94 540i rough idle

[ammo00]

Was wondering if any one can help me out. Just bought a 94 540I about 6 months ago. It has developed a rough Idle over the past few weeks. It started out idling rough at start up and then would idle smooth after about 2 to three minutes. It has gotten progressively worse. Now it idles rough at start up and continues to do so. Here is something else I have noticed about the situation. When I first start it it runs rough, if I shut it off right away and restart it will idle smooth for 30 seconds or so then go back to the rough Idle. After it warms up it runs alittle better but it is still rougher than i think it should be or when i first bought it.

Willie

[Johntee540]

2 Questions first. 1) How many miles are on the car? 2) Did it just recently turn cold where you are?

It sounds like 1 of 2 things. o2 Sensors or Intake Manifold Gasket. There is a Vacuum leak in the IMG that when the weather is cold gets exposed. The cold contracts the gasket opening up the leak. This causes rough running until the engine warms up and the heat expands the gasket closing the leak - allowing the engine computer adjust the engine to run normally. - JT

[bpattan]

Nikasil. you probably have a Nikasil engine block, as i do on my 530. ther's lots of info on this formum about Nikasil. To confirm this have it checked out by a bmw dealer or other shop. if you have less than 100,000 miles you may still qualify fora new engine, made of Alusil. some bmw dealers have a inventory of new blocks, i just priced one here in Houston, $3,800, just for the shortblock. good luck, if that's your probelm you have two options. 1) live with it, 2) replace the block. bob :(

[632 Regal]

everyone on this board with Nikasil blocks have that same problem.

I dont think so.

Check for vacuum leaks from the air box to the intake, all the small hoses too.

[ammo00]

150K mi. It just turned cold but I noticed the problem before it did turn cold. The later of the problem has been going on since it got colder. The intake manifold gasket has been replaced recently. I was in the process of getting the O2 sensors to replace them. I will let you know when they come in if that was the problem. Thanks

Willie


2 Questions first. 1) How many miles are on the car? 2) Did it just recently turn cold where you are?

It sounds like 1 of 2 things. o2 Sensors or Intake Manifold Gasket. There is a Vacuum leak in the IMG that when the weather is cold gets exposed. The cold contracts the gasket opening up the leak. This causes rough running until the engine warms up and the heat expands the gasket closing the leak - allowing the engine computer adjust the engine to run normally. - JT

[632 Regal]

thats why I say to thoroughly check for vacuum leaks first.

[SharkmanBMW]

when my 540 had rough idle for the first 2-3 minutes - then it would smooth out.... it was the pcv plate on the back of the intake manifold, now it is fine!

[Johntee540]

Not everything points to Nikasil. Sheesh. This sounds more like a vacuum leak than anything else. Lets start the diagnosis cheap and work towards the expensive. - JT

[Johntee540]

The rear of the intake Manifold is also a great hunting ground for Vacuum leaks. Also - all of your hoses are old and are biodegradeable. They will start to leak over time as well. At this point in the life of your car you will need to invest some time in making sure that there are no leaks whatsoever in the vacuum channels. Good luck - JT

[DueyT]

Nikasil. you probably have a Nikasil engine block, as i do on my 530. ther's lots of info on this formum about Nikasil. To confirm this have it checked out by a bmw dealer or other shop. if you have less than 100,000 miles you may still qualify fora new engine, made of Alusil. some bmw dealers have a inventory of new blocks, i just priced one here in Houston, $3,800, just for the shortblock. good luck, if that's your probelm you have two options. 1) live with it, 2) replace the block. bob :(

I'm wondering why is this (Nikasil to blame) often the default? A Nicky block (if he in fact has one) doesn't just suddenly turn in the space of a few weeks. Like John and Jeff note, vacuum problems are generally the blame, especially as the pliability of plastic/foam is reduced with the colder temperatures...I as well would check the rear vacuum valve...it's in here in the archives under "M60 vacuum plate, etc..."

Cheers,
Duey

[632 Regal]

is to remove the oul filler cap when you start the car and also when its warm. The car should have a noticible change in idle quality when removed, if it doesnt then you have a big leak.

[javanic]

I'm having the same rough idling problems with my '95 540i (150K miles). In addition to what Ammo00 described, my check engine lights come on intermittently. While at the shop for transmission leak repair, the dealer told me the mechanic simply "reconnected" the O2 sensor to make the light go out. However, the light continues to come on. The stomp test told me 1213 last week and then today it came on again and the stomp test said 1222. Those are both Lambda control codes.

I'd like to know more about the vacuum leak tests and troubleshooting I've seen mentioned in this thread.

1) what is the pcv plate?
2) where are all the vacuum hoses?

Thanks,
javanic

[SharkmanBMW]

pcv plate covers the back of the intake manifold... it is about 5"x5" or so i think...

I have a manifold for sale cheap if anyone wants it!

[johnnyturbo2002]

car is in today getting the seals replaced and the vaccuum leak fixed ( I realize that isn't spelled right) anyway...sounds exactly what is happening to this one.

[Johntee540]

all this talk about vacuum leaks. My car is in for Tranny replacement. While it is there I am getting the Valve Cover Gasket Seals replaced. At the same time I decided (based on this thread) to have the PCV Plate changed as well. I may as well its gonna be open! - JT

[javanic]

Oh yeah. That carb cleaner spray test proved the vacuum leak for me. I tried it this morning. My 540 was "loping" grandly in the 29 degreeF temperature. I sprayed the carb cleaner on the intake side with no effect. Then I hit the PCV at the back of the engine and Vrrrooooom!

...Got my work cut out for me. Egad! I love this bimmer... :)

javanic
'95 540i 151k

[632 Regal]

just like looking the first time to see if I had Nikasil, just dont think I could forget about a leaky pcv plate.

[javanic]

just like looking the first time to see if I had Nikasil, just dont think I could forget about a leaky pcv plate.

Sounds like you've replaced a PCV plate at least once? I just started mine tonight. How in the world do I get the thing off? What's the sequence of steps to get clean lift-off of the intake manifold?

[540Dave]

Would the fact that this happens more when the cold weather starts indicate a bad ICV or would you continue to suspect vacuum leaks? My 95 540 is getting progressively worse as the weather remains cold and gets colder. In the warm weather it has ran flawlessly. Now it's stalling, the CEL is on and off. Idle is loping and rough sometimes then it will be smooth for a bit too. I don't want to buy a new ICV if the problem is vac based. I'm stumped too.

[632 Regal]

http://www.bimmer.info/forum/showthread.php?t=15671

[540Dave]

I just had a similar problem. The car is @ my local indy garage undergoing the search for an elusive vacuum leak. Sometimes you just hafta take it in.

[zhandax]

I both hate to resurect an old thread and hate to open a new one for a simple question. What is the name in 'on-line parts-place terminology' for a PCV plate? I have not located one from the site where I get most of my parts (buybimmerparts.com). I am a firm believer in replacing all the vacuum-associated rubber when first buying a 10+yr old car.

[632 Regal]

no problem, its not on that site at all. did you try calling BMA? All you have to do is ask for the part and theyll know what your talking about.

[MBXB]

1 PCV Plate 11617501562
1 Cap 11611747085
1 Rear Gasket 11611729728
1 Front Gasket 11611729727
4 Manifold Gaskets 11611433328

Most parts are available at BMA. Confirm the part numbers with your VIN number.




I both hate to resurect an old thread and hate to open a new one for a simple question. What is the name in 'on-line parts-place terminology' for a PCV plate? I have not located one from the site where I get most of my parts (buybimmerparts.com). I am a firm believer in replacing all the vacuum-associated rubber when first buying a 10+yr old car.

[mattyb]

yeh , definately nikasil. the pope rang me last night and asked about the declining influence of christianity, morality and the rapid incline in poverty and the social -economic ramifications of global capitalism in general as he was lost for an explanation and had asked god and he didnt know either. i asked him if he had a nikasil block in the pope-mobile and sure as sheep **** after taking it to the BMW stealer in the vatican he told me he has a nikasil block.pope john paul 11 put to many miles on it and now he cant get a replacement under warranty. so there u go all problems, even global world crisis typres are caused by nikasil! wtf

[zhandax]

Since the pope has not blessed nor replaced my intake gaskets, I must offer thanks for the part numbers! Even the site I mentioned has the parts when I search by part number. Is BMA the way to go for bimmer parts? I used to get parts from JAC enterprises in Torrence for several years, but he seemed to grow tired of shipping parts. Rusty's speciality is Mercedes parts, although he can get BMW parts and I have had him send me some for the old E28.

[Nikasilaholic]

Had all the same symptoms as everyone else here. Car would idle in the morning around 500 RPMs and sounded like it was going to die. OMG, it must be the NIKASIL problem! The sky if falling, the sky is falling!

Pulled the cover off the engine and tightened up both throttle cables which are attached to the butterfly valve on the throttle body. Take care and only tighten enough to open the valve slightly (you can see the bracket move as you tighten the throttle cables). Car now idles in the morning at 1000 RPMs and sounds like a new car. For some reason, my hot start problem went away as well. After the engine has warmed up, the absolute base idle of the car is now 800-850 RPMS.

[632 Regal]

umm...the engines supposed to idle at 500...lol

you bandaided something

haha...sorry ;)

Had all the same symptoms as everyone else here. Car would idle in the morning around 500 RPMs and sounded like it was going to die. OMG, it must be the NIKASIL problem! The sky if falling, the sky is falling!

Pulled the cover off the engine and tightened up both throttle cables which are attached to the butterfly valve on the throttle body. Take care and only tighten enough to open the valve slightly (you can see the bracket move as you tighten the throttle cables). Car now idles in the morning at 1000 RPMs and sounds like a new car. For some reason, my hot start problem went away as well. After the engine has warmed up, the absolute base idle of the car is now 800-850 RPMS.

[Beez540]

1 PCV Plate 11617501562
1 Cap 11611747085
1 Rear Gasket 11611729728
1 Front Gasket 11611729727
4 Manifold Gaskets 11611433328

Most parts are available at BMA. Confirm the part numbers with your VIN number.


ding ding ding... we have a winner. Nice work.:)


I'd like to note something about the 540 idle though. Sometimes simple things like changing the oil, changing the plugs, or just burning out some carbon can improve it quite a bit.

Mine seemed to be developing a slightly bumpy idles around the end of october when it started getting really cold. Changing the oil didn't help a whole lot, but when I put 1200 freeways miles on the sucker driving to the folks house and back for Christmas... it's idled perfect since then. And it's been colder since the peak of my problem.

[fast5]

hey i'm new here so i don't want to step on anyone's toes, but if it smooths out at running temp it could be the intake manifold gasket. that's waht it was on my car.