Engine cutting out, low on power. *solved*

[z3steve]

Evening all. Ive just had a nightmare journey back from Cambridge - I got to the snarled up Dartford crossing and the car just died. Started up ok, but everytime I didnt give it any gas, it cut out. From then on it was really rough, almost misfiring all the time.

Ive had a quick search online and only came up with the idea of sensors being at fault.

Any input would be great.

BMW Z3 2.0 1999

Cheers, Steve

[aceman]

I bet it is your MAF try disconnecting it and see if it runs. The ecu drops into a safe mode and a EML light will come on the dash but it should run.

[z3steve]

What exactly does the MAF do?

Thanks for the reply Aceman, will check that out now.

[z3steve]

Well I disconnected the plug to the MAF and its still rough.

It did stay running though but not driven it (would that make a difference?)

Cheers, Steve

[aceman]

Mass Air Flow, measures the amount of air entering the engine. It will run a little rough with it disconnected but if it stops it cutting out it could be the culprit. Thing to do would be to get a diagnostic done send see if there there are any other errors pending as maf problems don't always throw up an error.

[z3steve]

Ah, thank you.

Will have to do a bit of research and see if theres anyone round here that can do the diagnostics.

Thanks for your help, I'll post what the culprit is if it ever gets found!

Cheers, Steve

[Del]

Many have reported a similar fault which turned out to be a camshaft position sensor. However, best to plug the car into a diagnostic fault finder. I have a local garage that only charges £20 + VAT for doing this. If you want to do it regularly, there are plenty of inexpensive fault code readers on ebay.

[z3steve]

Ok, got it plugged in and it came up with the following five codes:

P0173 Fuel trim malfunction (bank 2)
P0170 Fuel trim (bank 1) Malfunction
P0101 MAF or VAF sensor circuit range / performance problem
P0304 Cylinder 4 misfire detected
P0303 Cylinder 3 misfire detected

Help me!!!!!!!

So would you think this is a MAF problem that is highlighting the others?

Cheers,

Steve

[Robert T]

A malfunctioning MAF would likely cause misfueling when the engine is cold, which I guess could lead to the other errors being thrown. I think I would replace the MAF and see if the other errors go away - if not you have another problem as well. I think the explicit MAF error is enough to say that it is not working properly, but to be on the safe side, I would check the condition of the rubber hoses first, as an air leak could fool the ECU into thinking the MAF was duff. I'm not just sure how it determines the value is out of range, my guess is that it is a fixed range and that the MAF is duff, but if it is a dynamic range, then it could feasibly be an air leak. No sign of a camshaft sensor error though.

Cheers R.

[z3steve]

Thanks Robert.

I think replacing the MAF is going to be my first step. Ive checked the hoses and they are all sound, I replaced the main one with the small tube teeing off about 6 months ago so that should be fine.

Will post the results when I get it swapped.

Steve

[z3steve]

Ok so new MAF on today, I erased the codes and started it up. Its still running rough so I plug in the scanner again and it says misfire detected cylinders 1-3. The other MAF code problem has gone.

Should I be changing the plugs?

Regards, Steve

[Gazza]

The misfire reads 1-3, change one of those coilpacks onto No.4 and clear the codes. If it now reads 1,2,4, for example, you'll know it's a coilpack problem.

[Robert T]

Well it sounds like one problem is fixed! Seems odd that so many cylinders should report misfires - really need to know how it detects a misfire in order to identify the next most likely component - my current thoughts are along the lines of camshaft or crankshaft sensors - not dead, but throwing erratic values that cause the ECU to think it has a misfire. On an older car I would be suspecting the HT lead between the coil and the distributor, but I don't think the sixes even have HT leads do they? It is low voltage into the coilpack and the coilpack sits directly on the top of the sparkplug. Have you checked the condition of the plugs? If it has been running rich, then they could be sooted up?

Cheers R.

[z3steve]

Ive just taken it out for a run, and although it runs okay at speed the idle is still very erratic, it did cut out again actually. I plugged the scanner in but this time it comes up with no faults detected. I think ill do the plugs and go from there.

Cheers, Steve

[z3steve]

Replaced the plugs.

No change.......Plugged the scanner in and its come back with the fuel trim malfunction (banks 1 and 2) codes again. The exhaust smell very petrol like too.

I might have to take it to the garage, cant be doing with replacing everything like a lot of people - havent got the time.

Cheers, Steve

[BladeRunner919]

Steve, you need to get it on something that reads the BMW codes, not just the generic OBDII codes.

[z3steve]

Thanks for the replies. Its down at the garage hopefully being sorted as we speak. Will let you all know what the outcome is.

Cheers, Steve

[Gazza]

Fuel smell in the exhaust is unburnt fuel, I would think coilpacks would be likely.

[Del]

Sorry to hear your ongoing problem and trust your garage will sort it. Statistically, OBD codes 170 & 173 crop up commonly with either vacuum leaks for a MAF problem - an air filter choked with leaves would, for example, impact on the MAF. Would be very interested in the cause found.

[z3steve]

Evening all!

Got the car back today (been away for a week) and its purring again.

Turns out it was the 'cyclone valve' that was blocked, so it was replaced. What this part does I have no idea, he did tell me but it was double dutch to me!

Anyway all sorted thank god at a cost of £175.

Cheers for all the replies and I hope this thread will be of some help to others in the same boat.

Regards, Steve

[Del]

Hi Steve

Cylclone valve = aka crankcase ventilation valve.

that was a brain teaser that had us all foxed - glad you got it sorted

[z3steve]

Hi Del, yes I didn't even know such a thing existed but i'm no mechanic!

I must give a mention to Ken at Bavarian Autos in High Brooms near Tunbridge Wells. He knows what he's on about and a thoroughly nice chap to boot.

Regards, Steve

[Southernboy]

Don't suppose you could tell us where this beast is located, so if anyone else has a hassle, they can have a look at it??

[Del]

Southernboy - set of 3 videos for the 6 pot M54 engine on YouTube.
The 4 pot engines are a lot easier.

[Southernboy]

cheers

[bertiejaffa]

(Apologises for asking again) but Has anyone actually changes the crank ventilation valve? The 3 videos look very good but I suspect that it would take me a few days!

[Southernboy]

I have..... and it takes about 30 mins..... I changed the unit on my 2.8.

[bertiejaffa]

I have..... and it takes about 30 mins..... I changed the unit on my 2.8.

Any chance you can pop round

[Southernboy]

No problem buddy..... but the Bentleys manual describes the procedure very well.... Basically get everything out the way so you can get under the intake manifold..... Air filter box, MAF and related hoses, electrical wiring connectors to various items etc etc... best take all the big rubber hoses off all the way including the 90 deg boot...and the power steering reservoir which can simply be pushed aside once unbolted from it's mounting.... very simple really.

[bertiejaffa]

cheers pal, will have a look in that. The oil light on the 2.0l hardly comes on anymore, but it is the only remaining niggle that it has... everything else that I want to do to it is optional/cosmetic

[Southernboy]

That's a great place to be with a car.... everything is back to 100% bar the small issue. Sounds like you have a premium 2.0 there Lee - Congrats, I know you've been at it for a couple of years....