Problems with idle and shuddering. Please help!

[outrun]

Hey all

My M has decided to stick at around 1300 rpm when idling and then drop down to normal and then go back up again and so on. It also shudders a little when i'm driving at a constant speed.

BMW put it on diagnostics and it showed nothing but I took their engineer for a spin and he witnessed the fault.

He suggested changing the accelerator switch (whatever that is) which I did for the princly sum of £110. It worked for about a week and now the problem is back.

Any ideas?

I was thinking it may be a fuel issue but I always use Optimax so it shouldn't be. I let it run down to below a quarter of a tank and then tried some Esso super unleaded but it has made no difference.

Please help guys.

[Greenbat]

Are you covered under warranty?

If you are not then I suggest you do not change things under trial and error but to actually try and plug in the diagnostics equipment when the fault is actually happening. I know with intermittent faults this is difficult but in the long run might save you some money.

Saying that I had a similar problem on an E36 M3 and it turned out to be the one of the oxygen sensors. This was after I had changed the coils and a mutlitude of sensors.

Cheers

Greenbat

[David1975]

Hi Outrun,

Congrats on the new MC. I am anew owner (s50) too and mine does the very same thing. It feels like you are running out of petrol and then picks up again. Mine usually does it when sat about 30-40 in 4th or 5th with little trottle. Drives me mad. Got mine into an indy on Friday for other stuff so will ask him to have a look. I'll let you know the outcome. Does yours seem to bog down when using the gearing to slow down (taking foot off the gas) when the aircon is on. I have noticed mine doing that too.

Does yours also rev very high when you are starting from cold. Mine does and i have to blip the throttle and this usually solves the problem. I have a feeling all these problems are related.


Good luck

DAve

[outrun]

Thanks for the replies guys.

Please keep me in touch with your outcome David.

I've been advised that it could be some vacuum hoses that connect into the air filter box. I'm told
these suffer from splits and give air flow issues.

I'll get it checked inthe next week or two and post the outcome.

Cheers

[SteveB]

Had a simular problem a few weeks ago
If you look down the list to High revs when starting
The vacumn hose under the inlet manifold and the blanking piece had split
I had to remove the 90 degree pipe that connects the air filter box to the inlet manifold
Down next to the dipstick tube is a vacumn pipe that goes into a Y piece one side goes to a valve the other has a blanking piece
The vacumn tube and the blanking piece were both split
Cost about £3.00 at local accessory store for some tube and a blanking piece
Starts as normal and is smooth on constant runnig now.

[exdos]

I wonder if some of these intermittent problems might relate to contamination of the MAF :?:

I found this useful link about cleaning the MAF: http://www.louv.tv/cars/m5/MAF/

[outrun]

Cheers for the help again. I'm off to Northern Ireland on the Ferry with wife and dog (and BMW roof rails with carrier - looks well smart) on Friday. I'm intending on trying the fix with the vacuum pipes first next week. I'll post the results when I have done it.

[4motion]

POSSIBLY A FAULT WITH THE IDLE REGULATING VALVE PART # 13411733090 :(

[Ivo]

Too bad the old posts are gone, I wrote some posts about this.

In short: idle control potmeter / vanos valve / DME is what they replaced in my case :roll:

[David1975]

Hi Outrun,

have you had any closure on your idling problem?

cheers

David

[KIDDLE]

Just had mine fixed under EW ... was the MAF, changed it on the car (S54) and now she is perfect !

[Brett]

Hi Outrun,

have you had any closure on your idling problem?

cheers

David

Nope - he has sold the car to me and I have now experienced it first hand.

Drove to the airport on Tuesday morning - car started at "normal" revs at home. Pulled into the car park where the revs stuck at about 1300 rpm. Blipped the throttle, but no joy. Didn't have time to try work it out, so turned off and got my flight. Got back last night, turned the key - revs shot up to 1600 initially, blipped the throttle and they settled to around 1300 again. Left for home. Got the the queues at the Forth Road Bridge and "normal" idling had resumed.

I've not had a chance to look under the bonnet yet, but I am wondering whether a "sticking" throttle cable might be the cause? I don't know what the throttle mechanism is on the S50, but I had a similar problem on an old Corvette that I used to have and that turned out to be the cause.

Any thoughts anyone?

[Brett]

Hmmm....I know I am probably clutching at straws here but last two tankfuls have been V Power (or whatever Optimax is called now) and problem is worse than ever. Prior to that, I've been using BP's Ultimate unleaded and things were fine on the whole. Will switch back when I next need to fill the tank and will report back. Very smooth under acceleration but lumpy/irregular idling :?:

[biggusladdus]

Is it just a problem at idle?

I had a similar sounding problem with my e36 328. When I changed gear and released the throttle, the revs would stay up where they were for a while, and when they did fall, it was all of a sudden with a bit of a 'jerk'. The revs sometimes climbed up by themselves when I was sitting in traffic.

I took the car to an indy to have a diagnostics check done, and it was the potentiometer. Changed this and it has been fine ever since.

Total bill including the diagnostics check was less than half thanexcess would be for an extended warranty claim.

[Brett]

Is it just a problem at idle?

I had a similar sounding problem with my e36 328. When I changed gear and released the throttle, the revs would stay up where they were for a while, and when they did fall, it was all of a sudden with a bit of a 'jerk'. The revs sometimes climbed up by themselves when I was sitting in traffic.

I took the car to an indy to have a diagnostics check done, and it was the potentiometer. Changed this and it has been fine ever since.

Total bill including the diagnostics check was less than half thanexcess would be for an extended warranty claim.

Yeah the problem only appears at idle and is pretty much as described at the top of this message. Outrun did have the potentiometer replaced but the issue appears to have returned. I'll have to get it back in for a check and see what they come up with.

[Brett]

I took the car into BMW to have a look at - they test drove the car and witnessed the high idling. They suggested they would need to bring it in for diagnostics and that might take up to three days to complete. I couldn't spare the car over the past couple of weeks, so it hasn't been in.

What I did do, however, was read the manual and note that it recommended 95RON fuel for M powered Coupes. So the last three tanks have been 95RON rather than Optimax or V Power and the idle problem and shuddering has completely disappeared. I've done a good 500 miles without incident in all kinds of weather barring snow/ice but give it a month... :lol:

[David1975]

Brett, Glad to hear its solved the problem but my manual and sticker on fuel gauage recomemnds 98 Ron Fuel for my S50??

Was it the owners manual you were reading?

cheers

Dave

[BEN]

.............Was it the owners manual you were reading?

cheers

Dave

maybe one off an old sierra! :lol:

[Brett]

.............Was it the owners manual you were reading?

cheers

Dave

maybe one off an old sierra! :lol:

I'll double check but it was the owners manual that came with the car! I'm sure it said BMW on the outside rather than Sierra, but having worked the weekend from hell, I could be mistaken :shock:

[Brett]

Well I double checked today - the manual definitely says "BMW Z3" on the front. On page 26 under fuel grade it says 91RON for 2.8 and 3.0 engines and M engines 95RON. I also looked in the fuel filler cap and it says 95-98RON.

[Chris H]

That's weird. I too have a sticker on my fuel guage saying 98 RON. :?

[Brett]

I guess the acid test (for my car) will be to fill with 98RON when I get to the end of this tank and see whether I get the problem back. No sticker on my fuel gauge.

[exdos]

If it helps, according to the Owner's Handbook for the S54 MC/MR, it states:

The engine of your BMW is designed to run on Super Plus/premium plus petrol (octane number 98RON) Run the engine on this petrol by preference, in order to achieve rated performance and fuel consumption.
You can also run the engine on Premium-grade unleaded petrol (octane number 95RON) this is the minimum approved grade of petrol.

Would the S50 be any different :?:

[Brett]

No idea if the manual was updated/changed for the S54. I'll be getting mine out the car and having a good look again later...

[David1975]

Exdos,Brett:

My manual says exactly the same and mine is an S50.

Hope this helps

David

[c_w]

The sticker on my fuel gauge says 98RON, not sure about the book but I think for best performance 98RON is going to be best bet.

[Brett]

The sticker on my fuel gauge says 98RON, not sure about the book but I think for best performance 98RON is going to be best bet.

Weird - will have to check this out. I know my car was built Nov 99 and was a demonstrator at one of the BMW garages in Edinburgh, so there shouldn't be any wierd things there....still, the car is running great at the moment...next test, more 98RON I guess :?