2003 Z4 2.2i (M54) with intermittent split-second engine cut... and no codes!

[Consumer974]

Hi all,

My 2003 Z4 2.2 has developed an intermittent hiccup where the engine seems to cut out for a split second, then immediately comes back and carries on normally.

It usually seems to happen around 2–3k rpm, but not exclusively — it very occasionally does it higher up the rev range too. The best way I can describe it is a very brief engine cut for maybe half a second. When it does it, the yellow engine light & EML flashes up briefly at the same time, then disappears again and the engine resumes ticking over as normal.

Other than that, the car runs absolutely fine:

• starts fine
• idles fine
• pulls well
• no rough running or misfire
• no warning lights staying on afterwards

It’s also very intermittent. Sometimes it won’t do it at all on a 15–20 minute commute, other times it might do it once or even twice. I recently took it for an hour-long blast, getting it fully warmed-up then using the whole rev range and it behaved perfectly, leaving me suspecting it just needed an Italian tune-up... until five minutes from home it cut out briefly again

So far I’ve:

• scanned it with a generic OBD reader – no codes
• scanned it with INPA – no fault codes
• cleaned the idle control valve (was somewhat clogged), checked DISA valve (all operating fine)
• cleaned a few accessible intake/electrical connections while I was in there

Car’s just over 100k miles, had an oil change a couple of months ago, and the spark plugs were done within the last ~10k miles.

Has anyone else had this, especially with no fault codes being stored? I’m trying to work out the most likely culprits before I just start throwing parts at it.

Thanks in advance for any ideas.

 

[Zedebee]

Check the battery terminals are tight.

 

[Pondy]

Check the battery terminals are tight.

And fuel pump. Could be failing.