1995 530i Idle Question

[mazzman]

First, I did a search and only found posts with actual idle problems.

My question - Is the M60 supposed to idle somewhat "lumpy"? Just enough that you can slightly feel it when sitting in the car.
Or is it suppose to be smooth and not noticeable when sitting inside?

I have no other issues, Engine sounds fine, does not stall or sputter otherwise. Thanks!

BTW - This is a great site and full of great info. This is the first time I've dived into older BMWs and it's not as scary as some would let you believe. My past experiences were in subarus and 90's hondas.

[moroza]

I've owned three 530i's and a 544. I would not describe a healthy M6x as "lumpy". It should be smooth to the point that you can feel it if you "listen", but just barely.

[K Fox]

Definitely shouldn't be lumpy. That said, there are several things to look at, most of them being things that can cause vacuum leaks. Do a quick search on "M60 vacuum leaks" here in the forum and you'll find lots of info - it's your most likely culprit. For instance, on the back of the engine against the firewall, there is a plate with 2 vacuum caps on it - they tend to crack and leak over time due to living in an engine bay. Might be your issue, or at least a part of it. Knowledge is power - search is knowledge waiting to be gained.



K Fox (guess who's back...back again)

[mazzman]

Thanks for the replies I'll check for vacuum leaks. For the plate - If it's the CCV, I just replaced that so I'll double check the connections. Going from memory I have the large hole capped, the FPR hose connected and the vacuum pump/valve? connected. And it's also connected to the metal pipe under the intake.

[K Fox]

You just reminded me - that drain pipe under the intake can sometimes be an intermittent vacuum leak if it's loose. Get some oil in there and it'll seal up - but once it dry's/drains away, it can leak again. You can just make sure it's seated well against the plate and the clip is on while you're looking around.

K Fox

[Layne]

They're supposed to be smooth as glass, but frequently aren't. Vacuum leaks are #1, as said. Of course the most famous vibration issue is the Nikasil block. I had a 740 with a Nikasil block that vibrated a decent amount, but ran great otherwise. I had a receipt from when the car had 33k miles where the customer complained of a rough idle and they found low compression on the rear two cylinders. Unfortunately the engine was not replaced under warranty for whatever reason, but I ran it up to 230k miles and it still worked fine, still with a rough idle. My current 540 is also Nikasil, but is much smoother.

[mazzman]

Did the starter fluid thing and could not find anything, even around the throttle body. Maybe I'll try again and be a bit more liberal with the fluid. I'm just being cautious about spraying that stuff on the engine.

Still haven't checked the EGR piping at the front of the engine though. Rubber hoses were just replace from the air valve to the CCV.

This is a nik block with 220+K miles. I haven't done a leak down test yet. Compression test in all cylinders were 195-200psi.

The lumpy idle is very subtle. Can't tell from just looking and listening at the engine. I can only feel it slightly when ass is on the seat.

I will definitely keep you guys updated. Thanks again for the help.

[mazzman]

Maybe I was expecting it to be too smooth.??? I didn't mean "lumpy" like a big block V8 with a lopey cam.
Did as much as I can to find a vacuum leak without a gauge and still couldn't find one. I did clean out the IAC valve. Drove it around a lot today and the car runs great. Put in new plugs about 100 miles ago and they look good and look like they're firing. Warm idle is steady at just above the 500RPM mark.

As far as maintenance, I think I'll leave it at that for now...until the radiator spews coolant all over the freeway.