Rough idle

[Johnoc70]

Hi. My X5 E53 is idling rough and I was getting lean run on both banks. . I found a small vacuum leak in the lower boot and replaced it. I thought that would fix it but when I started up the car it would idle fine for about 30 seconds then the revs would drop down to about 600rpm and idle roughly. I thought it may be the MAF sensor so bought a cheap MAF sensor off eBay, its still doing the same thing. Could it just be a cheap MAF is still causing the issue. As soon as I unplug the MAF sensor the car idles perfectly. Any help would be much appreciated

Thanks John.

[dmarkovina]

Engine?

[Johnoc70]

3.0i petrol

[dmarkovina]

With maf plugged in what are the petrol short term trim values?

[Johnoc70]

I don’t have those values. Can I get them with my C110 code scanner.

[dmarkovina]

Not sure - does it have a data stream option or anything of the sort? Have you tried cleaning the sensor? It is Indeed the most likely culprit if all is ok with it being unplugged.

[Johnoc70]

Hi it has data streaming so will have a look. MAF is brand new but a cheap one. Maybe worth investing in a good oem MAF

[d_a_n1979]

Johnoc70 said:

Hi. My X5 E53 is idling rough and I was getting lean run on both banks. . I found a small vacuum leak in the lower boot and replaced it. I thought that would fix it but when I started up the car it would idle fine for about 30 seconds then the revs would drop down to about 600rpm and idle roughly. I thought it may be the MAF sensor so bought a cheap MAF sensor off eBay, its still doing the same thing. Could it just be a cheap MAF is still causing the issue. As soon as I unplug the MAF sensor the car idles perfectly. Any help would be much appreciated

Thanks John.

These motors do not like cheap MAFs or cam/crank sensors, so OEM BMW every time for these... others you’ll be fine with aftermarket (Meyle etc)

Guessing this is the M54 motor, then check the air intake boot from the MAF to the throttle body, these can split, more so where the ribbed section is and let in air making the car idle poorly. Check all other vac pipes too for same issues.

How does the car idle with the MAF unplugged? If the same, it’d likely point to the issue not bein MAF related.

You need a good code reader, not sure what mobile phone you have, but I’d highly recommend Carly for BMW and it’s relevant adapter dongle. It’s on both iOS and Android, around £100 all in, but very much worthwhile, more so in situations like this

[RafflesNH]

d_a_n1979 said:

8<

How does the car idle with the MAF unplugged? If the same, it’d likely point to the issue not bein MAF related.

8<

The OP has already stated: "As soon as I unplug the MAF sensor the car idles perfectly."

[dmarkovina]

I installed INPA on an old laptop and with a cheap obd cable now have a proper BMW diagnostics tool.

Also when just a quick diagnosis is needed, I use a cheap Bluetooth obd dongle off eBay, with Free obd apps on Google Play - you can both read and reset errors, plus get real time data stream - including short and long term fuel trims.