MAF or Throttle body (or something else) ???

[imi7]

Hi,

I have an X5 4.6is (2003). Recently have been driving through some major sandstorms here in the Middle East, so had the air filters replaced about 4 weeks ago during a routine service.

The car has been a little weird over the last 24 hours. I was waiting for a friend in a mall and had AC running and slept a while - when I woke up I noticed the car had stalled and therefore was no longer started (I was waiting for around 2 hours).

Then today, I noticed that if you switch the AC OFF, then the car would stall from idle as the revs drop below 500rpm (usually they idle at 700 rpm without the AC on). But, once the AC is switched on, revs increase and car doesnt stall at all during idle. I tested the car (in a private car park) by driving the car without the AC on, and sure enough as the revs drop towards idle the car would stall and turn off !!

I decided to unhook the MAF sensor to eliminate this possible fault. It is a pain to remove and I was unsucessful. However, I did notice that if I had the car on IDLE and the AC switched off, tapping the MAF housing would cause the car to drop revs to a stall - this makes me think it's the MAF, but having had it replaced only 2.5 yrs ago from BMW seems a bit unusual.

Could it be anything else? Throttle body perhaps? I will try to clean the MAF as dont want to buy another new one for £300 from the stealer here. Also, what do you guys think of this one on ebay: -

Air Flow Mass Meter Sensor BMW X5 4.4i 4.6is (E53) 96-01 MAF | eBay

Look forward to hearing from you.

Cheers

Imi.

UK Expat living in the Middle East .

[bcredliner]

Is the new air filter one that is oiled from the supplier or perhaps a re-usable filter?

[SlickGT1]

Originally Posted by bcredliner

Is the new air filter one that is oiled from the supplier or perhaps a re-usable filter?

+1. Are your filter K&N, oil type?

Clean your TB, and your maf. Use CRC maf cleaner, and TB cleaner respectively.

Do you know how bad it is for your car, to idle it, with AC on, in desert heat for two hours? You guys must have really cheap fuel as well. lol.

[imi7]

Hi,

Thanks for the comments - I just had an oil change 4 weeks ago - used Magnatec standard rating. Also changed the air filter from a normal garage - he installed a standard BMW air filter (not sure it was oiled - is this important?).

I had no idea its bad for the AC to be on whilst idle - what are the consequences (wont be doing that again !). ITs been REALLY dusty here as doesnt help I have to drive through a sandstorm every 2 weeks for the last 2 months - guess it takes its toll.

Just realised have not changed the SP's for a long while - will also do that along with cleaning the MAF and TB. Any recommendations for SP's?

Yes gas is very cheap here - costs me about £9 to fill her up - loving it .

Cheers.

[bcredliner]

Very important to know what air filter. If it is an oiled filter they sometimes have too much oil on them and it blows through to contaminate the MAS. That will cause it to malfunction. Must be cleaned and still may not work,--may be history.

If you replace the MAS I would purchase original BMW replacement, not something to chance an inferior part.

[SlickGT1]

If it's original BMW filter, you should be fine.

Check realOEM.com for which plugs to get. Get OE if in doubt. Disconnect the harness from the maf. Should be fairly easy to do. See if it idles with it unplugged.

[imi7]

The air filter is not the oil one...just a standard OE one. I will test the MAF tomorrow and report back. If it's not the MAF, what else could it be?

[imi7]

I managed to disconnect the MAF sensor, and hey presto, the idle revs are fine - looks like the culprit is the MAF sensor on its way out. Here's whatI plan to do - do you think I should replace the MAF with a Bosch one or would cleaning suffice:-

- Clean MAF (should I really replace it and can anyone recommend a EU stockist??)
- Clean TB
- Replace all Spark Plugs with NGK Iridium IX's
- Maybe replace the Spark plug hoses??

Thanks for the advice.

Imi

Very Important - what kind of Screw driver do I need to remove the 2 MAF 'star' headed screws and are they easy to buy online?

[Isambard]

I bought a Pierburg sensor for £60 a few years back for my CLK. Just a straightforward 5 minute changeout and a fraction of the price. Worked a treat,, never had ANY problems. If my MAF sensor goes on my X I'll be buying from Pierburg again.

For the 'star' type screw I just used a standard tamperproof torx bit. Sorry, can't remember what size. However I do remember it not fitting that well, so I just carefully used pliers on the head of the screw. Its only screwed into the plastic so not tight-taking it out or putting it back in

[imi7]

Found a place in the UK that sells the exact Bosch MAF for a bargain price of £94 so decided to get it, instead of cleaning the old sensor (dealer price here for exactly the same part in Middle East is approx £280) . Also ordered NGK Iridium IX plugs, and will order valve cover gaskets just in case.

Car goes to the mechanic after 2 weeks - will keep you posted.

Thanks for all the advice.
Cheers.