1.9 tick over

[Mugs]

i have a 1997 1.9 auto Z3 and i seem to be having a slight problem at tickover that someone may be able to help with.
she runs fine but every now and again, when she is on tickover, she feels very lumpy, almost as if she's missing (judders and shakes but doesn't cut out).
sometimes, after a god run, she feels fine but other times she is lumpy. she is especially bad when she's been switched off for a while then restarted.
she has had new plugs, new air filter, MAF cleaned, new rad and coolant and an oil change if that makes a difference?
has anyone got any ideas what could be causing this?

[Del]

There should be a “support group” for M44 engine owners who experience this rough cold start issue. I was chasing the problem myself for 6 months (changed loads of things) before stumbling on the cause. A common cause for this seems to be dirt in the engine oil causing a slight build-up of gunge around the hydraulic valve lifters – causing them to stick to varying degrees. I suspect that some of the oil-ways around this area for the M44 engine are a bit narrow. I would suggest an oil change using something with a reputation for being nice and thin with an engine cleaning reputation e.g. Mobil 1 (0W-40). Use an engine flush only if you’re happy to do so (opinions differ). Also make sure you change all three o-rings on the oil filter as the two smaller ones have an influence on maintaining oil pressure in the upper engine – gets “overlooked” in garages.

BMW mechanics used to typically play around with the ignition timing on the M44 engine to “cure” this problem but I’m not convinced that this was the problem.

http://www.zroadster.net/forum/viewtopi ... aa#p365861

http://www.zroadster.net/forum/viewtopi ... hlight=m44

http://www.zroadster.net/forum/viewtopi ... 72#p340572

http://www.zroadster.net/forum/viewtopi ... 94#p343594

[DC]

I used STP Petrol Treatment to release a stuck fuel gauge sender (which it did immediately) and noticed a definite improvement in tick over, much smoother.
Would be worth a go as cheap and has others benefits.
You seem to have done most things that should help.
Cleaning the MAF has resulted in problems for a few folk.

[Mugs]

thanks for the replies.
she seems fine when cold - it seems to happen when she is warm and switched off for 1/2 hour or so. she never sounds like a steam engine either.
i did an AutoSolo with her yesterday and it seemed that every half-hour when i restarted her, i had the lumpy tickover but after a good run it seemed to disappear for a few minutes but then return.
i have used 5w40 in the last oil change (100 miles ago) but i will try a flush then use 0w40 and see if this helps.
it also seems that if i put my foot on the throttle and let it tick over at 800 - 1000rpm then it is ok.
i will try the petrol additive and a new fuel filter too.
i might try turning up the tickover - anyone know how this is done on the m44?

[Del]

The oil problem I mentioned is very specifically related to cold start situations and gets worse when the weather gets colder. If you are getting the problem on a hot engine, I agree that there may be another cause. It would be interesting to see if the ECU has stored any error codes e.g. with an OBD II code reader.

[Mugs]

ok, thanks.

i have an OBD 11 reader but where do i plug into on the zed? is it the round plug where the service reset tool fits or elsewhere?

[Del]

is it the round plug where the service reset tool fits

Yes - you may need an adapter cable (approx. £4 ebay)
As far as I am aware, the idle speed is controlled by the sensors and ECU so there is no little screw to turn as in the old days.

Are you happy you have no splits in rubber pipes causing vacuum leaks? As well as inspecting the pipes closely a rough & ready test is to disconnect the small rubber vacuum pipe at the front of the M44 engine. The idle speed should increase slightly as a deliberate vacuum leak is created. If there is no change in the idle speed, it may indicate a pre-existing leak elsewhere.

When the problem occurs, turn off the engine and restart with the MAF sensor disconnected - is the idle better with it disconnected and the ECU using a factory default setting - if so it may be the MAF sensor.

One final item that can be a bit tricky to tie down is a faulty crank case breather valve - they can either stick open causing an internal vacuum leak or stick shut and cause other running/performance issues.
http://www.ebay.co.uk/itm/BMW-Genuine-C ... 1e86b5cc51

[Mugs]

thanks Del, i'll have a look this week.

[Mugs]

i haven't got around to getting an adapter cable for my diagnostic kit yet but today i went to start my zed and she wouldn't tick over at all, she just kept cutting out.
so, i disconnected the MAF and she started and ran fine. i take it this means the MAF has gone?
i have also found the CAT is rattling away so i will need to get a new one.
could the CAT have caused the MAF to go or vice-versa?
also, is it ok to do a very short journey without the MAF connected (just to get the new cat fitted) or should i get the MAF sorted first?

[Del]

From my own DIY experience, when a car either starts or runs much better with the MAF sensor disconnected - then the MAF sensor itself is the likely problem. We had a family car (not the Z3) which was causing occasional starting problems and kept throwing lean error codes - I disconnected the MAF during one starting problem episode and it started up fine - changed the MAF and no further problems.

Cats can just get old and break up inside. However a longer-term engine "misfire" problem can also damage the cat. I am not aware that the cat can influence the MAF sensor.

As far as I am aware, it is ok to drive the car a short distance with the MAF sensor disconnected. Normally this would take the edge off performance as the ECU would be working from factory approximations - but in your case these approximations sound better than the faulty MAF.

[Mugs]

thanks Del.