[baron62]

I have a 2008 E90 non turbo with 115K miles and occasionally it has a rough idle for a few seconds. The engine never stalls and actually bumps up RPM temporarily after the initial RPM dip. Power seems smooth and normal when accelerating. This has been going on for about a year. This is an intermitant problem that does not surface on some drives. Code reader shows no codes. I tried fuel injector cleaner additive and that did not resolve the problem. Plugs were replaced 40K miles back. Any suggestions on steps I should take to troubleshoot?

[lowrydr310]

Originally Posted by baron62

I have a 2008 E90 non turbo with 115K miles and occasionally it has a rough idle for a few seconds. The engine never stalls and actually bumps up RPM temporarily after the initial RPM dip. Power seems smooth and normal when accelerating. This has been going on for about a year. This is an intermitant problem that does not surface on some drives. Code reader shows no codes. I tried fuel injector cleaner additive and that did not resolve the problem. Plugs were replaced 40K miles back. Any suggestions on steps I should take to troubleshoot?

It could still be plugs/coils but it's difficult to diagnose without any codes. It could also be a minor air leak in the intake or PCV plumbing, a dirty MAF sensor, cam sensor, or eccentric shaft sensor, though any of those sensor issues would usually trigger a code right away. Have you ever cleaned or replaced you VANOS solenoids? That might be a good place to start.

[baron62]

I have not cleaned or replaced the VANOS solenoids.

[CTinline-six]

I would start with cleaning the solenoids. They are located right on the front of the engine and each one is held in with a 10mm bolt, so it is a fairly easy job.

Have any of the coils been replaced? Is your valve cover gasket leaking? I had a cracked plastic valve cover on my 328i, and besides smoking I think it also created rough running from a vacuum leak and also oil could've been leaking into the holes where the spark plugs are, causing rough running.

Where in CT are you located? I'm near Storrs/UConn and would be happy to stop by and help out if you are close by.

[baron62]

I looked up the videos on cleaning the soleniods and will clean them. What is the role of these solenoids on a BMW? I generally know what a soleniod does, but not in this application.

I did replace the valve cover gasket a few years ago and that was a 10 hour job for me. Ran fine afterwards. I have never replaced any coils, but have a spare one ready to go.

CTinline- I am in Canton, but went to school at UCONN. Nice area.

[ny325]

This usually happens to me when temperatures drop below 37 degrees.

[lowrydr310]

Originally Posted by baron62

I looked up the videos on cleaning the soleniods and will clean them. What is the role of these solenoids on a BMW? I generally know what a soleniod does, but not in this application.

From Pelican Parts:

The BMW E90 engine utilizes two VANOS (variable camshaft timing) solenoids. One for the intake camshaft and one for the exhaust camshaft, mounted to the front of cylinder head. They are responsible for direct oil flow to the VANOS actuator and can become restricted over time on high mileage engines.

What is VANOS?

VANOS is a variator system that varies the timing of the valves by moving the position of the camshafts in relation to the drive gear. The relative timing between inlet and exhaust valves is changed.

At lower engine speeds, the position of the camshaft is moved so the valves are opened later, as this improves idling quality and smooth power development. As the engine speed increases, the valves are opened earlier: this enhances torque, reduces fuel consumption and lowers emissions. At high engine speeds, the valves are opened later again, because this allows full power delivery.

So if those solenoids are clogged or not opening/closing properly, your timing may not be adjusted correctly when commanded by the computer, which *may* cause rough idle or numerous other symptoms. When they're broken you'll likely get a check engine light along with accompanying codes, but if clogged/dirty/sticky/starting-to-fail you could see intermittent issues (with no engine light) like what you're experiencing.

[baron62]

Thanks everyone. I removed both Vanos Solenoids and cleaned them the best I could with brake cleaner. Couple of test rides and it is still there at idle and it is worse when cold. Appears to only be a low RPM issue. I need to get a better code reader...no codes found!

I just ordered a set of VANOS solenoids Qyt: 2 - 11367585425 from eEuroparts. I'm trying their non-genuine parts. Will report back. Hope this it! They do come out easily.

[Bimmer_Engineer]

Hmm...I’ve never heard of eeuroparts before but I just checked them out and they seem to have the lifetime warranty like fcpeuro. The couple of things I checked (oil filter, belt kit, and coils) were cheaper too...

[gbalthrop]

Originally Posted by baron62

I have a 2008 E90 non turbo with 115K miles and occasionally it has a rough idle for a few seconds. The engine never stalls and actually bumps up RPM temporarily after the initial RPM dip. Power seems smooth and normal when accelerating. This has been going on for about a year. This is an intermitant problem that does not surface on some drives...

Does the issue seem to be related EITHER to engine temp, or ambient/outside temp?

Have you had the Crankcase Breather Heater recall performed?

Have you checked to see if your O2 Sensor Heaters (on the same fuse as Crankcase Breather Heater, F38 on 2008 model 328i) are getting voltage supply per this TIS circuit diagram?
https://www.newtis.info/tisv2/a/en/e...8-fuse/vFbq6N3

Just some random things to check when no codes. Many intermittent ragged idle issues are related to vacuum leaks in intake, oil being sucked into the intake, Valve Cover or PCV valve (incorporated in cover) issues, breather heater issues, etc.

George

[sorin1987]

Originally Posted by baron62

Thanks everyone. I removed both Vanos Solenoids and cleaned them the best I could with brake cleaner. Couple of test rides and it is still there at idle and it is worse when cold. Appears to only be a low RPM issue. I need to get a better code reader...no codes found!

I just ordered a set of VANOS solenoids Qyt: 2 - 11367585425 from eEuroparts. I'm trying their non-genuine parts. Will report back. Hope this it! They do come out easily.

I've experienced rough idles a few times and they were never from the VANOS. I tried cleaning them just like you did and nothing improved. Since you ordered them already I guess you can go ahead and change them anyway. How much did you paid for the non OEM ones?
Anyway in my case the two times I experienced rough idles were a cracked valve cover and this came with a check engine light and sometimes the big "engine operates on reduced power" warning.
Second time was because of 2 malfunctioning injectors. They were leaky over night and the rough idle would go away after 5-10 mins of engine running. Anyway I had to change those in order to get the car working fine again.

By the way, I think VANOS will throw some specific codes if they are malfunctioning.

[lowrydr310]

Originally Posted by sorin1987

Second time was because of 2 malfunctioning injectors. They were leaky over night and the rough idle would go away after 5-10 mins of engine running. Anyway I had to change those in order to get the car working fine again.

The leaky injectors were on a N52? How did you diagnose that? Was there fuel leaking around them, or were they allowing air inside?

I too am diagnosing an idle issue. I wouldn't call it rough because the two failed coils I experienced with only 4 out of 6 cylinders firing is a rough idle, however my idle causes things to buzz/vibrate. If I increase revs to 900 or so it's perfectly smooth. I also get a slight pinging under heavy load at low RPM. I'll often drive in DS mode to avoid lugging the engine to prevent this. No codes, no SES light, nothing. Aside from this the engine runs great, gobs of N52 power and very smooth delivery.

I'm also consuming oil and not sure why. I haven't inspected my crankcase ventilation plumbing yet but I plan to do that soon.

I bought my car with the bad coils and misfire. The previous owner drove it with the misfire but I don't know how long. If it was driven a while with the misfire, is it possible I have a stuck ring? There's no visible smoke out the tailpipe ever, even under very heavy acceleration.

[baron62]

I replaced the vanos soleniods and the problem has not gone away. Intermitant rough idle. Sometimes it idles smooth at a stop and sometimes its rough going up/down 200 RPM. Never stalls. No codes on an OBDII reader that works. Could a fuel injector do this? Any ideas?

[drawz]

Originally Posted by baron62

I replaced the vanos soleniods and the problem has not gone away. Intermitant rough idle. Sometimes it idles smooth at a stop and sometimes its rough going up/down 200 RPM. Never stalls. No codes on an OBDII reader that works. Could a fuel injector do this? Any ideas?

Find someone to help you read the BMW specific codes. You can do this with a variety of tools.

[sorin1987]

Originally Posted by lowrydr310

The leaky injectors were on a N52? How did you diagnose that? Was there fuel leaking around them, or were they allowing air inside?

I too am diagnosing an idle issue. I wouldn't call it rough because the two failed coils I experienced with only 4 out of 6 cylinders firing is a rough idle, however my idle causes things to buzz/vibrate. If I increase revs to 900 or so it's perfectly smooth. I also get a slight pinging under heavy load at low RPM. I'll often drive in DS mode to avoid lugging the engine to prevent this. No codes, no SES light, nothing. Aside from this the engine runs great, gobs of N52 power and very smooth delivery.

I'm also consuming oil and not sure why. I haven't inspected my crankcase ventilation plumbing yet but I plan to do that soon.

I bought my car with the bad coils and misfire. The previous owner drove it with the misfire but I don't know how long. If it was driven a while with the misfire, is it possible I have a stuck ring? There's no visible smoke out the tailpipe ever, even under very heavy acceleration.

After changing spark plugs, coils and cleaning vanos solenoids without result I took the car to a garage that specializes in BMW. The engineers there were able to tell me that the injectors were faulty said that it is a known issue with the original E90 injectors. They leak a little bit of fuel after the engine is stopped and they don't operate at the correct pressure for the first few minutes of the engine running. Hence the rough idle that settles down after a few minutes. This happens regardless of the hot or cold weather.
I had to change one bank (injectors 2,4,6). Car worked fine and now it started to do the rough idle again as the engineer warned me that it would happen...the other 3 will go soon to but it was damn expensive and I tried to reduce the cost. I was hoping to sell this terrible car but I was busy and haven't got the chance. I will probably run it like this for a while, then replace the 3 injectors and sell it as I believe it is not worth the running costs.

[agustincuenca]

as some said, I'm also inclined towards the VANOS. Had exact same issue for a while and it's completely gone after installing 2 new solenoids. It's a 10 minutes DIY and I bought the OEM ones for less than $300 from ECS (slightly cheaper than FCP).