Idle problems... again!

[entirelyturbo]

Here we go again, this seems like the problem I was having only a few months after I got the car.

Recall, I replaced my throttle body because I had messed with stopscrews in the past and had no way of returning them to their original position. So I have an untouched throttle body with all factory settings and a good TPS.

I've been noticing my idle dropping to about 500rpm lately, and since all of us have had weird idle from time to time, I pretty much ignored it...

Until today. I was heading toward a turn, so I put the clutch in and slowed down. I had a clear shot, so I began to turn, when I noticed I had no power steering. I looked at my dash and lo and behold, my dash lights are on and my tach is pointing at 0

I took the turn without PS and then turned the engine back over and continued on my way to work.

I really really don't understand why it's doing this. This is exactly the same thing it was doing when I first got it, except the fact that I have an IAC valve that is less than 2 years old, I have absolutely everything fresh in my car, the engine is in a perfect state of tune. I have not had a CEL come on in almost 2 years.

What have I got left to try?

[Legacy777]

well unfortunately I'll say that our tachs are incorrect.....and what looks like 500 rpms is really around 700 rpm if you look at the reading the ECU is getting. Why it stalled, I don't know. Mine's been a little cranky too, however I really don't drive it too much lately, since it's being a whore, and all I do is travel 5 min to work.

You could try an ECU reset or something.

[entirelyturbo]

If I'm correct, the halfway point (thinner line) between 0 and 1 is 750 rpm, and the line right ahead of 0 (thicker line) is 500 rpm.

But nonetheless, you say that the ECU is reading it higher? Do you think that the tach is actually correct and the ECU is reading it wrong, or vice versa?

I was thinking about trying an ECU reset, thinking it could possibly have something to do with the weather being a tad cooler, not much but a little.

[Legacy777]

I'm pretty sure the ECU is correct. I'd have to put an external tach on to verify it though.

[vrg3]

Has it stalled itself out again since then?

Do you have access to a laptop with which you could make my scantool? Since you mention that it's cooler, I wonder if maybe the ECU's seeing incorrect coolant temperatures or anything like that. Seems like a long shot though.

Have you tried cleaning the MAF sensor out?

What kind of air intake and filter do you use?

[entirelyturbo]

Nope, it just did it that one time. In fact, on the way home last night, the tach never went below ~600 rpm.

I'm gonna do an ECU reset as soon as I get off the comp, and let it sit for the rest of the day. It rocks having a second car

My friend has a laptop, but to be honest, I dunno if I wanna go through all that .

I would like to eventually get a Select Monitor like some of you have...

I could try cleaning the MAF out, but I have a feeling it won't do much good.

My intake is completely stock, complete airbox with snorkus still in the fender, and I'm using a Purolator paper air filter.

[vrg3]

It would be cheaper for you to buy an old laptop than it would probably be to get a Select Monitor (if/when you ever have a chance to buy a Select Monitor), and my scan tool can do nearly everything a Select Monitor can on our cars.

Honestly I don't think an ECU reset is going to solve the problem; the car isn't supposed to ever require ECU resets. At the very best it would mask the problem.

I'd say to try cleaning the MAF sensor out... Since you've already got everything that one normally would think of, you may as well try the things that seem less likely.

All your vacuum/PCV hoses are in good shape, right? No chances of any leaks?

Is your PCV valve fresh?

[entirelyturbo]

PCV valve is about a year old. And from an age-old discussion that we had before, Mark (LegacyT) mentioned that his father, a Subaru mechanic, said there is no need to replace a PCV valve unless it has failed.

But who knows, it might be acting up or have already failed, I haven't checked it since I installed it.

I'll check out vacuum hoses and all that today.

Thanks for the help guys

[vrg3]

From what I understand, PCV valves' springs can weaken without breaking, so the valve can start to malfunction and screw up mixtures without actually failing. That's why they say to always replace the $2.48 valve rather than just cleaning it. But maybe that's just propaganda from PCV valve manufacturers.

[tris91ricer]

Really, they're only $2.48? umm.. ok! I'm replacing mine.
topically, I de-snorked my 92 recently and now have idle problems, as it idles too high, and then when it does drop, it goes down to ~1k, sometimes lower, and then the CEL comes on. If it's in any drive gears, none of this happens. However, if I'm in N or P, it idles high, sometimes up to 2k. If I give it gas --rev it to make it drop to 'normal' idle speed, it drops, but will go right back up. Other times, it'll drop, to about 1k, and idle fine.
Is my IAC on the way out? If so, why would de-snorkifying my intake cause this? It didn't do this on my 91, in fact, it only made things better!
Any suggestions, while we're talking about this?

[vrg3]

http://www.partsamerica.com/PartDetails ... ber=PV1019

That's weird that removing the snorkus could affect the idle that much.

When the 4EAT is in gear it provides more load for the engine, which could be what's responsible for keeping the idle stable.

Your ECU isn't thinking it's in a 5MT car for any reason, is it? Do you have access to a laptop to run my scantool?

[entirelyturbo]

Shit!

I broke the little plastic PCV tree that sits on top of the block! One yank on the hose to get it off the PCV valve and half of the tree came with it.

After that I just went to the dealer and ordered a new tree and a PCV valve. Might as well while I'm fiddling with it.

It just sucks that I have to wait until Tuesday, and that I'm driving the XT daily, when I'm trying to keep mileage off of it

[vrg3]

D'oheth!

You mean that weird tee with one 19mm end, one 12mm end, and one 15mm end?

I don't get it. Why is that part made of plastic?!

You might consider ordering that hose, too, since it sounds like yours is pretty hardened. It's part number 99071AA170, but is pretty pricey at 20 bucks...

[BAC5.2]

When my car kept shutting off while driving, it was due to the IAC.

I replaced it, and the wiring, and all is well now.

I suggest you do the same. I have a brand new IAC I'll sell you for cheap.

[vrg3]

He'd need a custom hose at the least to use a turbo IAC valve.

You make a good point about the wiring -- it's quite possible that this problem is an intermittent open or short circuit. But you'd expect to see an occasional CEL.

[mikec]

How often does the ECU's code check that the IAC is working properly though? Maybe its enough of a wiring problem to affect the idle, but not enough for the ECU to notice? I dunno.... It is a very strange problem though.

And with regards to that plastic tee - I hate that thing!!! After I broke mine, I promised myself I will only ever change and/or do anything with the PCV valve and tubing when its warm, so that there's some give.

[vrg3]

I think it checks practically constantly.

Yeah, it's nerve-wracking to touch the PCV hoses, because you never know what you might break. We should make replacements for all those plastic pieces out of some kind of metal. Copper or aluminum maybe.

[mikec]

Ok, well that rules that out then. Hrmm...

As for the piping, didn't ciper suggest something similiar at one point? Basically appropriately sized vacuum hose and fittings.

[THAWA]

As far as the tach being incorrect its not, the lines are right, you're just reading it wrong . You have to count down from 1k instead of up from 0. Quite a few people seem to think that though. I think the reason they did this is under normal conditions the engine wont be in the 0-500 range, so why have a reading for it? Just like the speedo, there's no 5mph on that because the car isn't meant to be driven so slowly, honestly that's the best reasoning I can come up with

[vrg3]

Mike - Maybe he did; I don't remember. We'd just have to make sure to get the shape right to maintain PCV functionality.

THAWA - Yeah, most of the marks on the tach are 250 rpm apart, so the one below the 1000 mark should be 750.

[Legacy777]

vrg3, can you explain to me a little more what you did for BAC5.2's re-wire of the IAC valve. Did you just run wires to tap into the existing lines at the ECU, or what exactly did you do? Was the wiring harness that fubared?

[vrg3]

Well, we suspected that it was just the "close" signal that wasn't making it, but I just wanted to make him something he could plug in that would completely eliminate any questions about the wiring.

So I made a very short extension harness for the 28-pin connector of the ECU. All the pins went straight through except for the two IAC valve pins.

For those pins, I connected long wires on the ECU side (the car side of the harness did nothing). The long wires go all the way into the engine bay, where they terminate in a connector that plugs directly into the IAC valve. Thus, the IAC valve's "open" and "close" pins are connected directly to the ECU, using none of the factory wiring.

The IAC valve also needs a +12v supply. For this, I made a tiny extension harness for the 3-pin connector for the coil pack, splicing into the middle one for +12v. That wire goes to the IAC valve connector as well. This way, the factory power supply wires for the IAC valve are eliminated; as long as the ignition coil gets power, the IAC valve will too.

I made it to verify that his problem was in the wiring harness somewhere. That's all. And it worked.

[entirelyturbo]

Didn't get a chance to respond, been working overtime...

Phil, I just put a whole new IAC valve on the car not 2 years ago. I seriously doubt there's something wrong with it already. And my wiring should be fine, I've yet to have an electrical problem with this car.

Hardy, that's exactly what I said the tach increments were. The mark below 1000 is 750, and the mark below that, right next to 0, is 500. My tach would point straight at 500 sometimes.

And if anyone fabricates a metal replacement for this plastic piece, count me in!

[BAC5.2]

I never had any electrical problems with my car either, then one day I was coasting and the car turned off and the CEL came on.

I have a strong feeling that the IAC I had was bad anyway. My problem got BETTER once I replaced the IAC, and it was solved when I rewired it. I ran it for like 4 or 5 months with the stock wiring on the old IAC, so that is probably what killed it.

[entirelyturbo]

Wow, someone give me a dunce cap and send me in the corner!!

Patti was still misbehaving today, and I was noticing some light-dimming when it was idling. I thought it was my new(ish) alternator going bad, voltage regulator or something, so for some odd reason (I dunno what I was gonna do) I popped the hood...

Out of the corner of my eye, I saw the intake hose almost completely OFF the MAF sensor!!! The strut tower was keeping it somewhat in place. So I put it back on and tightened the clamp down, and I checked the clamp on the throttle body side and it was loose too!

I'm actually glad this is what it was though. This isn't the first time this has happened... Why do these clamps keep coming loose? Should I put some Loctite on them or something?