CEL & Cold Idle Problems

[88SuperETABD]

Recently added a Miller MAF/WAR Chip and having cold idling issues, but other than that and the CEL it runs PERFECTLY.

CEL and Cold Idle Problems:
So I tested the MAF and its getting proper readings and voltage, so I know it is not the problem, the car runs excellent (better than ever) when warm, during cold idle tho, it wants to idle at 5-600 rpm's poorly. When warm, idles perfectly around 750-800. CEL is on and throwing the 1215 Code...

"Code 1215 - Indicates problem relating to Air / Mass Flow Meter - AFM or MAF depending on your e30 model. Causes could be cable wire damage, short circuit in the unit, or air / vacuum leak (check air intake hose - big L-shaped one)"

Funny thing was last night I drove my car HARD on Hwy 9, and the CEL shut off. The car was running awesome, before and after the CEL was on (once warmed up). But today when i started my car CEL popped back on and poor cold idle remained until the O2 sensor kicked in.

Brody @ Miller was helping me diagnose what's going on, and we haven't ruled out the TPS completely, and he told me the ICV should be pretty loose. He says you should be able to hear it open/close by shaking the ICV as you would a doorknob, and I think mines a little sticky because I have to give it kind of a harder shake to hear it. So I blasted the hell out of the ICV with some carb cleaner for a second time, It looks spic n span in there, but it still doesn't shake as loose as I think it should. Can someone confirm this?

Any ideas would be greatly appreciated. Although my car runs better than ever other than the cold idle (2-3 mins) and throws the 1215 CEL code, I want these 2 problems gone.

P.S.
The Miller MAF/WAR is a must for m20's I think...and I have a feeling this problem has nothing to do with the MAF install, but may be just a little more evident than before, because before the Miller MAF/WAR, my idle was crap as well, but always. Now its at least great when its warm, only only crap when the engines cold.

[88SuperETABD]

Also in the bentley it claims the TPS should be getting "Atleast 5 Volts" mine is getting around the high 10 volts (10.8ish IIRC). Could that be a problem?

[jlevie]

If you were having idle problems before the MAF/WAR install, the odds are that those problems are still present. Other than the AFM possibilities, start at the top of the list below and work your way down without skipping anything.


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.

[88SuperETABD]

Thanks, I'll go through this list, seems as tho these are for problem starting, my car cranks and starts up normally. And when I say it had problems idling before, I'd say it just wasn't smooth, but could be just from my cam. Also, the idle problem is only on cold idling, once warmed up, it runs flawlessly, I'm thinking it has to do with some hardware for cold idling. Which I believe rules out the o2 because the o2 isn't used at first startup to my understanding.