yes. moar high idle problems

[Oolop]

i have a 1986 325E bone stock m20b27

i have a high fluctuating idle problem (800-1800+) that i cant solve. tried searching but i couldnt find an answer to my exact prob. my TPS is fine, i dont know how to check my ICV (all the write ups i find are of the three prong sensor and mine is two) and i replaced all vacuum hoses, the elbow boot (MAP to throttle body) and even the charcoal canister hoses with the one-way valve in the middle, and all the other things you can think of.

i honestly feel like its the ICV but nothing happens when i adjust the screw or even unplug it. can anyone tell my how to check it electronically? when i checked for resistance i got 9.1 on mine and a used one i bought off someone who totalled their e30.

i read and did just what the pelicanparts.com troubleshooting article said. but to no prevail still.

HELP ME!!! i need my car back!!

[long tall eta]

take off the idle valve and spray it inside real good w/ carb cleaner till the fluid is no longer dirty. then shake it, you should hear it rattle inside. it might just be dirty. your car also has a icm ( green box in the glove compt next to the ecu) it's an idle control modual. could be that. i just had my high idle fixed although it wasn't fluxuating. it was a combination of the icv, tps and the maf all being slightly out of adjustment.

[Oolop]

yea thats the first thing i did, cleaned out the ICV and it barely helped.

i also got a hold of a spare ICM and ECU and plugged both of them in but still no fix :(

could it be my air flow sensor? what readings should i get when i check the prongs?

[lennon]

On a properly functioning m20, unplugging the ICV will make the idle jump up to about 2000rpm and then fluctuate. If unplugging your ICV does nothing, and it's already fluctuating like that, it sounds like your ICV is bad. Fairly common.

[MR.CHATO]

Try checking your o2 sensor. My eta had a similar problem not too long ago

[long tall eta]

On a properly functioning m20, unplugging the ICV will make the idle jump up to about 2000rpm and then fluctuate. If unplugging your ICV does nothing, and it's already fluctuating like that, it sounds like your ICV is bad. Fairly common.

^this, if you unplug your icv and it still remains the same, thats your problem.

[jlevie]

Idle or hard starting problems are most commonly caused by intake leaks and/or
a sticky or defective Idle Control Valve (ICV). The only reliable method of
locating intake leaks is to have a smoke test run on the intake and crank case
and to test the brake booster with a gage and vacuum pump. The complete list
of possible causes of an intake leak is:

Intake boot
Throttle body gasket
ICV hoses & connections
Brake booster, hoses, and connections
Crank case breather hose
Evaporative control hoses, valve, and expansion tank
Fuel pressure regulator & hose
Injector seals
Valve cover gaskets & bungs
Oil filler cap
Dip stick o-rings
Oil return tube o-rings

While leaks in some of those can be found by inspection or by spraying carb
cleaner on suspect areas, not finding leaks that way doesn't eliminate the
possibility. Only a smoke test will really work.

Once the possibility of intake leaks is eliminated, the ICV needs to be
removed and cleaned with carb cleaner until the vane inside moves freely. When
the ignition is switched on you should be able to feel vibration from the
ICV. If no vibration the ICV is bad, there's a problem with its wiring or
connector, there's a problem with the TPS, or the DME (or Idle Control Module
(ICM) on an ETA car) is faulty.

For the DME (or ICM) to control idle, the idle switch in the TPS must work
correctly. The switch should close when the throttle stop is 0.030-0.060" off
the idle stop screw.

The fuel system should be tested via the suite of tests in the Bentley manual
as invalid rail pressure can be a contributor to idle and starting problems. A
simple injector check is to pull the injectors, jumper the fuel relay to run
the pump, and see if the injectors are leaking. You can also point the
injectors into a towel, remove the coil wire, and crank the engine to see if
all of the injectors appear to be spraying in a similar fashion. The best
approach to possible injector problems is to have the injectors cleaned and
flow tested. Since raw fuel can or will be released in these tests, have a
fire extinguisher handy.

While a bad check valve in the high pressure pump can result in longer than
normal cranking, if the fuel system is working as it is supposed to the rail
will reach normal pressure in a few turns of the engine. A weak pump, clogged
filter or leaking FPR in conjunction with a failed check valve can result in
longer cranking.

The O2 sensor can be a contributor to idle problems. The O2 sensor is a
scheduled maintenance item with a useful life of no more than 100k. If the
sensor has that mileage or more (or is of unknown age), replace it.

The AFM can be a contributor. If the vane doesn't move freely or the
resistance track is worn the DME may be receiving invalid data from the
AFM. And if someone has fiddled with the bypass air adjustment the DME may be
unable to stabilize idle. The bypass air adjustment should only be adjusted
per the procedure in the Bentley and with an exhaust gas analyzer. And even
then everything else associated with engine management has to first be
operating properly. If the AFM becomes a suspect, replacement with a good used
unit is the best approach.

Improperly adjusted or malfunctioning valves will affect idle and starting. As
can compression issues from ring or cylinder wear. A valve adjustment is
called for every 15k. A useful diagnostic is to run compression (dry and wet)
and leak down tests on the engine. Aged ignition wires, plugs, distributor
cap, or rotor can cause problems. Insulation does break down with time and
heat. And since the youngest E30 is going on 20 years old, if the ignition
system is original or the plugs are old replacement is indicated.

Although not usually a problem, a bad DME temp sensor is a possibility. That
generally won't cause an unstable idle, but can cause hard cold or hard hot
starts and/or a rough idle. As can problems with the timing reference
sensors. Although not commonly encountered, a bad harmonic balancer on an
M20B25 or M30 engine will cause problems.

When all other possibilities have been eliminated and idle or starting
problems persist, replacement of the DME, or if applicable the ICM, is
indicated.

[Oolop]

ok, so it was the idle control valve afterall. well now i know lol :P hopefully this will help someone else in the future