Engine Light? No change in performance/drive?

S

sixspeed

Senior member
 Surrey, UK
Well this could scupper my plans to make the NE meet this weekend! ...

Just had the yellow "engine-block" light come on. No apparent change in the way the car drives, no loss of performance, lumpy running etc. It did come on once before, then went out within 50 miles or so. That was a while back, and I put it down to dodgy fuel or such like. It's been in for a service since and no error codes came up.

I will have to drive the car home later and maybe it will go out again. A quick google suggests abnormal emissions could be a cause of this. Just wondering if it's a possible lambda issue? Did those that have experience lambda problems have this light appear? Any other symptoms?

Hoping it clears - but if its still on after a short drive this evening and I can't get a dealer to scan it tomorrow, I might not make the drive on Sunday... :(
 
gaurantee its a lambda sensor, in a few cases the cars seem to run better once its failed!!
 
I agree,I had a post CAT lambda fail and mine definitely had more upper end urge but I remember thinking that lower down the rev range was a little flat, it`s all subjective though.

I was told by BMW that it was ok to drive for a limited period with the light on so took their advice only for the car to default to limp home mode on New Years Eve!
 
Same as me mate, it's probably the O2/lambda sensors.

The CEL turned on but the car ran fine so i took it to the dealer. He told me it's a common fault (the sensors) and that it would run fine nonetheless. Then the CEL turned itself off for a week or so before it came permanently on and the car still ran fine. After 1-2 months though it started running rough and too rich. Unburnt petrol was coming out the back and it became very hard to drive smoothly. It kept stuttering and surging at lower revs but higher up it was OK. I didnt use the car for a couple of weeks until i had a set of new sensors imported here and then i had them all swapped. The car ran like a beauty immediately after it got its new sensors.
 
Didnt you just clean out your Gruppe M too? I've had 2 go, sometimes runs better as it's richer than usual.
 
I did... need to check the MAF incase theres been any excess oil contamination. However that did happen the first time I cleaned it, and it ran like crap!

I did just fill up with a new tank of petrol about 10 miles previous to it coming on, and I've read a couple of comments about the CEL lighting up on E46 M3s due to the petrol filler cap not sealing correctly (?!).

My instinct is O2/Lamda sensor though, hence the post, but just wanted to confirm symptoms from others.
 
Mine's also come on due to crap fuel, which made it misfire for 300yds, but then it corrected it again and the light went off.

MAF light will stay on and you should feel it richer usually.

To be honest to get to your mileage without having one go is either great luck or testiment to the gruppe m hiding it better than the standard airbox.

whats 5% less economy when ur about to do 700 miles ? lol
 
Well I've gone over the car this morning. MAF is oil-free so it's not the cleaned/reoiled K&N that is at fault. Light is still on at the moment, but I can't feel any detrimental effects when driving, so I'm going to go for it and come up for the NE meet I think! I'll get it into the dealer next week.
 
My emission light came on last night as well(again), however, i have 100 cell cats so maybe that has something to do with it.

Mine had to go into the garage a few weeks back to replace bank one of the manifold as one of the oxygen sensors come loose from the manifold. The technician at BMW said he'd never come across something like it as the sensor is welded into a slot on the manifold so shouldn't come loose. I hope your not in the early stages of something similar...

You may want to get the car onto a ramp and check for any exhaust fume leaks...
 
I think there are a number of things this could be. On my other BMW (3 Series E46) the light came on due to a cam shaft sensor failure. It was a very cheap fix if I recall correctly. The indy I use said it was OK to drive while I waited for the part to come in although he said it might reduce the mpg a bit.
 
Well I started the car earlier just as I was about to make a move for the North, and it started idling a bit erratically and hunting for revs... exhaust was smelling pretty rich, so as far as the meet goes tomorrow I've decided it's best not to be breaking down a few hundred miles from home and putting miles on the car if it's not running right.

It's since calmed down again and seems ok, but not worth the risk when it's a 600 mile round trip. Ho hum! Next time!
 
This happened on my old 2.5, turned out it was a bad plug, intermitently missing causing the light to come on and off and then missed and ran a bit lumpy like you described... quick fix
 
That sounds like a fair analysis given the symptoms. Sure it'll be something simple, just a shame I can't get it dealt with before tomorrow.
 
worth taking out the plugs or checking the leads at both ends (if you have the required degree in meta physics that you probably need to take the engine cover off - not tried on my M... hoping not to have to !) :D
 
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