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Clean your Idle Air Control valve (IACV) (Results)

New cars may not have one though I don’t know the exact years. This is more for cars that have a lot of miles on them.

If you read any of my other topics you may know I had idling issues including vibration and sometimes the engine would stumble and shutoff if stopping quickly. I thought I found the solution with a vacuum hose cracked at the base and another one not seated on fully, though that seemed to work at first the issue did not go away totally.
That was after I rented a compression tester and did multiple tests

Then I came across information about cleaning the IACV. Some people have been advised to replace these things which the part alone can cost hundreds of dollars.

Most of the information I found people said to remove it and then clean it. Well I did come across one thing that said there’s instructions in the Factory Service Manual of my Subaru of how to clean it.

  1. Start and warm-up the engine until radiator fan operates.
  2. Hold throttle valve so that engine speed is at 2,000 rpm.
  3. Disconnect by-pass hose from idle air control solenoid valve.
  4. Slowly pour one can (16 oz) of cleaner into by-pass air hole. Cleaner: Part No. 1050002 GM Top Engine Cleaner Part No. X66-A AC Delco Carburetor Tune-up Conditioner
  5. Leave the engine running for five minutes. NOTE: White smoke comes out of the muffler until the cleaner is used up.
  6. Stop the engine.

Those two products listed are essentially discontinued. The AC Delco one is more prevalent online though seems to be only online.

Some people recommended Seafoam though I opted for the slightly less expensive B-12 Chemtool product.

The issue is that when the vacuum hose is disconnected from IACV, the engine wants to stumble and shutoff, so you have to maintain that 2,000 RPM’s. With the product I used, I could only pour a very small amount in each time otherwise the engine would stumble and want to shutoff, all the while holding the RPM’s up.

This is a quote from an individual on another forum in the year 2009, doing the same thing on a Subaru:

… “Started pouring seafoam treatment in and immediately the engine started to bog down and stall. I had to pour it in VERY slowly, while my friend worked the throttle like a madman trying to keep it from stalling when the RPMs plunged, but then letting off when it surged back down.” …

I was kind of concerned whether I used an acceptable product as it did not produce any white smoke. As I continued to read the label it said fuel injector cleaner. I put in about 75% of the 16 ounces then put the rest in the fuel tank.

At that point I was just hoping it wouldn’t mess anything up. I also disconnected the battery for 20 minutes to reset the ECU which resets the saved information on idle.

Driving it afterward wow, it has pickup. It gets moving quick and the vibration at idle seems to be less and does not seem to stumble when stopping quickly.

I think the fact that it was poured into the IACV without removing it and with the engine running allowed the cleaner to get into more parts of the engine and not just clean the IACV. Whereas if I had removed it to clean it then no cleaner would have entered beyond the IACV.

I would recommend at least removing it and cleaning it or using Seafoam Spray in it while the engine is running if you cannot or don’t want to find your vehicles manufacturer instructions for cleaning it. I say Seafoam Spray because that product is used to spray into the air intake with a special adapter while the engine is running and it does not cause the engine to shutdown, whereas other carburetor cleaning products can cause it to shutdown while introducing it in a running engine like the one I tried.