BMW Z4 2.0 rough idle

[Phil Coleman]

Can anyone help me with this please ...

Had my Z4 since October, really happy with it but it has a little niggle. The car drives really well but when it's stood idling the engine seems to sound quite rough ... makes kind of a pop pop pop pop sound. As soon as you move off again, the normal engine sound resumes. It doesn't seem to do it when you switch the engine on and the automatic choke is on. On idle the rev counter stays around 900rpm's and is steady and doesn't move. When I'm driving and come to a stop the rev counter kind of jumps a couple of 100 revs for a second or two and then it settle on 900rpm.

Thoughts are either idle control valve, the MAF, spark plugs or a vacuum leak? Has anyone had a similar problem or has idea what it could be? Any help or thoughts would be appreciated.

Ta

Phil

 

[andyfanshawe]

Hi Phil.
Welcome to the 2 litre club! They are the best!
Does sound like an air leak, but need to look at live data on a suitable scanner to be certain, unless you want to throw parts at it!
I'm only in Chesterfield so could easily plug a scanner in and have a look. I have a smoke machine that can detect air leaks easily.
They are very, very, very sensitive to oil condition, so make sure it is clean and at the right level.
No IAC valve cos its fly by wire throttle. No auto choke either!! Don't change the MAF.
Ive come across a few with a slightly loose oil cap that has caused idle problems.
I'm assuming it has good service histroy and up to date.

Andy.

 

[andyfanshawe]

Just to update people on this........FIXED.
Pretty simple one to diagnose. I knew what this was as soon as it pulled into my workshop.
Can you guess?........valvetronic motor.
Tell tale symptoms are an engine that stumbles when you lightly blip the throttle. Blip to only 1500 rpm. As you would when pulling away from a junction.
Oh, and of course, a rough idle.
Hoping Phil will chip in here for an update.

Andy.

 

[Ducklakeview]

Just to update people on this........FIXED.
Pretty simple one to diagnose. I knew what this was as soon as it pulled into my workshop.
Can you guess?........valvetronic motor.
Tell tale symptoms are an engine that stumbles when you lightly blip the throttle. Blip to only 1500 rpm. As you would when pulling away from a junction.
Oh, and of course, a rough idle.
Hoping Phil will chip in here for an update.

Andy.

Nice one Andy, also had to swap one on a 2.0 myself last week, same symptoms. Idle was so lumpy the gearstick could be visibly seem to be moving about..

Mike

 

[andyfanshawe]

Nice one Mike. troublesome little creatures they are.
I think Phil paid about 130 quid ish for a "genuine" one on ebay. Looked very good quality. Fitting pretty straightforward.
Are you busy with the zeds?
Ive got another sticky steering coming in next week!!!!!!
Andy.

 

[Ducklakeview]

Nice one Mike. troublesome little creatures they are.
I think Phil paid about 130 quid ish for a "genuine" one on ebay. Looked very good quality. Fitting pretty straightforward.
Are you busy with the zeds?
Ive got another sticky steering coming in next week!!!!!!
Andy.

Yup, they are keeping me busy! Seeing a good few 2.0's!

Mike

 

[jonnya93]

Hi All,

Just got myself a Z4 2.0 (06 plate) and have a similar issue to the above.
On starting, the idle speed remains above 1000rpm for a good 45 seconds to a minute before ‘settling’ at around 800-900rpm.

It’s lumpy to the point the gear leaver is visibly wobbling/vibrating and there are occasional ‘blips’ where the revs jump a few hundred rpm before dropping again

Does this sound like valvetronic motor needs replacing?

Thanks

 

[Smartbear]

Hi All,

Just got myself a Z4 2.0 (06 plate) and have a similar issue to the above.
On starting, the idle speed remains above 1000rpm for a good 45 seconds to a minute before ‘settling’ at around 800-900rpm.

It’s lumpy to the point the gear leaver is visibly wobbling/vibrating and there are occasional ‘blips’ where the revs jump a few hundred rpm before dropping again

Does this sound like valvetronic motor needs replacing?

Thanks

You need to get the car scanned to check for fault codes, or it’s just expensive guesswork.
Rob

 

[jonnya93]

You need to get the car scanned to check for fault codes, or it’s just expensive guesswork.
Rob

It was plugged into a diagnostic reader and no faults came up at all

 

[Smartbear]

You need to get the car scanned to check for fault codes, or it’s just expensive guesswork.
Rob

It was plugged into a diagnostic reader and no faults came up at all

Was it a decent one or just a cheap generic type reader? Those don’t always read the stored codes.
Rob

 

[jonnya93]

jonnya93 wrote: ↑Mon Jul 13, 2020 5:51 pm
Smartbear wrote: ↑Mon Jul 13, 2020 4:42 pm
You need to get the car scanned to check for fault codes, or it’s just expensive guesswork.
Rob
It was plugged into a diagnostic reader and no faults came up at all
Was it a decent one or just a cheap generic type reader? Those don’t always read the stored codes.
Rob

It was a proper tester at an independent garage

My brother works at BMW (Mini Plant, Oxford) so i'll get him to plug it into his work laptop/reader and see what that throws up

Thanks

 

[Kev653]

Hi, first time on here so not really sure if i can help but here goes. I have a 2.0 convertible 2006 bought in the middle of the pandemic as a get out of the house excuse during lockdown and had the same problem. I read a few posts on here regarding the lumpy idle and decided to change the camshaft position sensor and also the idle control valve, air supply sensor. Problem solved so thanks to whoever had posted it previously.
I fell in love with this car instantly so after reading a few more posts decided to buy a z4 3.0si coupe. Best thing I’ve ever done. I love the little 2.0 for popping around the country lane ear where I live but when im alone I take the coupe for some fun.
Thanks guys.

 

[Jfgoldfish]

I read a few posts on here regarding the lumpy idle and decided to change the camshaft position sensor and also the idle control valve, air supply sensor. Problem solved

Hi kev,
I'm interested in which parts you replaced. I'm experiencing similar symptoms and would like to solve this slightly rough idle.
Did you replace both camshaft sensors?
When you say 'idle control valve', which part do you refer to? There isn't technically an idle air control valve on these engines.
J

 

[Kev653]

Hi jf goldfish please bear with me I don’t do social media or forums etc but having been bitten by the z4 bug i like the idea of being able to learn more about the cars from guys who have experience.
I replaced camshaft position sensor and crankshaft pulse sensor apparently ( sorry im a Brickie not mechanical at all, but i did manage to change them myself. The idle control valve i ordered arrived but I don’t know where on the engine it is. Obviously if there isn’t one then theres the answer
I bought them from AUTODOC website
I hope this helps

 

[Jfgoldfish]

Evening kev,
Thanks for getting back to me.
I'm not a big fan of social media either, so don't worry, no judgements from me!
Autodoc is a great site, their prices are unbeatable. I think their system might have miss-sold you the idle air valve; I might be wrong, but I don't think their actually is one on this engine. Luckily it looks like it isn't a very expensive part.

Anyway, that aside, you have replaced one of the camshaft sensors and the crankshaft sensor so far and that seems to have somewhat cured the rough running? I will check the sensor outputs on mine this weekend and consider ordering some replacements.

 

[Kev653]

Hi, i did them within an hour yesterday and the difference was unbelievable. It sits quiet and idles smooth. Its got 114000 miles on it with a comprehensive bmw history and when i bought the 2.0 i asked a local bmw specialist to replace the top end gaskets to eliminate the usual oil smell on start up as well as the vanos solenoids, full major service and complete new brakes all round. I always loved these cars when i was a young lad but never had chance to own one until I became an old bloke lol. I take them out at every opportunity, just great fun. I know the 2.0 gets some ribbing on here but on a sunny day with the roof off it’s just fine by me.