Z4 Coupe sometimes stalls when put in reverse

[AveZ4coop]

Hi All

Got an odd issue here. Occasionally when I put the car in reverse after coming to a halt (with my foot still on the clutch) the engine stalls. It has given me a few heart stopping moments as I live on a busy road and have to reverse onto my drive.

It doesn't happen very often and initially I thought it was due to a maybe not coming to a complete halt. But it has now done it a couple of times when I am most definitely stopped and the clutch is fully pressed down. No other idling or transmission issues, so at a bit of a loss?

Any one got any ideas???

 

[wonkydonkey]

Is it hard (harder than usual :lol to select reverse gear in these instances when it stalls? And does the car try to lurch backwards as it goes into gear when it stalls? If so, your clutch may need bleeding.

 

[AveZ4coop]

It doesn't seem any more difficult to select reverse. Doesn't seem to lurch either. Is totally baffling and only occurs occasionally. :?

 

[wonkydonkey]

Hmm...definitely a bit of a head scratcher, and it feels like it might be some weird coincidental issue that appears to tie in with the selection of reverse, somehow?? I'll mull it over subconsciously!

 

[AveZ4coop]

Any Mulling greatly appreciated!!

 

[tee.gilding]

Have you checked MAF? Might be coincidental the reverse bit, so worth checking your MAF and checking for any air leaks in the air intake. My old E46 used to do this occasionally under very similar conditions, but generally when moving forward. I replaced the MAF and intake and sorted the issue.

 

[ph001]

I guess the only difference with reverse is lack of sychromesh so any clutch issues will be highlighted, but if you say it goes in smoothly with no dragging doesn't sound like it's the culprit. The reverse lights do come on of course so maybe some kind of grounding issue there could be upsetting the electrics? Suppose you could pull the fuse on the reverse light and run it for a few days to see if it makes any difference. Just try not to do much reversing in public!

 

[AveZ4coop]

Update: Now does it when stopped with clutch down and no gear selected.

Have you checked MAF? Might be coincidental the reverse bit, so worth checking your MAF and checking for any air leaks in the air intake. My old E46 used to do this occasionally under very similar conditions, but generally when moving forward. I replaced the MAF and intake and sorted the issue.

Your original diagnosis may have been correct? Will have to have an investigation as soon as time allows.