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Old 07-30-2019, 09:36 AM   #1
foxbass
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Join Date: Aug 2015
Location: North London
Posts: 17
My Ride: e46 1.8i touring
Air mass meter. Clean? Replace?

Hi all.
Firstly, my new ride is the 318i touring 04, face lift with 67 thou. This has the later engine with coils on each plug.

My mechanic has read the cpu and identified a fault with the AMM. The symptom is low idle speed when cold and a flat spot under acceleration with a surge around 3000rpm. It is subtle but results in reduced economy.

He suggested I try cleaning it first with carb cleaner before considering a new meter. (It had stood for a while at the dealer)

Then to throw it open to this forum to ask which is the best aftermarket AMM.

OEM units are expensive so while I go out to the garage with a can o spray, any suggestions?
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Old 07-30-2019, 09:59 AM   #2
DEADF15H
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Join Date: Jul 2012
Location: Boca Raton, FL or Salisbury, NC
Posts: 2,176
My Ride: 2001 325i Auto
Model: 325i
Transmission: Auto
Get the correct part number from realoem.com. Use a Siemens/VDO, they make them for BMW, but your's won't have the logo.
I haven't seen cleaning it work yet, but you may be the first. You can install it yourself in 30 minutes. Check YouTube. Easy Peezy.

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Old 07-30-2019, 07:56 PM   #3
ewcmr2
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Use a product made for airflow meters, not carb cleaner.
I've had success with this, if it's doesnt help you're not out much $$.
https://www.amazon.com/CRC-05110-Mas...SIN=B000J19XSA
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Old 08-02-2019, 03:34 AM   #4
foxbass
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Join Date: Aug 2015
Location: North London
Posts: 17
My Ride: e46 1.8i touring
Thanks guys!
I got out my tool kit and took out the air box (a weird design on UK models. You have to turn it upside down to unscrew the lid) to find the MAF actually holds the air filter in place. Took the MAF off the duct that links to the throttle body and found the problem. Some goon had not paid attention to the seating of the large flat rubber band which had subsequently folded over and got torn slightly. As it was just about salvageable, I re-positioned it, applied some lube and pushed it back together right. It had been sucking air down-wind of the MAF so the engine was running lean, hence the flat spot and inability to balance throttle and clutch nicely. (after 750,000 miles, reckon I should've got that down!) It was just one of several things that had not been assembled right by some service monkey!
Mech bloke was right though. He said the throttle body would be pretty dirty and to give it a dousing in cleaner, wipe it out (by pushing open the butterfly) then soak it again and take it for a blast up the road.
Result?
The car behaves perfectly. Joy!
Total cost = one can of cleaner and a few beers for the mech.
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Old 08-02-2019, 03:37 AM   #5
foxbass
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Join Date: Aug 2015
Location: North London
Posts: 17
My Ride: e46 1.8i touring
Oh yeah. Story's not quite done yet. He cleared the fault code and said to bring it back after a few days to check the MAF again. Er... 3 beers!
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Old 08-02-2019, 08:01 AM   #6
DEADF15H
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Join Date: Jul 2012
Location: Boca Raton, FL or Salisbury, NC
Posts: 2,176
My Ride: 2001 325i Auto
Model: 325i
Transmission: Auto
Time to spend >$30 and get yourself a OBD II Bluetooth connector and OBD Fusion so you can get or clear the coded yourself.
Congrats on the fix!

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Last edited by DEADF15H; 08-02-2019 at 08:05 AM.
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Old 08-02-2019, 09:12 PM   #7
Filmy
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Join Date: Jul 2018
Location: Valley Village, CA
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My Ride: 02 325iT
Year: 2002
Model: 325i Touring
Transmission: Auto
Glad the mechanic's fix worked for you, but a word of caution: it is highly recommended that you do not open the butterfly of the throttle body manually. I forget why now, but I've read that in more than a few write-ups. Maybe it's a different thing with a 318i TB than with M54 engines, but probably the same reason(s) why to not do it. Do with this information what you like - I'm just putting it out there.
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