Progress on the BMW is slow. Unfortunately I fix one thing, and in the process find something else that is broken and needs more parts ordered.
The idle was still rough and it bothered me. It’s not like I don’t enjoy the sound of a nice lumpy cam, but the car shouldn’t idle like that, so something was wrong.
According to this, the idle valve is shut, and not passing any air, yet it is still idling. It should be between 8 and 18 kg/h, not zero. As it states, if the reading is below 10, check for unmetered air. Unmetered air is any air that enters the intake after the airflow meter, so it’s not measured by the airflow meter. This is usually caused by loose hose clamps, cracks in hoses/pipes, or a failure in the Crank Case Ventilation system (CCV).
I had previously cleaned and checked the idle valve, so I knew that moved freely, and I could get the idle valve reading to change by opening and closing the throttle, so obviously the valve operates, it’s just not “needed” at idle.
The obvious points in the intake to look at are the intake piping and elbow between the airflow meter and the plenum. The elbow especially is prone to cracking, but after a thorough check my intake piping and elbow were fine.
So the next thing was to remove the whole intake again, replace all the CCV parts/hoses, vacuum lines and O-Rings and see if that fixes it.
I noticed last time I had the intake off that the CCV was looking rather ugly, with a coating of old oil on it. I did check and tighten the hoses, but that obviously didn’t make a difference. You can see it tucked behind the idle valve
I had ordered a bunch of parts for this job, so set about replacing the ICV piping and CCV.
Both hoses on the idle valve had also softened a bit, but were in useable shape. Unfortunately I missed ordering the hose on the left in the photo, so had to reuse the one on there, but it was in good condition anyway.
One of the hoses has this weird metal plug in it. Not sure what it’s normally for, maybe something emissions related? When I fit the replacement hose, I put a small clamp on that plug too, just to be sure it wasn’t leaking
I found it very hard to find information on these o-rings, so had to order from BMW instead of using generic ones of the correct size. So, here are the sizes for future reference.
No photo of it, but the Fuel Pressure Regulator vacuum hose got replaced too. That is in one heck of a nasty place to get to! It wasn’t cracked, but was hard and would’ve failed eventually.
Since the intake was all apart, one thing I wanted to try was to smoke test the throttles/vacuum manifold and see if there were any leaks post throttle. Since the previous owner had these off the head, I had my suspicions that maybe there was a leak there. There was certainly some precedence for them doing it wrong…
I read on another forum about smoke testing using a small container (jar in this case), some incense, and hose. Light the incense (I used cones as they are smaller and fit better in the jar), blow it out so it smokes, pop it in the jar, wait for it to fill the jar with smoke and then with one hose leading to the intake, blow into the other hose. This blows the smoke into the intake, and if it finds a way out, it’ll be obvious where it’s leaking from
I can confirm there are no leaks post throttles now, which is good. I haven’t tested with the plenum and intake piping in place yet, but I’ll do that next time I have the MAF (airflow meter) out. If it’s all sealed, there should be zero smoke escaping.
With the intake off I took this chance to replace the starter motor, since it hides under the intake, and was intermittently not starting the car. I will have another post on that job though. It was not fun.
One last thing to replace was the fan clutch. The one on the car was locking when cold, causing the engine to run cooler than desired, and making a hell of a racket. I finally gave in and purchased a proper 32mm fan clutch spanner off Trademe. This made the job too easy, and I now wonder why I never got one earlier.
My replacement I picked carefully. There are a lot of knock off clutches around which don’t operate correctly, so after much research I went with the tried and true Hella/BEHR unit. This is widely regarded as one of the best ones to buy. It also has the proper bimetallic strip on the front, unlike the knock offs which usually have a spiral. It wasn’t cheap, so it better be good!
So after all that work, what are the results? Good news, the fan clutch works perfectly. Bad news, the idle is still lumpy. Strangely, the car runs and drives like a bat outta hell, and pulls very hard, but it just wont idle smoothly.
I need to run the DIS test again to see if the idle valve is working properly or not now, and I also need to smoke test the whole intake. At this point though I have decided that I’m just going to drive and enjoy the car, without worrying too much about the idle. I want to check the valve clearances in the future, as I doubt they have been done, but I’ll leave that for future Me to sort out.