Rough Idle, Black Smoke.

[BMW BMXER]

Symptoms:
-Bumpy idle, sorta of sputtery puttering and shuddering
-Idle goes up and down
-Slight Black smoke on idle (will check to see if during accel too just need my dad to hold the gas)
-ICV screw all the way out idle doesnt go up and down but it idles like shit
-ICV screw midway to down idle goes up and down to almost the point of stalling, never really settles.

Possible Related issues:
-Sudden temp change
-Exhaust leak right after the manifold and before the muffler
-325 ish thousand miles

Possible fixes I have thought of
-Hit ICV with hammer
-Hit ICV with bigger hammer
-Shoot ICV
-Buy new one
-Your suggestions?

[EtaSport]

Hard to say. Mine did the same thing and wasnt related to the icv in any way. All I know is that its either getting a WOT signal and dumping fuel in that it can't burn, or its getting the right signal but not getting a strong enough spark to burn it off. I replaced my coil, wires, and distributor cap and my problem went away. Other things to check:

TPS, and setting
AFM
maybe swap ICV
Fuel filter
Fuel pump
Cold start injector
Coolant sensors
Fuel injectors
ECU
ICM

unfortunately, and im sure you know, these things dont tell you too much. It seems like all m20 problems have identical symptoms and completely different remedies. I would still look into the ignition however. Check to see if you have a strong/regular spark on your plugs. They are probably carbon fouled as well, so I'd buy some new ones and check the new one. Good luck, hope some of this helps.

[nando]

not a solution, but a clue. black smoke usually indicates a rich condition. you should be able to smell it out of the exhaust.. if you don't know what a rich mixture smells like, go stand behind a carb'd chevy and you'll know really quick. :)

read your plugs too, it's easy and you'll be able to confirm the above.

and make sure you test the TPS. my car has an exhaust leak right after the manifolds as well (there's a crack) but that shouldn't affect your idle since the O2 sensor is ignored when you're idling.

[BMW BMXER]

The plugs are about 6 months old.
Fuel Filter is about 6 months old.

I cleaned the icv with some shit called xlylene that my dad said "should so the trick" the idle isn't lumpy anymore but still loopy. No more smoke.

Car does run rich though.

How do I check the tps?

[EtaSport]

When you open the throttle plate on the throttle body you should hear a click when the butterfly is open. If you do not hear the click then you need to loosen the screws on the TPS and turn it until you can hear the click. I think it only has two signals, closed for idle, and open for WOT. Other than that, id just say clean everything, maybe try some fuel injector cleaner, or fuel treatment, and again check for any leaks.

[BMW BMXER]

Thanks I will check that out.

How does an ICV work exactly? I know there seems to be a motor or something that spins around in it that does... something. But I don't know what?

Can anyone shed some light on the subject?

[DaN]

Have you checked the fuel pressure regulator?, Whats your fuel pressure?

[EtaSport]

Have you checked the fuel pressure regulator?, Whats your fuel pressure?

oh yea, forgot about that, shame on me.

pretaining to the ICV~Not sure how the thing works. I read somewhere that there was even an electric wire inside of it (or similiar) that reads changes in air flow and sends signals. The way I read it, it works much like a mas air flow meter. The rest I know is that it lets unmetered air into the intake, and how much is controled by the screw. Someone is bound to know. Im curious myself.

[DaN]

Whatt???
The fuel pressure regulator is mounted on the end of the fuel rail, it regulates the pressure in the rail. If its stuck closed then pressure will be to high, each time the injectors open too much fuel will be injected.

You are refering to the air flow meter, all the air that goes into the engine is routed through this device which has a door that changes position with flow.Mounted on the door is a potentiometer, resistance varies with flow. The computer takes this info and makes calculations for injector pulse width, ignition timing, etc.

[EtaSport]

Oh, I wasnt talking about the fuel pressure regulator, I was trying to answer his question about the ICV

[kowalski]

The plugs are about 6 months old.
Fuel Filter is about 6 months old.

I cleaned the icv with some shit called xlylene that my dad said "should so the trick" the idle isn't lumpy anymore but still loopy. No more smoke.

Car does run rich though.

How do I check the tps?

by reading the plugs he meant
black is rich
brown is normal
grey is lean

[rwh11385]

update?

[BMW BMXER]

Oh right, I fixed my exhaust, cleaned my plugs, replaced my air filiter with a K&N, cleaned and adjusted my ICV multiple times, got a chip and started running better gas and the weather got a lot better.

Any combination of these has since fixed my problem.

[arnoldgtr]

The ICV regulates the amount of air that bypasses the throttle. More air means a higher idle speed.
The ICV is a solenoid, or linear motor. It has a coil of wire which creates a magnetic field, moving the plunger.
The early 2-wire VDO ICV's are single pole. They have a spring which holds the plunger open. When current is applied to the terminals, the ICV closes.
The later Bosch 3-wire ICV's are two-pole. There are two coils of wire. The normal position is half-open. Current applied to one coil will open it further. Current applied to the other coil will close it fully.
The later design is superior because if it fails electrically it is in a fairly 'normal' idle position. With the early VDO ICV, electrical failure means the ICV will be wide open, causing the 2000+ RPM idle situation.
The two ICV designs are not compatable. The VDO ICV is controlled by a separate control unit. The Bosch ICV is controlled by the Motronic unit (ECU).

[KenC]

I cleaned the icv with some shit called xlylene that my dad said "should so the trick" the idle isn't lumpy anymore but still loopy.

It's actually "xylene". I hope you wore gloves and didn't breathe the fumes. It's what the English call a "carcinogen." (Just as nearly all benzene derivatives are).

But anyhoo... glad you got your prob fixed. What do you think it was that fixed it?

My idle isn't really all that stable... but I've yet to encounter an M10 with a perfect idle...