89 535I rough idle

[70383roadrunner]

Is this make known for rough idle? I have 90K on my car. I bought it at 60K had it into BMW for valve adjustment and they told me that it is a fine line between smoothness and performance. If you want it to run smooth you sacrifice performance and vice versa. Does this sound right? And god forbid if you feather the gas pedal when it is cold it feels like it is missing but a couple minutes later the miss is gone. Any suggestions. I have new plug wires, plugs,valve adjustment,dist cap and rotor.

[wingman]

If it has a standard cam it should be smoothe. Sounds like the stealer can't fix it so they crap to you. Check for vacuum leaks as this is a common casue of rough idle.

[rob101]

Is this make known for rough idle? I have 90K on my car. I bought it at 60K had it into BMW for valve adjustment and they told me that it is a fine line between smoothness and performance. If you want it to run smooth you sacrifice performance and vice versa. Does this sound right? And god forbid if you feather the gas pedal when it is cold it feels like it is missing but a couple minutes later the miss is gone. Any suggestions. I have new plug wires, plugs,valve adjustment,dist cap and rotor.
AIRFLOW METER, that is the common cause of hesitation off idle, and partial throttle. they get carbon buildup in the tracks of the variable resistor that is attached to the flappy door. make sure first that your flappy door isn't sticking, then having a search around for on the web, usually you remove the black seal on top of the AFM you can see the Innards of the resistor. there is a good page somewhere about "reconditioning" an AFM with pictures that will help you.... but right now i can't remember where it is

[Jeff N.]

...the valve lash setting. If you tighten up the valve lash to a very tight spec setting (ie: .012), the car will tend to idle a bit rougher than if you open them up just a tad further (.013 or .014).

The lash setting has a small but noticable effect on the valve timing and is akin to advancing or retarding your cam. A tight lash setting opens the intake and exhaust valves earlier which tends to cause a slightly rougher idle. Early opening of the valves is the same as cam advance which is a tactic to increase low end power at the expense of upper rpm power.

Opening up the lash has the opposite effect.

I would be surprised if you could feel the difference.

(I think my theory is solid here, have to check Mr. A. Graham Bell for sure)

Jeff



Is this make known for rough idle? I have 90K on my car. I bought it at 60K had it into BMW for valve adjustment and they told me that it is a fine line between smoothness and performance. If you want it to run smooth you sacrifice performance and vice versa. Does this sound right? And god forbid if you feather the gas pedal when it is cold it feels like it is missing but a couple minutes later the miss is gone. Any suggestions. I have new plug wires, plugs,valve adjustment,dist cap and rotor.

[70383roadrunner]

...the valve lash setting. If you tighten up the valve lash to a very tight spec setting (ie: .012), the car will tend to idle a bit rougher than if you open them up just a tad further (.013 or .014).

The lash setting has a small but noticable effect on the valve timing and is akin to advancing or retarding your cam. A tight lash setting opens the intake and exhaust valves earlier which tends to cause a slightly rougher idle. Early opening of the valves is the same as cam advance which is a tactic to increase low end power at the expense of upper rpm power.

Opening up the lash has the opposite effect.

I would be surprised if you could feel the difference.

(I think my theory is solid here, have to check Mr. A. Graham Bell for sure)

Jeff

I think Jeff may be right. At least when I had the valve adjustment done by BMW and noticed the somewhat rough idle this is basically what the service manager told me with him not getting into the whole valve lash thing. Maybe when I have this done again I should have the valve lash looser. I know when they did it they said a couple were loose but another couple were very loose. They did check the idle control valve and said that was functioning correctly. I guess at this point in it's life I should change out the vacuum lines anyway and se what happends.