Cold start system and wierd idle

[Helltime]

So i have been working on fixing ALOT of things on this car (85 325e) that the previous owners messed up or were just plain worn out, so i decided to trouble shoot and fix some of the smaller items i know will need attention.

I started by removing the air intake system from the TB, i was seeing if the TB needed cleaned and inspecting lines for cracks and such



Here is what i found in the big line that goes into the air boot itself


I was wondering what the hell that was doing in there, so i took it out to see what kind of difference it made if any, rpms shot up to 3k-3.5k upon start up and didn't drop, so i shut it down, tryed again and same result, i put the dime back in how i found it and it idled like it has been (around 900rpm). What is causing this? It looks like the cold start setup is bypassed as well, is that connected?

[Helltime]

Ok, i came across a thread saying it is a normal "fix" for high idle...i want to kno what the cause of the high idle is...not a half assed fix

[jlevie]

That is not a "normal fix" for a high idle, but rather a ghetto fix for repairable problems. Take out the coin and work your way through what is below (starting at the top) to fix the car the right way.

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.

[Helltime]

I am actually going to start with the ICV, because i tryed unplugging it (the wireing to it is a PO chop job and needs redone) and nothing happened, the car ran the exact same..so i don't think its working/getting power. Which color wire goes to which plug? I'm going to start there

[Helltime]

I tested the wires going to the ICV, No power going through either one, both wires all the way to the main harness appear to be in good shape, so what now?

[Quadrajet]

Either you have a dead ICV control module, or there is no signal to it. Sorry I can't give a better answer, my Bentley is out in the shop.

[Helltime]

Either you have a dead ICV control module, or there is no signal to it. Sorry I can't give a better answer, my Bentley is out in the shop.

I'm assuming that is that different from the actual valve then?

[wodcutr]

Your ICV module is under the dash by your ecu. It is a small green part with wires going to it. They do go bad and if bad, the idle is high and may hunt up and down big time. I have a good one if you need one.

[Helltime]

Your ICV module is under the dash by your ecu. It is a small green part with wires going to it. They do go bad and if bad, the idle is high and may hunt up and down big time. I have a good one if you need one.

Don't supposed you have a picture? not sure what it looks like, trying to find mine

[Helltime]

found the module, it was completely unplugged, i am getting power to the valve now

[Disco Benny]

Quick question...

I'm hunting a vacuum leak and cannot find HOWEVER, when I pinch the hose from my VC to Throttle Body my idle shoots up and stabilizes

WTF? do I need to the "Dime" trick too?

[jlevie]

You need to have a smoke test run to find the leaks.

[Disco Benny]

FOUND IT!

That spring loaded transfer tube from intake to bottom of engine was not set properly even though I replaced both o-rings with my HG and Cyl Head job...reseated and VOILA I now have a steady cold idle @ 800 and it drops...hells yeah

[Helltime]

Btw, never did update, after plugging in the module, taking the dime out and adjusting the valve, it now idles about where it should

[Davidov]

Btw, never did update, after plugging in the module, taking the dime out and adjusting the valve, it now idles about where it should

That's what these cars need, just some careful thinking and some patience.

Good job.