Low/no idle with CEL for IACV low voltage

[Foment_life]

I'm having some trouble that I'm not seeing any particular write ups about, hoping you good folks can help.

My CEL is indicating low voltage to the IACV, and I'm experiencing a rough idle/no idle at almost all stops.

I had this happen about a month ago and after cleaning what I am lead to believe is the IACV (drivers side 2 bolts right next to the air box) cleaning the connections, smearing some dielectric grease on the connector, dropping some dry gas in the tank and filling up, it got better without any indications of the problem returning.

Many of the mechanics or mechanically inclined I spoke with feel that it was likely bad gas at that time, but the problem is reappearing now and is going to make the drive to/from work quite the hassle.

I've got an '01 Outback sedan with an automatic transmission and the 2.5 litre 4 cylinder engine.

I'm open to any ideas anyone has, preferably without replacing the 200-400 dollar part.

If anyone can point to a guide for this, pref with the same engine and some pictures that'd be most helpful.

I'm going to run to Wal-mart and get some Sta-Bil and intake cleaner today, if anyone has any suggestions, I'm all ears.

Thanks in Advance!

[Brucey]

What's the exact CEL? P1440?

[Foment_life]

I believe it was P1510, but I'll need to hit it with the reader again when I get home.

Any thoughts?

[ETC]

Check the connection/ wires at the IACV.

Try spraying some cleaner through the Hole in the inside of throttle body before the throttle plate.

If that doesn't do it ... Pull the valve off again and clean it really well. Spray cleaner through the hole it goes in to and make sure the whole thing is really clean. It worked before, maybe it just wasn't clean enough and some dirt got in there and is sticking it up again.

It isn't idling because that valve is what lets air in the motor during idle while the throttle plate is closed.

[Foment_life]

ETC: I pulled everything apart today, sprayed off the connections with electrical cleaner, and coated them with dielectric grease, somewhat unintentionally disassembled the IACV, sprayed the whole thing down with carb cleaner, took off the air box, sprayed down the throttle plate, opened it and sprayed a good bit down in there, and wiped it all down with paper towels. I'm getting an idle again, but it's very low < 500rpms and a little rough. how hard should the IACV move exactly?

Brucey: as per your suggestion yesterday I dumped some fuel stabilizer into the tank, and I connected the green relays below the dash and checked, it is clicking, but it's not a terrifically strong feeling click. You wouldn't really be able to hear it over the fans and other clicks, but you can feel it with your hand on the IACV.

I have noticed a small crack (but no leak) in the hose running from the fuel filter, so I have not been able to replace that yet, I need to pick up a new pair of hoses for it first. How much bearing would this have on things? It's not leaking, but I wouldn't be totally shocked if it is causing a loss of vacuum at idle.

I have had some trouble with the positive terminal on my battery corroding, but it has never had any bearing on anything aside from occasionally needing to be cleaned, could this make an otherwise minor problem much worse?

[ETC]

That's a little low but, you may have some extenuating factors.

You can check for intake leaks with a can of cleaner. With the car idling, spray sort bursts at any suspected leak sites ... if the car revs or stalls [depending on the volatility of the spray] you have a leak. Have a fire extinguisher handy and and you may want to mist the engine [idling] with a misting spray bottle of water at night to look for ignition wire/coil arcing before you start spraying anything flammable at the motor. The misted water may cause the engine to stumble if you have a vacuum leak so, two birds with one stone right :]

Clean the PCV valve as well since that can be a source of intake leak. It sucks vapor from the crankcase and, if it sticks open, can cause problems.

Also check the valve covers and spark plug wells for oil leaks and, if you havn't tuned it up for awhile [or ever] might want to replace those plugs and possibly wires anyway.

If the positive terminal has corroded in the past, check the wire itself for corrosion and check the other end for corrosion. Check the grounds as well. Bad electrical connections can cause all sorts of issues and, on a modern car, everything is controlled by the ECU and Sensors so, make sure that's all clean and the wires are in good condition. If you flex the wire and green stuff falls out, replace the wire, it will only get worse.

[Foment_life]

Thanks ETC, I'll take a look into all of that this weekend. The wire seems to be okay, it's just the very thin stock clamp that doesn't seem to want to stay free of corrosion. I have cleaned it to the best of my abilities and coated the terminal in dielectric grease, hoping that that would help some but the clamp has corroded enough to have lost a bit of grip, though this hasn't had an effect on starting the car.

This weekend I was already planning to do plugs and wires, replace the hoses to and from the fuel filter, and attempt to further clean the IACV and adjust the idle, but I'll add the PCV to the list and I'll cut the lights in the garage and grab a spray bottle I s'pose.

As an update, the car will not idle while it's cold, but does idle (surprisingly comfortably) at about 200-250rpms once it's warm. This only seems to be the case in park, once the car is in gear, it will stall every time if I don't keep the accelerator depressed a bit.

Anything else anyone can think of to check this weekend?

[ETC]

Oh, I thought it was more like 500 ... yeah, that's low.

CEL on ?

You can't really adjust the idle, that's what the IACV is for, it's activated by the ECU and should be essentially "wide open" at start up.

Try blowing throttle body cleaner through the holes both ways when you have the IACV out, if it goes both ways without restriction and the the valve is clean and has good electrical connection and since modulating the throttle seems to "solve" the issue, your IACV may not be functioning correctly.

I know that's not much help but, since I havn't actually done any troubleshooting on that part, I'm not sure what to suggest.

Personally I would probably pull the part out, hook it back up, turn the ignition on and see if and how much it moves. All speculation on my part since it havn't done it.

Do you happen to have any "really good friends" with a same generation Outback ? Nothing like swapping out a known good part to see if that's the problem.

[Foment_life]

I've got a buddy with a 2.5L Legacy sedan, also auto, if anyone can verify that it's the same engine I can check w/ him to take a look at his.

The IACV on the auto isn't what you'd think of regarding an IACV, typically they have the 2 or 3 small reservoirs, almost like the bottom 1/2 of a carburetor correct? The auto has what appears to be a small electric motor that will move a screw with a plunger on the end to block what I have to assume is small inlet for air. I can take a few pictures of the part out of the car today/tomorrow and post them, maybe someone can point me to a few other alternatives then.

It appears that the IACV is functioning, but not to its fullest capacity, possibly has some debris lodged in the back of it near the small electrical motor causing it to have trouble opening fully?

The CEL is on, pulling a code for low voltage to the IACV last I checked it. I want to trace the connector back to its origin(s) and clean those connections as well.

I'll pull the IACV later today and see what kind of reaction it has when not in the intake.

[ron917]

The service manual should have an resistance value for the IACV (I don't have a manual for your year, else I would look it up). Check it with an ohm meter and see if it is in range. My thinking is that there might be an internal short in the windings of the IACV motor triggering the "low voltage" code.

There also might be a voltage spec listed at the IACV connector. If there is, use a voltmeter to see if that is in range. That will let you know if the proper voltage/signal is getting to the IACV.

If you don't have access to a service manual, you can make the measurements on your buddy's car for comparison. Or swap parts if he is willing to see if the trouble follows the part.