Smeddy2

So I have done some reading on previous threads and I have tracked down my surging idle problem to be my IAC valve aka auxiliary air valve. I took it out and cleaned it up really good and that fixed the problem for a few days but now it's back. I have a feeling the small coolant lines are getting clogged with rust and build up that was in the coolant. I've drained the coolant and replaced with water a couple times and have even added Prestone flushing additive but it doesn't seem to be working. Is there some product you know of that will clean out all my coolant lines? If anyone has cleaned their IACV , do you coat the valve with some sort of silicone spray to make sure it opens and closes smoothly? I just cleaned it out with brake parts cleaner and slapped it back on the throttle body.

Smeddy2

Bueller?

bigpaw

My IAC valve was not working and the truck had the idle surging problem when warm. I hooked up a clear PVC hose in-line with the coolant line that connects the IAC to the nipple next to the thermostat to check to see if coolant was flowing through...It turned out it wasn't flowing more than a few drops...Found out later that the mechanic my brother (previous owner) took this truck to extract a broken thermostat housing bolt must have dropped it down into the engine and it was just the right size to plug up the passage in the thermostat housing (about a 8 by 8 mm piece) when the coolant flow started. But it would only plug it up sometimes and then fall back down other times. After one long trip the surging was pretty much happening all the time, the bolt piece was stuck pretty well in there. I could see the piece blocking the passage below the nipple when I took off the hose and pulled the thermostat. I put a rag in the block passage so it wouldn't fall down into the block again, unscrewed the nipple, and punched the bolt piece down into the "bowl" where the thermostat goes.

Anyway, the first time I thought I fixed this problem I hooked a MightyVac with the fluid catching attachment (like for bleeding brakes) to the hose to the IAC and began drawing coolant backwards through the IAC to make sure coolant was flowing though the valve. It was. But, I collected lots of rust and white crystals, enough to fill the catching jar 1/4 full. Kept drawing coolant this way until the coolant ran clear with very few rust flakes (could have gone crazy, but figured 99% was clean enough). Thought this would fix the problem, but since it was the bolt piece, it didn't.

However, I will probably "vacuum" the IAC out as maintenance every once in a while now, because this area does not flush well apparently and it is very easy to do. Note that normally the coolant flows the opposite way, from the thermostat through the IAC valve, but somehow the normal flow doesn't wash the crap out. That is why I think that a normal flushing product or water flushing can't clean the IAC. Any flush will flow the same path as coolant. If the valve was pulled and the coolant passages cleaned well with a hose from both directions, i don't think it would still be dirty.

As for lubricating the air passage piston, I wouldn't use silicone spray because of the potential to damage the oxygen sensor, and silicone doesn't play well with mineral oils. I would however probably lubricate it lightly with a very light oil like K&N air filter oil (since it is okay for intakes) or something like that (maybe even a couple drops of seafoam since it has a light clean oil and solvents that could clean it). I like seafoam as a WD40 type cleaner/penetrant/light oil.

Smeddy2

I don't have a mighty vac but maybe I can find something that can pull a vacuum on it. I know when I had it out, I tried blowing air through the coolant passages and it had more resistance than what I felt was okay. I was hoping this flushing additive was going to help clean it out more. I will try the sea foam bit, too. I didn't think mine had any sensors in it. I don't recall pulling off any electrical connections... Mine just looked like a spring controlled valve.

Smeddy2

Well I hooked up a hose to the line to see if I could blow water through the valve and it was so blocked I could only get a drip. I ended up having to take off the throttle body again and clean it out the AAV with an awl. I replaced my radiator with a clean one and flushed the system as best I could. Hopefully this will solve it. So far it is working perfectly. Nice smooth idle at 750 RPMs and I even fixed my clutch fan while I was at it!

bigpaw

Glad to hear you got it fixed. Wish I could get smooth idle without misfiring. I even pulled injectors to replace seals and get them cleaned and that didn't help a bit. They were all nearly the same fuel volume and spray pattern anyhow; one off by maybe 2 or 3 cc.