I was going to make this video myself, but since it is already made ...

My car threw a 2187 ( lean air mixture ) error after a local garage removed and replaced the valve cover as part of a timing chain tensioner replacement. The car threw the error the morning after the repair and had a very rough idle, especially when cold. After my local mechanic did a smoke test and checked the vacuum lines he suggested that the issue might be the PCV valve in the cover. He verified this by doing the above linked test which showed no crankcase vacuum at idle. Not wanting to replace the cover I ordered the PCV valve replacement from ECS. The morning I went out to replace the PCV valve in the cover the rough idle at cold start was not there, but the code was there and I could not delete it with my Scan Gauge, so I warmed up the car, checked the vacuum (none), and proceeded to replace the PCV in the cover. When I opened the PCV cover the original PCV plastic looked brand new, but I replaced it, put the new cover back on and when everything was put back together..... still no vacuum. I bought a mini specific comm (I put a link up to that here on the forum $49 on amazon) which was able to clear the code and after driving a total of about 400 miles, the code did not come back, despite no vacuum in the crankcase.

A fellow board member put the car on his very impressive computer and did not pull any codes.

In the 400 miles the car only struggled at idle once or twice. It does Idle around 870 RPM and throws, a "little" more white smoke than it should for a fully warmed up car ( not a lot, but noticeably more than other cars I'm idling nearby.

Another thing that I don't get, If there is no vacuum, then why does the idle change so much when I remove the cap? Isn't no vacuum, no vacuum?
Good advice is usually, if it ain't broke don't fix it, but this is buggin' me.

 

Your not supposed to have vacuum to the crankcase at idle. Others may chime in if I'm incorrect. Vacuum under the valve cover at idle IS the sign that the pcv has failed.

 

If that was true, then wouldn't removing the oil cap at idle result in no change of the idle? Since no vacuum/pressure change would result in removing the cap?

 

Yes that's true, removing the oil cap shouldn't change the idle and be sucked to the cover. There is a spring inside the pcv that holds it closed until engine speed picks up and vacuum increases. This then can overcome the spring and allow vacuum to the cover. N14 engine correct?

 

Pcv diaphragm is not serviceable on the N14 engines.

 

Here is a dumb question? If the purge valve was stuck open would that effect Idle vacuum?

I don't overfill the tank and the cap is in perfect condition and properly closed, but after I fill up (not always) the car cranks for a long time and I need to hold down the gas pedal to keep it from stalling out. After a few minutes the car is back to normal.

I monitor the A/F and it is running slightly rich, it bounces back and forth between 14.6 and 13.7.

 

Sounds like it could be the HPFP

 

Have to point out this problem was likely caused by the work you had done on the engine. Last thing touched...

If you are measuring no vacuum, low pressure, but you remove the oil filler cap and the engine reacts, that could be because you are checking for vacuum/low pressure at the wrong place.

It has been my experience over the years even before emissions vacuum/low pressure is greatest (lowest?) at idle although a closed throttle coast down from speed might have the vacuum/low pressure about the same as idle.

You need to check for vacuum leaks. The smoke test is one way. In the days before smoke the trick was to use a can of aerosol carb cleaner and spray this at where the intake manifold bolted to the head, at various hoses, where they connected, just every inch of area that is exposed to the vacuum of the intake/crankcase. If a vacuum leak is hit with the spray the engine should react either by speeding up a bit or by slowing down a bit, stumbling.

If you get a reaction that's where the leak is.

Vacuum hoses fail along their bottom and close to where they fit over the hose connection. Gently pick up each vacuum hose and see if by picking it moving it about *gently* you can get the engine to react.

 

N12 port injected engine, No HPFP, DI engines need HPFP to overcome compression. Turbos got direct injection, standard engines did not.

I suspect as much, but if your tire goes flat after you fill up with gas .... My scan gauge A/F is bouncing back and forth between 14.6 and 13.7 while driving. Sometimes when I come to a stop it idles 11.? till settling down at the 13.7/14.6 ratio after a minute or less. This suggests to me that there is a small leak somewhere. After doing a bunch of reading I am suspecting either the breather hose (have to remove intake manifold on the N12 to replace) or the purge valve (have had a few very hard start after fill up issues, the gas cap is fine). I may, however try the carb spray (was done by my mechanic before smoke test) and move the vacuum lines while the car is idling to see if I can get a reaction.

If the issue was the valve cover gasket I would think taking the oil cap off wouldn't make that much of a difference. Though this does seem to be a small leak for now so who knows, that may have to be checked too at some point. I read somewhere else here on the forum where someone had put sealant on the inner gasket rings and had a similar issue to this until he removed the valve cover cleaned the gasket put the valve cover back on ....

This won't happen till the weather warms a bit ( was 5 degrees this AM ), which is why I took it to a mechanic in the first place ( just call me a cold weather wimp, I don't mind )

 

N12? Yep no hpfp, i keep looking at that video of the N14 engine you posted.

 

Do you have an update? My PCV looks fine to me but there is a vacuum under the oil cap at idle.