Rough idle problem M60, 530i

[Rusty Bavaria]

*I've scoured the archives for an answer to this, but wanted to see if anyone had any suggestions.

I’m having an ongoing problem with my 95 530i with a rough idle problem. It started as a check engine light on cooler mornings at idle after driving for a couple minutes (2-5 minutes) with a slight rough running condition, which would go away after a bit of driving, to currently a hard starting (fluctuating idle) and a continued rough idle even after driving for a good length of time. When the car comes to a stop, it will idle fine for a couple seconds and then slowly degrade into this rough idle eventually will throw the (5-10 seconds of rough idle) CEL. This seems to be much worse in cold weather. When not idling the car drives fine.

The CEL is Lamda control 1 and 2 and then Oxygen sensor 1 and 2.

I have looked for intake leaks, found the intake boot to have a crack at the ICV elbow and replaced it, improved driving didn't completely get rid of the rough idle

Replaced oxygen sensors

Replaced spark plugs/coil ends

Cleaned ICV

Checked the connections to the fuel injectors (were disconnected for valve cover gasket replacement over the summer)

Replaced oxygen sensor relay

I have a fuel filter waiting in the garage to replace on the next warm(er) day.

Since replacing the intake boot I’ve had two separate mechanics check for air leaks and neither found anything.

The block was replaced before I bought the car so it is not a Nikasil issue.

Out of frustration this morning I unhooked the MAF sensor which leveled out the loping idle at startup, though I could still feel the rough idle after driving a bit so I think that I just band-aided the problem.

I’ve been hesitant to go the intake gasket route since both mechanics have said that this is not the problem, but I’m running out of ideas, any thoughts?

Thanks in Advance
Jim

[MBXB]

Check the temp sensors and their connectors?
http://www.realoem.com/bmw/showparts.do?model=HE23&mospid=47406&btnr=11_1246&hg=11&fg=35

[Super90]

Are you still throwing codes?

I seem to remember my indy saying that leaking intake gaskets or the PCV plate on the back could falsely cause some of the codes you mention. How do your mechanics know there is no intake leak?

I did my intake seals a long time back with plugs, filters, etc. and my engine idled much smoother after that. Haven't had any real rough idle problems since then. If yours have never been done, my bet is that they are not totally sealing any longer. M60 and M62 motors are notorious for that.

FYI, if you go in for the seals, it's a slippery slope. There are lots of other things you should do while you are in there: galley cover, PCV plate, maybe even the water pump, water pipes, heater hoses, fuel lines etc. etc. I would probably have pulled the injectors and taken then in to the injector shop for ultrasonic cleaning if I had it to do over again. I also did the short (2") power steering hoses that are behind the brake booster at that time. The radiator was out then and that is the only way to get in there.

I did all this in March of 2003 at 100k miles and posted about it then. Doesn't look like "search" goes back that far. I am now at 140k with no idle problems.

I am sure there are some good ways to trouble shoot this, and some others will most likely post to help you out.

[Tiger]

Agreed on intake manifild gasket leak... and the ICV valve which is under the intake manifold...

Check out my other link for rough idle.

http://www.bimmer.info/forum/showthread.php?t=36691

[fin]

I have similar problems, but I get no CEL codes when I stomp test. I may be doing it wrong, but as simple as it is to perform I double it.

Reseating the MAF plug and the plug on top of the engine several times lessened the symptoms.

I was also getting caution lights on the left side of the Instrument Cluster blinking on and off (ASC, Brake fluid level, etc). Looking at the wiring diagram in my Bentley manual the wires seem to all run through the ignition switch. Those too stopped after reseating those two plugs.

As most electrical problems are at the connections, I will keep troubleshooting my problem by unplugging connectors until I find one (or more)that has no effect on engine performance.

The engine was replaced shortly before the problems started occuring which is another reason to check the connections.

Good luck,

Fin

[Tiger]

I would also swap out the MAF to see if that fixes the problem... before I do the manifold work... Manifold diagnosis is easy once your upper cover is off and spray MAF cleaner at the gasket area... do NOT use carb cleaner... will eat plastic.

[e34musician]

I'll have to agree with Tiger on this one. I had a similar problem last year. I spent a week changing all the intake gasket. Only happen to know that it didn't fix my problem. I unplug MAF and extreme rough idle went away.

Faulty MAF can give you weird problem. Try to swap them before you start tearing the old gasket.

[Rusty Bavaria]

Thanks for all the replies
Does anyone have a spare MAF they can loan me to test this out?
I'm in Chicago, and the car is a 95 530i.
(I'll pay shipping it your not local)

Thanks in advance
Jim

[Ross]

PM sent

[zuzuk212]

Hi Jim,
I'm in the chicagoland area and having kind of a similar problem but with a 525.
It seems to happen, dramatically, when the outside temp gets below 25 degrees F, which has been ridiculous here lately.
It will spike the RPM throw a CEL, be ok and then do it again ... Oh, then it will clear the mileage, it retains the info ... just doesn't show, and throws goofy characters in the info section. After it's warmed up, turn it off, let it reset and start it again, it's pretty much fine, except for a slight idle hunt.

Anywho ... I saw this while searching for my problem ... months ago I replaced my head gasket and forgot to plug the air temp sensor back in. It ran without a problem except for the CEL. Plugged in the air temp sensor which rewarded me with a slight idle hunting.

So, you might also want to check your air temp sensor.
Let me know how you make out,

Ken

[fin]

This is good, but still annoying.

My problem went away (for now, I'm sure).

No CEL, no idle dropping below 500 RPM, which seems to cause the electrical system to drop offline. No flashing brake/ASC, etc. lights.

And drives like it should.

So my suspicions of connections being the problem seems to be confirmed. Which one it is is yet to be discovered. As I go through the connections, I will pipe brush them to clean them up, then apply a little dielectric grease to slow corrosion.

Best of luck with yours, please update us when you find the core problem.

Fin

[Rusty Bavaria]

Ok it's been a week (or two) but I was able to spend some quality time with my 530i to look into this idle problem. I tested the coolant temp sensor, has a fine resistance for the temp in my garage so getting low on ideas I started up the car to see what I might find if I could get the car to act up.

It started to act up, and I started spraying the MAF cleaner around the intake, the intake gaskets, the PCV plate...once I it hit the PCV plate, it would smooth out for a second before going rough again. Think I've found my problem.

Now the question: I've heard people mention that they got a engine surge when they would hit the leaky area with MAF cleaner or carb cleaner etc. My idle just smoothed out for a second or two then went back to being rough. I just want to make sure that I'm diagnosing this right before I completely commit to the whole intake gasket replacement thing.

Thanks in Advance
Jim

[MBXB]

Looks like you found the leak. Surge or smoothing out ... depends on what you used to locate the air leak.

[Tiger]

If you can repeat that symptom at the same location, you found the leak. If you are doing intake manifold, then you should do the ICV and the water pump bypass tube... that has an o-ring that will leak in same area... which requires removal of water pump... so if it is old... change it out at this time too.

[632 Regal]

dont forget the front plate gasket, cant do it after everythings back together... how do I know this...