..

This morning while stopped in traffic the engine cut out altogether but started again immediately.

 

Any ideas?

 

Thanks

 

Brian

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Direct Link To This Post Posted: 20-February-2006 at 04:25
what car you got???

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Direct Link To This Post Posted: 20-February-2006 at 04:27
could be a host of things! but sounds generally speaking like a fueling problem.

What car exactly is it?
Has it been serviced recently?

My suspicion would edge toward (ordered cheap to expensive):
- dirty throttle body(ies)
- Lamda sensor
- air flow meter

but then it could be something simple like a fuel filter!

If its a modern car get it to a dealer to diagnose on the computers. If older go to a beamer specialist or DIY.

Paul
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Direct Link To This Post Posted: 20-February-2006 at 04:50
Wrong gear? 
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Direct Link To This Post Posted: 20-February-2006 at 05:00

It's a 1997 520i..

It was serviced 3,000 miles ago.

Now if it was my wife driving i'd probably agree with KIN.....

Brian...
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Direct Link To This Post Posted: 20-February-2006 at 06:16

Brian - it sounds like a problem I had with an air mass flow sensor (or something that sounds like that!) last year on my e39.  The bad news is that if it is, it cost me about €500 to get sorted!  (I had to get it replaced)

It should show up on a diagnostic report - could be the cheapest way to verify.

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Direct Link To This Post Posted: 20-February-2006 at 06:19
Tell me if you need MAFs, a guy on the M5 Board sells the sensors by themselves rather than replacing the whole enclosure. I think all E39s use the same MAFs.

Costs less than €100 if you only need one.
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Direct Link To This Post Posted: 20-February-2006 at 06:21
Oh yeah... here is a way to test your MAFs. What BMW do you have?

http://www.e39m5.com/e39m5OBCtest.html
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Direct Link To This Post Posted: 20-February-2006 at 07:20

Would this MAF affect my fuel comsumption as I have noticed a drop.

Am I doing any damage by driving the car as it is?

Kin, it's 1997 E39...

if it is the MAF, can an ordinary mechanic do the job or does it have to be a main dealer

thanks for your help

 

Brian

 

 

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Direct Link To This Post Posted: 20-February-2006 at 07:23
@Kin: interesting reading that site!

@Jumbo: a "bad" MAF will usually cause over-fuel by design, as under-fuelling would be way more damaging to the engine. But long term over-fuelling will kill the catalytic convertor.
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Direct Link To This Post Posted: 20-February-2006 at 07:31
It is easy to do and you can change it yourself.

Bad MAFs are usually dirty MAFs caused by contaminants. This means the reading of airflow is wrong and usually less than what you are getting into the car. This causes the engine to pump less fuel in as it thinks there is less air. This is what causes the loss in power.

That is my take on it anyway...
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Direct Link To This Post Posted: 20-February-2006 at 07:44

Can I see the maf from looking into the engine?

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Direct Link To This Post Posted: 20-February-2006 at 08:09
I have marked the left one in my engine.


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Direct Link To This Post Posted: 20-February-2006 at 08:39
Thanks
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Direct Link To This Post Posted: 22-February-2006 at 17:11
I'd check the HT leads...it just takes a loose one to deliver the symptoms your experiencing.
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Direct Link To This Post Posted: 22-February-2006 at 18:01
I was loosing power on my 1996 323i from a failing / disintegrating cat after 9 years of use. However, unlike yourself, the car consistently felt like having 50% power up to cat replacement, rather than the "now and again" power dips you see. Although, when the cat was hot after a few miles driving the power drop was a little worse again.

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Direct Link To This Post Posted: 23-February-2006 at 04:34
Originally posted by ivanovoitch ivanovoitch wrote:

I'd check the HT leads...it just takes a loose one to deliver the symptoms your experiencing.

The E39 doesn't have HT leads - it uses individual coils
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Where did all the white water come from?

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Direct Link To This Post Posted: 23-February-2006 at 17:22
Yup...had mine replaced two days ago..all four. However alan in AC mentioned that one of the leads was loose which was contributing to my intermittent flat spot which is very similar to the problem described.

The leads effectively perform the same function as a HT so I described it as that...   
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