legacycentral bbs

subyluvr2212 wrote: Josh, I definitely won't do it since I got reamed on the new one, but is it possible to use a rotary valve on a 90-91 MT?

Not exactly sure.....

How should I go about adjusting the idle then? I really don't know which screw/nut/bolt to turn.

technically....there is no way to adjust the idle manually. It's controlled by the computer. The computer want's it at 700 rpm and will adjust the various sensor/IAC/injectors, etc to get it at that idle speed. The only time it wouldn't be able to fulfill this correctly is if a sensor is malfunctioning/sending a bogus value, or if there is some outside force that has driven the engine speed control and sensors outside their range of operation.

So like I said earlier....there's probably another issue somewhere. Where or what that issue is....I couldn't tell you without troubleshooting it.

I tried taking the iac sensor out to clean it. I got 2 of the 4 bolts out then thought to remove the pcv air tube inorder to get in there better, while i was pulling on the tube for it to come off I must've pulled too low. As the part of the tube attached to the pcv valve came off so did the bottom part, and with it a piece of whatever it was attached to. It looks goes from the air intake thingy to this "T" splitter, one part goes to the tranny and the other part to the pcv valve. Just out of curiosity what is this thing and what does it do? Also I started the car up to see if it got fubar'd from this. It started up then almost died for about 5 seconds but eventually got up to regular rpms. After it warmed up it would start up and the revs would go up to 2k then go back down to about normal.

that t thing the pcv valve is connected to comes from the engine crank case (main tube, and also has a line that goes up to the intake tube.

Well I got a used t-thingy and iac valve(too bad the dumbasses at pick-n-pull didn't know what it was even though I told them it was an idle air control valve yet they still charged me for a smog pump or some stupid crap it wasn't). I compared the two and mine was way too sticky, so hopefully this fixed the idle problem, we'll see in a while though

Guess Ive been away for a while, didnt know it was possible to ruin an IAC by cleaning. I think its odd this would happen, Ive cleaned 5 on legacys personally...

The idle level can be effected by a failure in the charging system. Rotating the IAC servo and Top throttle plate bypass screw will let you center it to get better control of idle, and partially effect cold idle.

For the most part cold idle operation is a purely mechanical setup with the valve trying to compensate for the coolant temperature controlled portion.

Regarding the charging system, one of the legacy I bought didnt idle in specification and I wanted to get it just right for smog (750 +_ 50 if I remember right). I messed with adjustments for quite a while and thats how I found the throttle bypass screw to IAC corolation.

In the same car I always had a high idle, I got it to be stable at around 800rpm. After replacing the alternator and battery (ill tell the story in another thread) the idle has dropped considerably (150rpm based on dash gauges, havnt connected my tach yet).

One thing to make sure is that the Idle contact swith in the TPS is functioning properly.

I believe the new cleaned iac valve fixed it, I haven't had it die at idle since I changed it, so I'm hoping that's what it was.