I am fairly new to this forum and have found it very helpful for DIY on my car. I apologize if the following post has been addressed somewhere else on this forum (I have researched but yet to find a clear cut answer).
My car now shudders a little during cold start. I notice the rpm go down and up and the engine vibrates/shudders quite a bit. However, once the engine is warm - or after driving for some time - the problem goes away. I spoke to my Indy shop and they suspect it could be a clogged idle control valve. I have seen a couple posts of this nature on this forum; but with little info on solution (it seems this could be caused by multiple factors). From the little research I have done, I also understand there could be a vacuum leak or a problem with the VANOS.
I should also add that my Indy had earlier reset the code on the idle control valve but that hasn't helped. Before paying the king's ransom to replace/clean the idle control valve, I would like to hear what the experts have to say. I also have a short video which captures the rpm in problem state - you'll notice the rpm bounce down and up (and I feel the shudder/vibration). Happy to answer any questions. Thanks for your help!!
https://youtu.be/BvZ81DV542Y
Last edited by julls; 02-13-2018 at 01:52 PM.
Welcome!
tip for you: You need to tell people the important things like what engine you have, miles, year etc.
Thanks NoQuarterX. My car is E90 2006 330i with 192k miles. I should add that I called up my Indy again today and asked why he thought the problem might be with the idle control valve - since the problem goes away after the engine warms up/after driving a mile - he didn't quite have an explanation for that. So I'm a little on the fence that the idle control valve should be the first thing he should be checking - but then again, what do i know? Appreciate any input on this.
My Indy diagnosed the issue today and has concluded that the problem is with the valtronic shaft sensor. He says it needs to be replaced and I'm told this job will take 5 hours. This sucks big time because I had Indy replace my valve covers gasket and valve cover gasket bolt kit only two weeks ago. I mentioned this problem then but Indy never really looked into it - I only found out the next day after picking up my car. Had this been diagnosed during the last job, I wouldn't be spending money on 5 hours worth of labor just to replace the sensor since it could have been easily replaced then. Parts and labor for this job comes down to around $1200.
Last edited by julls; 02-19-2018 at 04:50 PM.
Quick update:
$1200 later, I was still having the issue despite changing the valtronic shaft sensor. In fact the issue became more pronounced - I would observe the idle surge almost every time I stopped at a red light. Took the car back to the shop and it was suspected to be a fuel pump issue - which has now been replaced. Picked up the car earlier today and few minutes later, noticed the same problem. I decided to pick up Seafoam injector cleaner; drove the car for more than an hour; stopped a few times; parked for some minutes and haven't seen the problem. Could this be pointing to a faulty/clogged injector?
Have you checked;
Spark Plugs - condition and gap (mine were over gaped and provided this symptom on cold starts only)
Ignition Coils - condition, age?
I'm not sure if my Idy checked those - I had it in mind to ask the shop about checking the ignition coils but I haven't seen the problem since using Seafoam. I find it odd that the problem has gone away (though not sure if this is permanent) with just an injector cleaner.
This is a common issue and particularly with higher mileage e90s. I personally have the same exact problem for about 30k mi and it's been more a minor annoyance than a real problem. I have a 2007 328i with 136k mi. It's more pronounced cold. It primarily happens at idle. The engine RPMS briefly drop, seems to stumble/hiccup and vibrate about .5 seconds but recovers quickly. I can make it do the same thing going from higher RPM to low RPM suddenly when cold seems to trigger it as well (this to me suggests VANOS). It seems to accelerate just fine. Mine has never thrown a code (I scan with Rheingold).
Personally, I'd put my time/money on aging VANOS units. The VANOS system seems to cause low RPM engine problems and is heavily dependent on oil pressure to function correctly. Check out this youtube video for symptoms (https://www.youtube.com/watch?v=tWKX97gHFlc&t=2s). The solenoids are a good place to start. They control oil flow to the VANOS system and get gunked up restricted resulting in slow VANOS response. They're easy to remove, clean, and replace ($100 each?). Plenty of DIY info out there such as https://www.pelicanparts.com/BMW/tec..._Replacing.htm. Camshaft position sensors can also go bad (I'd expect a code though) and are easy, cheap ($60?) to replace. See https://www.pelicanparts.com/BMW/tec..._Replacing.htm. Finally, the internal VANOS unit seals (not solenoid seals) tend to leak. Well known problem with VANOS units. As far as I know, BMW does not sell these and they're not available from third parties and requires replacement of the units at about $550 each without labor. I plan to clean my solenoids in the next week or two to see if I get improvement. I'll sure as hell wait until I get codes before I replace a VANOS unit though :P
For completeness, others have spoken on the topic. The most talked about and likely cheapest solution seems to be recoding the idle RPMs up about 100-150 rpms. Of course, that doesn't really *solve* the underlying problem. Several folks have claimed aftermarket Bosch plugs were to blame (cheap/easy to replace yourself). Several folks claim it's dirty MAF sensors (cheap/easy to clean yourself). Some claim its failing coils (not so cheap, but easy). Others have replaced all these to no avail. I highly doubt coils/plugs/fuel pump or regulator are to blame since mine seems ok under load.
Thanks for the detailed information awj - really appreciate it. Yes, this is annoying and irritating to me as well. Mine started out to be a cold start issue but then right after replacing the valtronic shaft sensor, it seemed to happen ALL the time - on cold and hot engine. I've read threads where the finger of blame was being pointed at the VANOS but since I didn't see any error codes on mine, I was reluctant to replace it. My Idy claims there was an error code for the valtronic shaft sensor - which is why we replaced it in the first place - but here I am $1200 later. I also agree that this might have nothing to do with the fuel pump - Idy claimed he ran a test on my fuel pump and the results had an anomaly so we replaced the pump as well; all to no avail. The last time I spoke to Idy, he said he is happy to check my coils and plugs. He has an actual testing device for the coils. I will check out the youtube video and the DIY you posted just in case this problem resurfaces again. I haven't seen the issue since I threw in SeaFoam and I'm likely going to switch from using Shell V-power to Chevron Techron. Thanks again for the input. I will definitely cycle back with any updates - if anything changes.
Last edited by julls; 03-15-2018 at 01:51 PM.
I had a chance to pull my Vanos solenoids and clean them. I just soaked them in gas and sprayed with brake cleaner and compressed air to dry. The brief RPM drops and corresponding shudder have definitely stopped, even on cold mornings at around 35 F.
Thanks awj. My rough idle issue resurfaced again - I got a new Indy to clean the Vanos solenoids but that didn't make any difference. He is going to change my coils tomorrow and we will test further. Will cycle back.
New Indy cleaned the vanos soleniods but that didn't do the trick. The shop proceeded to replace the coils and spark plugs - car runs like brand new now. I wish I had started from there before throwing in the king's ransom on the crankshaft sensors when this issue first started back in February. I'm going to post back here if I run into further issues; hopefully I don't
Last edited by julls; 04-03-2018 at 04:48 PM.
VACCUM LEAK can do that too.. my 06 e90. I would turn it on it would be super sluggish would have a nasty idle until i drive it for 1 km basically with the vacuum leak my engine would be revving to 5000 but i aint going no where then it would go back to normal like nothing ever happened and when im in park you dont notice the car is even on... i would check that it would also cause random misfires
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