Rough Idle

[Mike B.]

My newly installed M50 has a bit of a rough idle. It idles around 600-650 and is pretty buzy, is this typical? If I give it enough gas to get it up to 850-900, it is really smooth.

I've checked for vacuum leaks and everything is sealed up tight. Any thoughts on whether or not is could be the ICV or the O2 sensor?

[Jason89i]

My newly installed M50 has a bit of a rough idle. It idles around 600-650 and is pretty buzy, is this typical? If I give it enough gas to get it up to 850-900, it is really smooth.

I've checked for vacuum leaks and everything is sealed up tight. Any thoughts on whether or not is could be the ICV or the O2 sensor?

check your engine temp / coolant temp sensors (the two right next to each other under intake.) if you mix them up (not too uncommon) then you will get really rough startup. also, check the green wire coming off the o2 relay (its the preheat element.) it should be getting 12v. what is your vacuum reading? check for the small (1/8" diam) rubber hose coming off the bottom of intake manifold (next to the air temp sensor). alot of people forget to put that back on. or, yes, it could be the idle stab valve. reach down and feel if its buzzing. if not, check for voltage / ground.

cheers, jason

[Mike B.]

The temp (engine/coolant) are correct.

I have two green wires coming out of the O2 sensor relay. The first is a thinner guage (20?) green/brown wire that is 12v when switched and the other is a thicker guage (14?) green/violet wire that is 0v when switched. Which wire should I be checking?

[Jason89i]

The temp (engine/coolant) are correct.

I have two green wires coming out of the O2 sensor relay. The first is a thinner guage (20?) green/brown wire that is 12v when switched and the other is a thicker guage (14?) green/violet wire that is 0v when switched. Which wire should I be checking?

whoops, your looking at the fuel pump relay.

the o2 relay should have a brn/grn, red/wht, red/wht and grn/blu (or more commonly just grn.)

edit:
brn/green is the switched ground from the ecu that triggers the heater.
red/white is the power (switched when "on" power from the main relay.)
green powers the heating element from the o2 relay.

cheers, jason

[Mike B.]

Yep, looking at the wrong relay...

If it was the O2 sensor heating element, the idle would improve when the exhaust heats the sensor, correct?

[Jason89i]

Yep, looking at the wrong relay...

If it was the O2 sensor heating element, the idle would improve when the exhaust heats the sensor, correct?

yes and no. it would get better, however...... the car runs in open loop when first started. the ecu does not read the o2 sensor until after about 20 sec's. the o2 sensor is calibrated to read exhaust between 500 and 600deg (dont quote me that was from memory) but rarely does the exhaust heat the o2 sensor that much. so, the 02 heater (powered by that green wire) heats an element up in the o2 sensor for the correct reading.

cheers, jason

[equate975]

Also, did you plug the hole where the evap purge valve would go on the bottom of the TB?

[Mike B.]

All ports on the TB are plugged or being used.

I checked the wires coming out of the relay, when the ignition is switched, I get 12v on the brown/green wire and 0v on the green/blue wire. So apparently, I'm not getting power to the heating element, correct?

[cheades]

Did you clean the idle control valve, they like to get dirty and don't allow the mechanism to turn easily so the car will idle rough.

[Mike B.]

I have not cleaned the ICV. By the looks of it, the intake has to come off to access it. I guess this falls under "Things to do when the engine is out of the car" list. ;)

[cheades]

If you have any young kids (10-15) or know of some hire them for $20 to pull it out with their small arms/hands. It is accessible by removing the intake boot and you should be able to pull it out without too much trouble.

[Mike B.]

I checked the wires coming out of the relay, when the ignition is switched, I get 12v on the brown/green wire and 0v on the green/blue wire. So apparently, I'm not getting power to the heating element, correct?

With the engine running, I get 12v on the brown/green wire and 0.2v on the green/blue wire. Both red/wht wires have 12v switched/run. So I think I have issues with the O2 heater. Now, how do I fix this? I tried a new relay - same results.

This isn't a seriously rough idle, just a bit rough and low (550-600 rpm). The engine isn't close to stalling, but the whole car shakes sitting at a light and is a bit annoying. This occurs when the engine is both cold and warmed up.

I was able to remove the ICV and clean it with Throttle Body cleaner - no difference.

[Mike B.]

Well, I've tracked down my vibration to the aluminum cups that I have mounted over the 320i transmission mounts. They are adding a LOT of vibration to the cabin.

Can I get away with removing the cups, or will I get too much movement of the drivetrain without them?

[Jason89i]

Well, I've tracked down my vibration to the aluminum cups that I have mounted over the 320i transmission mounts. They are adding a LOT of vibration to the cabin.

Can I get away with removing the cups, or will I get too much movement of the drivetrain without them?

ive tracked my cars with and without the alum caps. with=no torn motor mounts. without=50/50 chance in my experience. car had the 533/washer mounts and those started to tear. my current car does not have them, but i used the larger round rubber mounts (in lieu of the hourglass ones) and they have not posed any problems.

i emailed you re: 02 preheat and idle. it didnt seem to help much with idle (on the 5-6 cars) but it really smooths out the engine.

jason

[Mike B.]

I have the large, round rubber mounts as well. I think I'll ditch the cups and see how much it helps with the vibration.