legacycentral bbs

Ok this may be a little long winded and all over the page...

I have had the minor rough idle problem for quite a while. When I installed my vac/boost gauge a while back it read low in vac and boost and vrg3 was helping me with troubleshooting ideas. I did the starting fluid check for a vacuum leak and came up empty. We came to the conclusion that the gauge is most likely miscalibrated as it was only reading -15 inHg and hitting fuel cut at 9 psi. Anyways take this into account later.

My car has been running very strong since I got my Saab 900 i/c piped in but sometimes when I stop at a light the engine would stumble slightly like the car wanted to stall then smooth out quickly. This would not always happen. Yesterday I was driving on some back roads and the car was running real strong with no real problems until I drove through some pretty deep crusty slush for about 1/2 a mile. After that the car seemed strange when just cruising along (kinda jerky) but even stronger under boost. I was in second at one point at WOT and someone pulled out so I let off the throttle and the car jerked hard then smoothed out deaccelarating normally. I never noticed it doing this before so I went WOT a couple more times and let of the accelarater and it would do the same thing, jerk real hard when the throttle plate closed then smooth out. I pull up in front of my house the car almost stalls. It would stumble real bad then the rpms would shoot up to 1k then stumble and almost stall, shoot back to 1k over and over real quick. I turned the car off and restarted it and it wasn't as bad but still was real rough and not steady. During this time my vacuum readings went to about -10 inHg on my gauge(most likely about 14 inHg), uh-oh. So I popped the hood to see if I could find a vacuum leak and couldn't find anything obvious however there was a strange clicking sound coming from somewhere around the air filter box. I turned off the engine and took apart the airbox because I thought maybe snow was blocking the intake and choking the engine or something. No luck, bone dry, no snow. I put the intake back together and try to restart the car and it would start then stall. Now I really start to panick but my dumb ass forgot to hook the MAF back up. I hook the MAF back up and the car starts but still isn't running good. I go ahead and pull the codes off my ECU and got 24 IAC valve (which is one I had before and cleared but it came back) and 49 MAF code which was because I forgot to hook it back up. Now with the code 24 I never got a CEL. I go ahead and clear the ecu using the green connector method and get the all clear. I reread the codes using the black connectors and the codes didn't clear. Ok so I turn the a/c on to see if the IAC is acting wierd and it almost stalls the car. It's running real rough, turn it off and the engine smooths out turn it back on and it works fine I again try to clear the codes and get the all clear but they're still there in read mode. I go for a drive and the car's real wierd under partial throttle and at idle but runs like a raped ape under WOT. Today I went on some errands and it was more of the same. At one light I would have
-11 to -10 inHg vacuum and the engine would be stumbling then at the next light I would have -15 inHg and normal smooth idle. Again under WOT the car pulls extremely hard. I'm totally confused. I got home and did the starting fluid check again and still couldn't find a leak buit noticed the "clicking" sound but not consistant. Could the clicking be the pressure sensor or exchange solenoid valve? Could this all be a faulty IAC valve? I wouldn't think so but I'm at a loss. Any help would really be great.

I don't know what would be clicking near the air filter... But if you're counting the area all the way up to the strut tower, then it could be the boost control solenoid or pressure exchange solenoid. The pressure exchange solenoid shouldn't repeatedly click no matter what, but the boost control solenoid does.

To me this really does sound like an IAC valve problem. If it's sticking or not turning smoothly, then when the ECU needs to start using it to maintain engine idle (like when you snap the throttle shut or stop at a light) it might fail at first and then catch itself and work. That's just me guessing, though.

I don't know how part throttle stuff would figure into that, though.

Well it sounded like it was near the air box but I figured it couldn't be and the pressure sensor and exchange solenoid seemed more logical so that's why I mentioned it. Would the boost control solenoid click repeatedly at idle though? I've never noticed it before really. I was in a pretty good panick though when I was checking it out. I was having visions of blown gaskets and lots of $$$ ( which I guess is still a possability) .

Would the IAC effect the vacuum readings though?

The partial throttle feels like an ingition or fueling problem. Like bad plugs or wires or maybe injectors. I don't know though because at WOT it runs really strong. That's what's throwing me off.

Are you coming to town this next Monday vrg? If so we should really try to hook up. Maybe we could go for a ride and you could give me your expert opinion

I know it's rape, but you might want to think about a trip to the local Subaru dealership. Try talking to a tech that works on TURBOS, and get an opinion... or let them charge you an hour and you get out the door with 80 less dollars in your wallet, but some peace of mind.

Then again they might tell you nothing you didn't already know and rape you for the heck of it. I'd try talking to someone on the phone, maybe call Langston Subaru and talk to a tech.

The boost control solenoid is always repeatedly clicking when the engine is running. It's just the duty cycle that varies.

Any time you have a bad idle you'll get bad vacuum readings. It can be hard to determine which is the cause and which is the effect.

I may have already asked you this, but how old is your fuel filter?

I will be in Williamsport on Monday. I was wrong about the time before, though; my hearing is at 4:00pm. I may want to use the morning to go visit the location of the incident and stuff to refresh my memory, but afterwards I'd love to hang out. If you PM me directions from 1965 Lycoming Creek Road, I'll be there sometime between 4:30 and 5:00. :)

vrg3 wrote:The boost control solenoid is always repeatedly clicking when the engine is running. It's just the duty cycle that varies.

That's probably the cause and I was just panicking.

Any time you have a bad idle you'll get bad vacuum readings. It can be hard to determine which is the cause and which is the effect.

well that's good to know.

I may have already asked you this, but how old is your fuel filter?

I just replaced it about two months ago.

I will be in Williamsport on Monday. I was wrong about the time before, though; my hearing is at 4:00pm. I may want to use the morning to go visit the location of the incident and stuff to refresh my memory, but afterwards I'd love to hang out. If you PM me directions from 1965 Lycoming Creek Road, I'll be there sometime between 4:30 and 5:00.

Cool, I'll pm you later today =).

Brat4by4 wrote:I know it's rape, but you might want to think about a trip to the local Subaru dealership. Try talking to a tech that works on TURBOS, and get an opinion... or let them charge you an hour and you get out the door with 80 less dollars in your wallet, but some peace of mind.

Ya, I may end up doing this if I can't figure out the problem on my own, which so far I haven't. I'll probably try a new IAC before hand since I keep getting a code on it.

Unless you've got a really really good tech there (and they're extremely rare), I don't see what a dealer or shop could do... Most of them just follow troubleshooting charts in manuals and keep swapping components out until they think the problem's gone.

In this case, it would probably go something like:

Replace the IAC valve because there's an IAC code.
If the problem's still there, look for a vacuum leak. Fix it if it's found.
If it's still there, check fuel pressure. If it's incorrect, replace the regulator and/or pump.
If it's still there, clean the fuel injectors. It's good preventative maintenance anyway.
If it's still there, replace fuel filter, air filter, ignition wires, and/or spark plugs.
If it's still there, painstakingly perform all sensor tests described in the service manual.
And so forth.

That's all just an example... but you could do most of it yourself.

'Course, asking them for advice could still be useful. But unless you think they're gonna do something different from the above, I wouldn't pay them to diagnose this problem.

Thanks to vrg3 we discovered the probable cause...the O2 sensor .

I started a new thread in the exhaust forum to further discuss the issue.
http://bbs.legacycentral.org/viewtopic. ... 9588#39588