legacycentral bbs

Ok...Yesterday for the first time, I started my car like normal (already been through half a tank of gas) and instead of the revs holding around
1.5 K or so like normal for the first minute of startup, they immediatly dropped straight to ~400 rpm as the engine sputtered and died. I restarted it, and held the revs at ~1K manually for about a minute, where it settled back down fine to normal idle of 750 rpm. ???
Driving it around is fine. Full boost is normal and everything.
I am re-setting the ECU right now, to see if that would help at all.
Any one else experience this/Have any ideas?

On a side note, I replaced the caps on the stock boost solenoid that came off to fix that small vacuum leak I had. I have gotten quite an increase in milage per tank (about 50 more miles or so per tank).

Sounds like another damn IAC problem. When I screwed mine up, it stuck closed and it performed exactly as you described. I started it up and no matter how cold it was, it went no higher than 500 rpm roughly...

Start the car cold again and see what happens, if it does it again, start searching junkyards for a new IAC valve, since they run about $360 new from the dealer. If it doesn't do it again, keep your fingers crossed and hopefully it stuck only that once...

I doubt any of you will ever need a replacement IAC.

Its probably one of the simplest parts on the vehicle, a shaft with a magnet that seals of an air passage and a metal spring that changes shape depending on temperature.

The top portion is just a couple coils that drive the magnet like a stepper.


Most often a cleaning is all that is needed. I did have to adjust it on one of my cars, after a complete tune up including cleaning all the build up gunk in the intake and PCV system the Idle was too high.

OK, I know it's nearly a 7 year bump on this thread. I finally got around to cleaning my IAC on my '90 n/a, it hasn't worked or about 3 years(my bad) and now it is idling at about 3000 rpm. So after it started doing the high idle I first let it run for about 10 minutes and little change, if anything it revved higher. then I took it back apart to make sure there was no vacuum lines missing or loose, while it was apart I started the engine and it ran at about 2000 rpm, I reached into where the coil spring goes and turned the little thing in there that the coil turns and it revved up when I turned it. Then I put it back together tried it again and once more it ran about 3000 rpm, so I unhooked the battery for about 3 hours and tried it again. This time it ran at about 2200 rpm then started climbing slightly. I then shut it off and thought maybe I put the coil in backwards. So again took it apart and brought the coil into the house and ran it under hot water to see which way it turns as it heats up, seems that I had it in the right way, based on what I observed by turning the thing inside the coil housing with my finger.

So I'm kind of stumped. Does the solenoid have to be sealed on the top of the unit? It didn't seem to be when I removed it, no gasket or goo.

Thanks in advance.

Is this on an MT or AT? I'm guessing the MT since that's what you have in your sig.

The MT valves on the 90-91 MY's are kind of a pain. I've never taken one apart, so hopefully someone else that has can chime in.

Yeah, it's a 5 speed manual. Honestly it looks like such a simple thing to cause so much headache. I thought about adjusting the idle screw down at the bottom of the TB, but thought I should seek some advice first.

Do not touch the idle screw at the bottom of the TB.

Do you have one of these needle valves at the top of the TB? If so, you could adjust this to adjust airflow around the TB. However still sounds like there's an issue with the IAC valve.

http://main.experiencetherave.com/subaru/images/TB/

Needle valve? I don't actually remember seeing anything like that, but that doesn't mean it's not there, I'll check for it later. There is the stop adjuster on the linkage lever. That's the one I already adjusted when the IAC stopped working, idled too low so I turned it up, the summer came and I turned it back down.

As far as the one at the bottom of the TB I never touched it. I remembered having read some where, probably here, NEVER adjust it.

Since it would start, idle low and gradually increase idle speed to normal as it warmed up before I cleaned the IAC, and now it starts at 2000+ rpm I believe that the IAC is causing it too. As I said before I'm just stymied at the moment. Maybe that needle valve holds some promise, but before I do any tweaking I'm goint to pull the IAC again and make sure everything is sealed. Still not sure if the solenoid portion is supposed to be sealed or not. Any one?

Yesterday I got back to it and discovered that I had a huge leak in the IAC gasket, had it off and back on twice and both times the gasket slipped, stupid, LOL. Any how I got the idle down from 3k, but didn't fix the original problem. I couldn't fin any procedure for checking the old style IAC, so I put a meter on the 2 contacts and it has 100% continuity. Did not check this before tearing into it because I never got a CEL. I think it should have any where from 50 ohms to 150 ohms of resistance, if that is correct, it has a direct short.

Can any one confirm if this is correct of not

Sounds like you're on the right track.

Just now I uncrimped the housing and unwound the coiling of the solenoid, slowly. I unwound about a foot at a time and kept checking the ohms with the meter. About 8 or 9 feet in I started getting 10 ohms of resistance, so I started winding it back up, soldered the two ends back together, reinstalled the solenoid back into the housing and put the whole thing back together. I then started the car and it worked perfect...for about ten minutes.

Shut it down , checked the resistance, still at 10 ohms. Checked the voltage at the plug, still 12 vdc. Pulled the solenoid off plugged it into the harness, had the wife turn the key on and it pulls the plunger in.

WTF!!

Does any body reading this have a '90 or '91 that has a working solenoid type IAC? If you do could you please take a resistance reading and report back to me what your ohms are?

Lunatech wrote: Does any body reading this have a '90 or '91 that has a working solenoid type IAC? If you do could you please take a resistance reading and report back to me what your ohms are?

BUMP!

I disagree with people saying never to adjust the throttle body screw.This is only true if no one has done it before on your car lol.Many shops have done it on alot of our cars even though it shouldnt have been touched,if it has been fucked with then you DO need to adjust it.

True, but it states not to touch it in the manual. So if someone did, shame on them. There should be paint on it to show you if it's still lined up from the factory.