Rough Idle at startup...sometimes
 

Hello! Bought a second hand 2010 X5 30d with 120K kms, car runs great and very happy with it, love it actually.

Most mornings I get a rough idle when starting the car. The car starts, revs up to 1K, after a couple of seconds the revs lower and the roughness starts, goes on for about 10 secs and then the car runs fine. No lack of power, no smoke, no smell, no engine light no error codes. Never does it when warm or after sitting for a couple of hours, only when starting completely cold. Sleeps in garaje so low temperature is not an issue.

Took it to an indy and found a fault on glowplug 5, changed all plugs but still getting the rough idle. Doesnt happen every morning. ´The car isthere right now and (of course) he cant replicate the problem...

Any idea what it could be?

no one?

Sounds very much like a dead glow plug or two. Not uncommon and certainly not something that's immediately problematic although in cold climates during the colder months it will effect the initial idle and be difficult to start (within reason). Personally my engine has two faulty glow plugs, cylinders 1 and 5. I've yet to swap them out because living in South Africa and parking the car in a closed garage the climate never gets close to anything approaching cold. Still, it's gonna bite me in the arse one day soon no doubt.
Of c ouse I'm making assumptions here and your vehicle may be suffering from something unrelated but I would suggest getting it diagnosed before making any final judgments.

I had all six glow plugs replaced thinking it had something to do with that but still no luck. The car is at an indy dealer and hasn't done it for them for the four days it's been in there, no error codes either. I guess I'll have to take it to the dealer to get it diagnosed... was trying to avoid since the second hand warrantee only covers certain indys.

I've also been thinking might be a faulty/clogged injector, but I would imagine that I would notice a loss of power when driving. I've been thinking of adding an injector cleaner to see if it helps, anyone has had any luck with those?

Dont want to go crazy changing things either, already paid 400€ for the glow plugs...

Did they replace the glow plug controller at the same time?

On occasional cold starts you get 10 seconds of rough idle...and you've spend 400€ and want to chase this more????

Im not sure a BMW dealer will diagnose this any better than an indy- they tend to be the 'whats the code, we'll do what the computer tells us' variety.

Gas cars had idle air control valves that operate during cold start- when they get fouled, you can get that kind of behavior.. I am not that familiar with BMW diesels, lets see if someone chimes in.

Oh, smokey has a good question.....

I wasnt clear, sorry, occasionally i DONT get the rought idle in the mornings. Please note that its not cold weather but rather starting the car when the engine has completely cooled off. The temp on the dash the other day was 14C

I havent changed the controller, wouldnt i get a fault on all glow plugs? is that something i could tackle myself? When taking apart to access,do i have to replace the gasket on the intake manifold everytime?

Was also thinking of the possibility of a stuck open egr valve, but same thing, no codes...

Injector cleaner? Worth a try?

Injector cleaner won't help and is actually bad for the system as it can dislodge gunk and block up your fuel filter or worse.

A glow plug controller will show in diagnostics as all 6 plugs being faulty. Individual plugs will return individual codes. Very rare for all 6 plugs to fail at the same time so if you get that code, replace the controller. Unfortunately it's in a bugger of a spot under the manifold which is often why people do it all at the same time.

Manifold gasket should be ok if it was only replaced recently.

I think that your issue may be injector related. Could be an injector leaking or dribbling once the car is shut off, loading up the cylinder with diesel, making it hard to start until it clears. Kinda like flooding an old carbureted motor.

Try this - park the car on a steep incline with the nose of the car point downhill. Try the same the next day with the car pointing up hill. If it's easier to start on day 2, it's a good way to diagnose that an injector is flooding the cylinder.


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Thanks Smokey, funny you mentioned the incline... the entrance to my garage is at a steep forward incline, could this be causing the problem even if the car is parked level? When I park the car in the garage I almost always get the jitters, if I park it outside where I don't have the incline I seldom have the problem. I was attributing it to the temperature, it being colder outside made the glow plugs go on for longer and I wouldn't have the problem. The indy has the car parked level and he hasn't experienced the problem...

I´ll give parking on the driveway this weekend and report results. Thanks again.

Well, talked to the indy today and he said they took apart the air intake and the EGR valve. The intake was dirty and the EGR was full of soot. He´s going to give both a good clean and also change the oil and oil filter.

Hopefully that will fix the rought idle problem cause it´s gonna set me back another 400€ :yikes:... Don't know if I´m being taken for a ride here (in his defense the first 400 was my option to change the air filter and all 6 glowplugs instead of changing just the faulty one, from what I´ve been reading it just makes more sense)

I hope I didn't buy a lemon that I´m just gonna keep throwing money at...