When engine is cold, drain all of the coolant in the radiator into a clean container (or buy new coolant if you are due for a change).

Open the bleeder valve on the thermostat housing. Fill the radiator. When air stops spitting out of the bleeder valve and a steady stream of coolant comes out, close the bleeder valve. Top off the radiator.

Reset the ECU by pulling the radio/backup fuse. See if your problem gets fixed.

 

IACV tests

1) When I pulled the IACV wire the RPM's went from 2000 to 1200 and stayed there. Since it didn't go down to the base idle of 550, is the IACV not closing completely? This test is unrelated to "air in coolant", right?

2) When I put tape over the IACV bypass port in the throttle bore, no matter how long I idled or how high I revved the engine, the needled always settled at 750 RPM's.

Is this problem IACV related?


Coolant

Radiator is full and reservoir level is normal
Hoses do not "slosh" when I squeeze them
Temp gauge needle runs up 1/4 from the bottom as expected
Heater puts out heat


I will burp the coolant just to make sure.

 

The idle stablizing w/ the bypass inlet covered suggests that the IACV is sticking; open or partially open. IACV is a spring-close, power-open valve, and is rapidly cycled open/close... by the ECU to stablize idle at preset values; higher for cold temps and lower for fully warm.

Suggest removing the IACV completely (disconnect coolant lines necessary) and attempt to clean and restore the correct valve movement. Check valve movement w/ a power supply for correct action. If you can't restore correct movement, then replace IACV.

good luck

 

Will give it a try.

What kind of power should I hook the IACV up to in order to test it without burning it up?

Could I just unbolt the IACV, keep the electrical connector hooked up, and see if there is movement when I turn the ignition key?

 

IACV uses 12V. I would check for 12V to the connector on harness side.

You need to carefully clean and check the valve movement. It may be possible to do in place, but position of the IACV on backside of throttle body makes this difficult. Your symptoms suggest the valve is sticking in open or partially open position.

good luck

 

I removed the IACV and hooked it up to a 9 volt "smoke alarm type" battery. I was able to get a "click" and see a barely perceptable movement (1/32"). What kind of movement am I looking for here? 1/8", 1/4", 1/2"? I cleaned it again, and put it back in, but the problem persists. When tested, it looked like it might not be seating completely, but the movement of the "plunger" was barely noticeable so I can't really say. Maybe 9 volts isn't enough.

Also, when I cleaned my FITV, I was able screw it in 2-1/2 turns. I see that there is some debate about whether to screw it in tight or leave it a little loose. The car has 333K on it if that matters. If I unscrew the FITV would that tend to help things, or would it be better to leave it tight and just readjust my base idle?

 

The suggestions is to tighten the FITV until it is snug.

Before you change the base idle, remove the air intake duct from the TB. Start the car and allow it to warm up.

Covering the bottom port with your finger should have very little vacuum and have little change in the idle.

Covering the upper and lower port should cause the car to stall out.

Let us know what you find.

 

That voltage may be too low to fully engergize. You must overcome a spring to fully open. I don't know the valve movement range, but would suspect 1/4-3/8 inch. What you want to check is for the spring return action. It could be the return spring is broken or movement is binding somehow.

good luck

 

I warmed it up and put my finger over the FITV port and there was a noticeable suction without any change in RPMs. I then added my second finger over the IACV port which had a great deal of suction and the combined effect caused an immediate stall.

I will keep the FITV screwed in tight and I will forego resetting the base idle for now since the initlal warmup always settles down nicely at 750. It's that later "hot soak" warmup that makes the idle stick around 2000.

The broken or worn out spring in the IACV makes sense. There might be some intermittent nature to this, but I think I am beyond cleaning or repair at this point. Even if there was air in the coolant, pulling the 2P connector on the IACV and only dropping to 1200 proves there is an "IACV related" problem.

Does the amount of voltage that the ECU sends to the IACV vary? Is it possible that the "plunger" in the IACV doesn't close tightly because it is receiving slightly more than 0 volts?

The reason I ask this is because when the car was really warmed up and exhibiting the "stuck 2000 RPM" problem, I turned it off, disconnected the 2P connector, and stuck my voltmeter leads into the female part of the connector. When I turned the ignition key to the first position I got a reading of 1.8 volts. As warmed up as it was, I would have hoped for a reading of 0. Is there any validity to my test?

Also, where is the ground for the ECU located?

Thanks for the help.

 

It gets 12v but intermittently. So your measurement depends on your voltmeter.

It very quickly switches 12v on & off, kinda like buzzing. If it's on 5% & off 95% then you'll think you're measuring a small voltage. (I'll assume you aren't using an oscilloscope...)

A better test would be to back-probe that wire while the engine is idling. Especially if it's idling high. By turning it off to disconnect the wire, you aren't measuring what it was actually doing when running.

On second thought...
Since that wiring is in the engine compartment maybe back-probing isn't good - you don't want to pierce the insulation & allow corrosion in the future. Make up jumper wires so you can connect the wires to the IACV along with a place to stick your voltmeter probe. The idea is you want to measure it WHILE it's screwing up with the engine running.