m42 rough idle - need help

[dasfrogger]

The below video is of my 91 318is m42. it's got a rumbly idle (kind of like it's got giant cams), and searches between 500 and 800 rpm at idle - sometimes drops a bit more. Never dies though. Runs and drives with no issues otherwise.

I've also noticed quite a lot of air coming out of the oil filler cap and a change in the idle before and after removing it. Does the m42 have really high crank case pressure, or do I have some blow by? You can see the air coming out of the hole as well as oil splatter. If it is just high pressure, does the change in idle indicate another problem?

Any ideas on what my problem(s) could be?

Took this video tonight.
https://www.youtube.com/watch?v=OUPWxJy7KPY&feature=youtu.be

    *146,100 miles on the stock motor.

   * I've done the mess under the intake recently and have eliminated any vacuum leaks. Double checked via carb cleaner method and wasn't able to affect the idle.

    *Stock injectors should be very clean - run a bottle and a half of sea foam and some lucas injector cleaner.

    *Cleaned AFM, Throttle body, and ICV.

   * Installed spare AFM with same results

    *Unplugged O2 sensor same results. Installed new sensor with same results (however the new sensor's wiring was about 4 inches short and was clearly the wrong part. It has since been uninstalled)

   *the random plug that makes the car run bad is unplugged

   * Oil and filter are fresh 1k miles ago.
   * Spark Plugs fresh 1k miles ago.

[e3091318is]

I have similar symptoms with the oil spitting out a little when I remove my cap, as well as a bit of excessive oil coming out of the vent hole at the top of the valve cover.  I have a 1222 code and ive had it since my rebuild (not sure if it had it before the rebuild or not).  I changed the temp sensor, spark plugs, o2 sensor, cleaned ICV, etc.  The Check Engine light goes away as soon as I touch the gas pedal so I am assuming it is idle related.  Our issue may be related to our throttle body which I am experimenting with. 

As for your air coming out of your cap when it is closed, you may want to get a new cap. 

Do you have any codes?

[romeomike]

The cheapest thing to try first would be replacing the timing chain tensioner.

At 232,000 miles on my M42 (rough idle, failed smog checks), I ended up having a garage do a cylinder head job -- eight new exhaust valves and guides besides the other things that go with a valve job. I have a thread on this board that went through all the other things I did before I bit the financial bullet to get my car running properly again.

[dasfrogger]

I have similar symptoms with the oil spitting out a little when I remove my cap, as well as a bit of excessive oil coming out of the vent hole at the top of the valve cover.  I have a 1222 code and ive had it since my rebuild (not sure if it had it before the rebuild or not).  I changed the temp sensor, spark plugs, o2 sensor, cleaned ICV, etc.  The Check Engine light goes away as soon as I touch the gas pedal so I am assuming it is idle related.  Our issue may be related to our throttle body which I am experimenting with. 

As for your air coming out of your cap when it is closed, you may want to get a new cap. 

Do you have any codes?

Sounds like the air coming out when the cap is removed is normal. No air escapes with the filler cap installed.

I need to reset and check codes. No CEL, but I'm sure it's throwing an O2 sensor code.

The cheapest thing to try first would be replacing the timing chain tensioner.

At 232,000 miles on my M42 (rough idle, failed smog checks), I ended up having a garage do a cylinder head job -- eight new exhaust valves and guides besides the other things that go with a valve job. I have a thread on this board that went through all the other things I did before I bit the financial bullet to get my car running properly again.

When it comes to replacing the Tensioner Should I pick up the guide rails and replace at the same time as the Tensioner piston, or is the piston enough? That job has been on my list, but I was hoping to get a few more miles out of what I had while I saved up some $

I'll have to look into your thread this evening. Thanks!

[romeomike]

The tensioner -- doing the guides would be much more invasive.  You can drop the lower oil pan, and if you have bolts or other parts sitting in the pan, then the case for doing the guides would become much stronger.

Here's the thread I was referring to

http://www.m42club.com/forum/index.php?topic=18215.0

[dasfrogger]

The tensioner -- doing the guides would be much more invasive.  You can drop the lower oil pan, and if you have bolts or other parts sitting in the pan, then the case for doing the guides would become much stronger.

Here's the thread I was referring to

http://www.m42club.com/forum/index.php?topic=18215.0

Thanks for the info! Looks like I need to get a parts order together.