Searching for answers about my idle

[gtdragon980]

After surfing the web for about a year, I have gotten no luck with my idle problem. The cars issue is that it idles at a constant 2k all the time. Sometimes it may go back down to 750 and sit there for a while but it usually comes right back up to 2k, merely ruining the fun of driving the car and damaging the clutch. I have already checked and cleaned the icv and there was no luck. I then unplugged it while it ran and made little to no difference in idle. Next I unplugged the afm and the idle went completely down to 750. So I did some research on afm adjustment and I went at it to test if it would help at all. When I made some small adjustments to the cog wheel inside, it magically went down! But like I said before my car tends to go back to normal idle and stay for a while and go right back up! Soo the afm adjustments made no difference and I put it back to it's original adjustment and left it like that. I don't think there is any vacuum leaks because I've sprayed tbc on every possible inlet of air and it made little to no difference in idle. What am I missing, I've been chasing my tail on this for so long with no improvement so anyone got any other ideas I could try?? TIA

[jlevie]

Spraying carb cleaner on parts of the intake only works it you happen to hit the leak with the fluid and if that point happens to be close to the head. A smoke test of the intake and crank case is far more reliable and will reveal any intake leaks. There are a number of places where you can have an intake leak (some of which aren't obvious):

Intake manifold gaskets
Throttle body gasket
Injector seals
Intake boot
Brake booster and/or lines
ICV connections
Evap control
Oil return tube seals
Dipstick O-rings
Oil filler cap seal
Valve cover gaskets

After finding and dealing with intake leaks you need to verify operation and adjustment of the TPS and operation of the ICV. If the AFM has been messed with, replace it with a good used unit. A sticking throttle body, miss-adjusted or sticking throttle cable, or a miss-adjusted idle stop can also be a cause. And if the car is an early production 325e, a bad idle Control Module is a possibility.

[lateracer]

I'm also trying to chase down the source of a high idle as well. Thanks for pointing out some less obvious places to look for leaks.

Can these be detected w/ a can of cleaner sprayed directly on them:

Intake manifold gaskets
Throttle body gasket
Injector seals
Intake boot
Brake booster and/or lines
ICV connections
Evap control
Oil return tube seals
Dipstick O-rings
Oil filler cap seal
Valve cover gaskets

or should I try something else. Would like to avoid guess/replace if possible.

[Court M3]

Same problem here. Will hae to tackle afm sometimes later though.

[jlevie]

Opps I forgot one; the breather hose from the valve cover to the throttle body.

Carb cleaner will work on the injector seals, throttle body gasket, brake booster connections, ICV connections, and sometimes on the intake gaskets and evap control valve. The problem with the latter two is in trying to get carb cleaner all around the possible leak locations. Carb cleaner pretty much won't work on any of the others. They are too far from the intake.

A smoke test isn't expensive, usually about an hour of shop time, and it will find any leak.

[ShortSkinnyKid]

I have already checked and cleaned the icv and there was no luck. I then unplugged it while it ran and made little to no difference in idle.

If you unplugged the ICV and there was no difference in the idle, that may be your problem. When you unplug it your idle should go haywire up and down. I would connect a known working ICV and see if the problem is corrected.

[gtdragon980]

thanks for the great info ill check that stuff out. As far as it being an idle issue, would an intake leak cause it to go up in revs? I was suspecting something along the lines of electricals..

Spraying carb cleaner on parts of the intake only works it you happen to hit the leak with the fluid and if that point happens to be close to the head. A smoke test of the intake and crank case is far more reliable and will reveal any intake leaks. There are a number of places where you can have an intake leak (some of which aren't obvious):

Intake manifold gaskets
Throttle body gasket
Injector seals
Intake boot
Brake booster and/or lines
ICV connections
Evap control
Oil return tube seals
Dipstick O-rings
Oil filler cap seal
Valve cover gaskets

After finding and dealing with intake leaks you need to verify operation and adjustment of the TPS and operation of the ICV. If the AFM has been messed with, replace it with a good used unit. A sticking throttle body, miss-adjusted or sticking throttle cable, or a miss-adjusted idle stop can also be a cause. And if the car is an early production 325e, a bad idle Control Module is a possibility.

[Naplm00]

thanks for the great info ill check that stuff out. As far as it being an idle issue, would an intake leak cause it to go up in revs? I was suspecting something along the lines of electricals..

Yes an intake leak will introduce unregulated, unmeasured air to the engine..leaning it out and causing a high idle.


I swapped and cleaned my ICV a few times trying to find a high idle. Then i swapped to "known good" components

and remade all of the vacume hoses with new hose and clamps, RTV on the aluminum push fit connectors in the side of the TB

Theni replaced the orings and seals on the valve cover and dipstick

I also replaced the intake boot and the rubber elbow that connects the ICV to the TB


after all that..idle is rock solid