MP3 turbo idle problems!
 

Alright I have been battling this damn idle issue for severa months now. It all started after my turbo install.

Basicly the cars idle when the clutch is pressed in even while driving slow can fall to almost 0 RPM. If I am going 60 and I press and hold the clutch the RPMs will fall to 0 then return up to 800. If I accelerate then immedatly press in the clutch, the car will stall then a second later restart itself. Also the idle is the worst when the head lights are on. When switched on they can drop the idle to about 200 RPM.

So far I have confirmed there are no intake leaks by spraying choke cleaner on all joints, welds and connections after the maf and all over the intercooler to ensure no leaks. I have released the idle screw so far that it is all but come out.
THe VAC on the car is 20-21 PSI is great according to both Flyin miata and BEGI and rules out the possibility of a vacuum leak.
The idle fuel pressure is 35 PSI which is within range.

HELP!!!!!!!!!!!!!!

can be

-ignition system problem
-dirty or stuck IAC
-vacuum leak
-fuel system problem

Since the Vac is 20-21 doesn't that rule out the vac leak?

Where do I begin to determin if the others are the cuase?

yes it does... if it was steady

I would check the IAC first

Does the car run fine otherwise? Have you checked the OBD-II for codes?

If the answers are (1) yes and (2) there are none, my money is on the IAC (Idle Air Control valve, if you didn't already know that). :) It's the big electric-motor shaped thing on top of the throttle body; it will have a vacuum hose leading to the intake manifold.

FSM procedures for checking the IAC:
(1) Warm the car up to normal operating temperature. Unplug electrical connector to IAC. Engine should immediately stall or idle rpms should drop almost to zero (kinda like what your car does with the IAC plugged in). :rolleyes: If engine rpm increases or does not change much, proceed to step 2. [I betcha that unplugging your IAC makes little or no difference.]
(2) Unplug negative battery cable and IAC. Measure the resistance between the 2 eletrical terminals on the IAC. Resistance should be 7.7-9.3 ohms at room temperature. If not as specified, replace IAC.
(3) If step 2 checks out OK, inspect for open or short circuit between the IAC harness connector and terminals 54 and 83 on the ECU.

Good luck! :D

Thanks for the help so far guys, I will do all that was advised tomarrow morining.

2 questions.

1. Where exactly is the IAC sensor? Is that at the top of the throatle body, since there are several clips on that damn thing? Does anything distiquish it?

2. If I inspect the AIC terminals to the ECU shouldn't each pin show a short circuit, AKA direct connection, to at least one of the ECU pins? I would assume its an open circuit or a short to ground that would be a problem?

Sorry to continue to prod but I am not fmilair under the hood of this car as I should be.

I pulled the grey clip and nothing happened. It just kept going. I also checked the impedance of the valve and of the grey clip. The grey clip was 11.49 volts dc and the valve was 9.0 volts dc.
I had let the engine warm for about 10 minutes before doing anything but it is 30 degrees out so I don't know if that was long enough.

I took the cylinder part of the IAC valve off and it was covered with black seposites.

I didn't take the peice off the trottle body but I did notice it also had alot of black deposites.

After reinstilation and computer reset the car would not even idle at first and just stalled. I had to hold the gas down and let it rev for 5 minutes then it was able to hold itself. It still idles low and will al but stall if the lights are turned on.

I also check the charging voltage and its at 15 volts, aftermarket alternator, so that OK too.

Courtesy of a little creative thread searching:

To the immediate left of the "Injen" logo in this picture:
http://www.surfergeek.net/protege5/i...take%2019.html

Top dead center of this picture, partially cut off by the edge of the frame. The gray connector at right is the one to unplug to test the IAC:
http://www.surfergeek.net/protege5/i...take%2014.html

Got it? :bt:

You should double check what you're measuring. Resistance is measured in ohms, not volts (the little horseshoe-shaped sign, for the electrically impaired.). :) If you've got an old-school analog multitester, you may be reading the wrong scale on the meter face.

After hearing your description of the problem, if you unplugged the right connector I am almost certain it's the IAC. My car immediatly stalls when I unplug it. If the car's idle behavior doesn't change, the IAC *must* be broken.

Re: MP3 turbo idle problems!
 

I feel ya brotha!! I've got the same exact problem... It's your blow off valve... close that thing and you won't have much of a problem. Me? I deal with it and open it as little as possible. Let me know if you come across another solution! :D

So, what's the verdict?

I do remember replacing my BOV after the side port came completely off and the idle got better for a time being. Hmmm....could history be repeating for me...

That would be the clip I removed not to mentionen the cylinder I removed to clean.

I am all but certain I checked impedance (ohms) but I have been gone for a week so I will double check tonight. Hopefully It was just a typo, if not there isn't much of an excuse for me to have made that mess up.

I didn't upgrade to the FM blow off valve, I have the recirculating one that came with the kit but I will check it. I assume just blow on it and make sure it moves as it should?