Engine light is on :(

[EdButler]

BMW confirms that it is NOT:
- the lambda probes as this would have no impact on performance or driveability.
- the cam sensor or TDC crank sensor as these would throw up specific fault codes.

Wrong!
and
Wrong!

Bloody dealerships... :roll:

1. Faulty Lambdas mean the mixture is incorrect, which most definitely would affect performance and drivability. When faulty, they nearly always make the car run RICH though, which shouldn't be your problem (still a possibility though!).
2. Every Crank/Cam sensor issue i've ever seen has not thrown a code. The sensor just 'thinks' its somewhere its not, usually causing the car to stall. I would rarely see misfires/lean codes from it though.

Running lean does sound like it could be a fuelling issue, or maybe even a vacuum leak of some kind. Maybe worth checking the EGR too... How does the car idle when hot and cold?

As said, you definitely SHOULD NOT drive a Lean running car for prolonged periods.

 

[alexwagner]

Well, I'm back from 500 miles over the weekend, with a new air flow meter : no change.

Car was great all the time except:
- after one hour on the motorway, it suddenly did the major coughing and spluttering, unable to maintain 70mph, very very rough, like it was running on only 2 cyls. At the same time, the yellow check engine light came on. I pulled over, cut the ignition, waited only 5 secs, restarted, and all was fine (even the yellow light went off) for the rest of that drive... weird.
- during a whole 1 or 2 minutes on a B-road, the car had minor misfiring. Went away on its own.
- had a handful of occurences of sudden drop of power during the start of overtaking manoeuvres

These were the only symptoms during about 10 hours of driving, so it is hard to reproduce at will, making diagnosis difficult.

Car is going in tomorow for a change of fuel pump and filter, together with the injector wiring loom.

Will keep you posted!

 

[EdButler]

I really hope they sort it for you, please report any findings back. It does seem quite dangerous! Is there any pattern to how it occurs? Overtaking would be 75%+ throttle at a guess... Do you know how you were driving the other times?

My money is still on an Intake Manifold air leak. They should smoke test it. My VX220 exhibited very similar symptoms also, with random hickups (usually with a 2' flame out of the exhaust immediately after!)

Also if you find yourself in that situation on the motorway again, you could always try dipping the clutch, ignition off, ingition on and bump start. Should reset the ECU without the peril of having of limping across lanes!

 

[grampian jock]

My ex demo Z4 engine light came on the very first day I got it. It had only done 2700miles. Main dealer had to order a replacement lambda sensor which took a week. Said running it would not do any harm. I did not really notice any performance problem but was taking it easy.

 

[chrismann85]

IIRC, it should come up with a history of the fault codes including when they came on and how far you have driven under the fault code.

EDIT: sorry didn't read the second page

Have you tried taking it to a different dealership?

 

[frazell]

Faulty lambda probes certainly do have an effect on performance. I recently had bank 1-3 pre-cat probe go and whilst the car ran 'OK' for a few days, after a week is was stuttering in low gears, very hesitant and in some cases felt like it was running on 3 cylinders.

I brought the sensor from BMW and fitted it myself, not too difficult to do if you have a couple of tools to do the job.

 

[alexwagner]

Faulty lambda probes certainly do have an effect on performance. I recently had bank 1-3 pre-cat probe go and whilst the car ran 'OK' for a few days, after a week is was stuttering in low gears, very hesitant and in some cases felt like it was running on 3 cylinders.

I brought the sensor from BMW and fitted it myself, not too difficult to do if you have a couple of tools to do the job.

Interesting. Sounds like my symptoms, but here's the thing:

The fault code readouts show lean mixture and misfiring on all 6 of the cylinders.
To BMW & I, this rules out lambda probes, because I would have to have 2 faultly lambda probes. Too unlikely.

BMW has checked for air leaks in the inlet manifold ; there are none. Besides, this would not be fixed by pulling over, cutting and restarting the engine...

BMW has also ruled out the EGR valve.

Possible causes remain:
- intermitent fuel pump electrical issue
- fuel pressure regulator electrical issue
- faulty ECU

They have called other dealerships, who are also puzzled.

They issued a case report today to Munich to get some info, as they are stuck. :-/

 

[Wondermike]

The fault code readouts show lean mixture and misfiring on all 6 of the cylinders.
To BMW & I, this rules out lambda probes, because I would have to have 2 faultly lambda probes. Too unlikely.

No expert, but at the rate these fail I would say 2 at once is a distinct possibility.

 

[alexwagner]

I have just posted a video of friday ; the motorway incident where it was suddenly very very rough indeed until I pulled over and started the engine again:

http://www.youtube.com/watch?v=22u4HU53z6c

(comments are in French, my other language)

 

[Wondermike]

Wow that sounds terrible, if my food blender sounded like that I'd be getting another one. That must be doing the engine some damage, no?

 

[alexwagner]

Wow that sounds terrible, if my food blender sounded like that I'd be getting another one. That must be doing the engine some damage, no?

I only let it run like that for 2 minutes, for the video. It was vibrating, but won't have done any harm.

 

[Andy]

wow... that ticking sounds terrible.. have you shown this to the dealer ?

ive had a few engine lights and a few splutters, if mine ever sounded like that id have the engine straight off..

i once had an alfa twinspark that made a noise a bit like that, & it expired a few miles later.

having said that, it does sound perfect after you restart it..

 

[alexwagner]

wow... that ticking sounds terrible.. have you shown this to the dealer ?

ive had a few engine lights and a few splutters, if mine ever sounded like that id have the engine straight off..

i once had an alfa twinspark that made a noise a bit like that, & it expired a few miles later.

having said that, it does sound perfect after you restart it..

I've sent the link to the dealer. I'll let you know what he thinks...

The engine's not going to expire ; it just sounds like it isn't getting any fuel. And this episode only lasted 2 minutes, in 10 hours of driving last weekend. Rest of the time, the engine is fabulous.

 

[EdButler]

wow... that ticking sounds terrible..

I think thats just the camera shaking.

Actually sounds like the car is running on 3 cylinders to me. Is there a hissing noise when it does this?

 

[alexwagner]

wow... that ticking sounds terrible..

I think thats just the camera shaking.

Actually sounds like the car is running on 3 cylinders to me. Is there a hissing noise when it does this?

The ticking sound is the engine ; the camera is in my hand, so no ticking sound from it.

Sounds like 3 cyls to me too. No hissing noise, no.

 

[EdButler]

Sorry my bad, looked like it was hitting the steering wheel.

Well if it is on a bank of 3 (which it certainly sounds like, after owning a beast of a 3cylinder car ), that basically narrows it down to the Lambda sensor of the failing bank! You can usually see this by scanning the ECU or removing the spark plugs to see if they are sooty and fouled.

 

[alexwagner]

Sorry my bad, looked like it was hitting the steering wheel.

Well if it is on a bank of 3 (which it certainly sounds like, after owning a beast of a 3cylinder car ), that basically narrows it down to the Lambda sensor of the failing bank! You can usually see this by scanning the ECU or removing the spark plugs to see if they are sooty and fouled.

The problem is:
- the fault codes indicate lean mixture on all 6 cyls (though not necessarily all 6 at once), which rules out a lambda probe
- just because it is running on 3 doesn't mean it is a bank of 3... it might be a mix
- also, everyone here is adament that lambda probes cause no subjective symptoms (if anything, performance is better without them!)

I'll have them inspect the plugs though...

 

[Andy]

both my lambda faults seemed to cause it to run rich, performance was affected, but nothing like yours.

id be moving to another dealer if they still cant see anything soon.

 

[frazell]

Like i said previously, the lambda failures on my car certainly did effect the cars performance, to its detriment.

They are very prone to failing so I wouldn't necessary rule out both going at once as the other poster said. Having said all that all my lambda failures came up as fault code on the scanner so it was pretty clear what was wrong.

I think (just my opinion) you should take it to another dealer. Hope you sort it out.

 

[alexwagner]

UPDATE:

My car is now cured (I've done 500 miles with no symptoms).

To cure the car, BMW changed the low pressure immersed fuel pump and the fuel filter.