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Hi, I have a '04 WRX that had a high idle problem for a little while today, and the fact that it went away has me stumped, and making it a pain in the ass to diagnose. I'm pretty experienced with working on cars, but this stumps me... the fact that it went away on it's own. I guess that rules out anything physical like a vacuum leak, so I'm thinking maybe the computer was causing it? Today was the first time it's ever happened, but I want to figure this out because it's bothering me, I keep my car in perfect condition.

I was on the parkway today, car running perfectly fine as usual. Then I got caught in a traffic jam (something I experience multiple times a day here, so nothing out of the ordinary for my car). It was an accident that just happened, so it was dead stop and go for about a half hour. After about 10 minutes in the jam, my car started to idle high. It wouldn't drop below 1500rpm. If I revved the engine, it would drop back down to normal for a second, but come back up again. The gas pedal was being VERY sensitive to revving it too. I pulled over and checked for any disconnected vacuum lines, but all was good. I also made sure my floor mat wasn't catching on the accelerator pedal and keeping it from coming back all the way... that's happened to me with other cars in the past.

This was particularly annoying because as everyone here knows, these Subies don't like to shift into first unless your input and output shafts are matched close enough. Well of course, since it was idling at 1500, it was being a ***** to shift from neutral into first, something I had to do about 300 times during the traffic jam. I had to keep muscling it in. I was getting really pissed off, since I was beating the hell out of my syncros and there was nothing I could do about it.

Once I got moving again, it was annoying to upshift, because the RPM pretty much stayed steady every time I clutched in. But then after about 2 minutes of driving, it went back to normal. I haven't been about to recreate the problem.

Wild guess: could this possibly be from overheating? I did notice that it felt hotter than normal under the hood when I opened it. Would the computer raise the RPM slightly in order to circulate more coolant if it's overheating? I was driving on the highway for about 20 minutes, then came to a stop and go situation. Shortly after, it started happening. That would be the ideal time to start overheating. Then after moving for a little while the problem went away, which would make sense, there being more air coming through the radiator.

The thing is, my temp gauge was reading perfectly normal, and the fan was clicking on and off like normal, not staying on like I would expect if it was overheating. And it wasn't overly hot out. It was in the evening, around 55-60F. The only thing that makes me think overheating is how it felt when I opened the hood... other than that there are no signs that point to it.

Unless I'm in the far fetched situation that my radiator fan isn't moving as much air as it should, I ended up in the perfect condition to overheat, and my temp sensor is defective, all at the same time, I think it's not the likely cause. But that's the best guess I could come up with.

Has anyone else had this happen to them and can offer any suggestions?

BTW: the car is completely stock, except for an Injen air intake (I know, I know, but it was already in the car when I bought it :rolleyes: ) I know air intakes have caused trouble with these cars in the past, but I think this is one of the few that works well with the car, since it's always run perfectly fine with it. It's the same one that's sold on fastwrx.com, who assures that it doesn't mess with the air/fuel readings.
 

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Sadly I have the same thing happening. I have a stock 04 WRX. The symptoms are literally the same. The only thing that I would like to add to this is that when it is cooler outside (70 and below) there is no problem. But get above that mark and it sucks. I have been reading this forum and others for about a year and tried to find answers to this problem. Keep in mind I have zero experience with working on cars.

I went and got my airfilter changed, my MAF cleaned and checked and my IACV, and PCV checked and or replaced. I did these things from suggestions I heard either here or NASIOC, which I am totally grateful for. Now I have had no luck fixing the problem with all of these tries. I do barely remember a poster on either here or NASIOC say that the cruise control cable gets overheated and makes the engine rev high? I think that is what it said and I can't find the thread after searching briefly.

I do have an appointment with (MACH V/fastwrx.com) on Monday the 21st and will update asap. When I talked to them at MACH V they said that it was a bit unusual that a stock car would do that. Well any help before then would be appreciated.

Java, like I said I have no car experience but so far I have been told the stock intake/ air filter etc... are fine an functioning properly, and since our symptoms are the EXACT same I would say its not your intake. If that means anything. I know it gets pretty hot up in NY and it gets that way in NOVA too, so maybe the common issue is heat?
 

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I'm having this issue as well. Have been for about 8 months or maybe more. I've had it as high as 3000 RPM.

The car is currently in at the dealer now for the 2nd time to try and find it, but they had no luck yesterday but I asked them to give it a good 30 minute drive today and try again. It should be warmer to day, though I've had it happen in cool weather as well, so who knows if that'll help or not.

One thing I have noticed is that I can pop the hood and "jiggle" one of the throttle lines, I have two on a stock '04 WRX, and have the idle lower until, of course, I try to do anything else. This line runs directly from the, I think I'm right here, the throttle body to a black box that is labeled 'cruise assist'.

But, all I've been able to successfully do is get it to drop until I use the car again. It simply drives me :screwy: when it does it. Not only is the car a pain to drive it also really messes with my gas mileage.

So, I guess that's just the long way of saying "me too".
 

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Discussion Starter #4 (Edited)
Thanks for the the replies, I'm definitely going to check out the cruise control cables next time it happens. It hasn't gotten too hot out since the last time it happened, so I haven't had the problem again since then. I bought the car in the winter, so it's only happened once so far, but we'll see, I'm sure it'll happen again. Judging by what you both said I'm gonna take a look at that cruise control cable. The only other things that would cause a high idle would be a vacuum leak, bad IAC, bad EGR valve (all of which basically could be considered vacuum leaks). These would not be intermittent problems though.

Once again, I'm grateful for that cruise cable tip... I would never in a million years thought to check that. If it turns out to be the problem, it'll probably just take some insulation wrapped around it to fix the problem. Or there may even be a way to adjust the cable, there could just be a little too much tension on it, so a temperature change of the cable could affect the throttle a little.

Edit: I went out and took a quick look at it. The cruise control cable seems very taut while the throttle cable has a good amount of slack. This is with a cold engine too. On other cars I've had, both cables always had some slack. There's a foam insulation around the cable, but it might not be effective when it gets too hot. If the problem happens again, there's an adjustment (two locknuts where the cable sits in the linkage). I'll try that.
 

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Well, got the car back from the dealer and got the regular "we couldn't reproduce the problem" - so what's gonna happen is I'm gonna detour their direction on my way home when it is hot out and see if I can be in the area when it happens. That's the best I can hope for.
 

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I had this issue on my 04 STi. Once I reset the ECU, the issue went away. Pretty sure it's the ECU and Subaru's sometimes strange ways of engine management.
 

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:wiggles: OK folks I found the thread that I spoke of concerning the cruise control cable. It was over on the NASIOC boards. Here is the actual quote and I will attach the entire link aswell.

"It is the Cruise control cable. It came from the factory too tight on many of the 03-04s. When looking at the throttle body from the front, it is the cable that loops to the left and attached to a small black box on the wheel well next to the turbo.

This is the issue. As the turbo heats up the area the box/cable deforms and tightens. Loosen the cable to have at least 1/2 of slack while cold and the issue will go away. Do NOT loosen the cable on the right as that is the actual throttle cable."


and the link: http://forums.nasioc.com/forums/showthread.php?t=975833&highlight=reset+ecu

Also my car is at MACH V/ fastwrx.com right now so I will, as I said, let you all know.
 

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Well the Mach V guys checked it out yesterday and they checked all the airflow components and ecu etc....and they found nothing mechanically wrong with the car. So I am assuming they wouldn't know about the cruise control cable so when it happens again I'll losen that and let ya know. Good luck gents
lope
 

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Discussion Starter #11 (Edited)
Yep, cruise control cable it is. We had another really hot day yesterday, and it happened again. Same situation. I was driving for a while, then parked and sat in the car with it on... perfect condition for it to get super heated under the hood.

I revved the engine and came to rest at about 1,200rpm. I popped the hood and checked the throttle linkage, and sure enough, I was able to push it closed and the idle came back down to normal. As I suspected, the cruise control cable was what was holding it open.

It's a really easy fix. The cable housing is attached to the throttle linkage with 2 nuts (cruise is on the left). Loosen the nut farthest from you, then turn the one closest to you counterclockwise until you get a little free play on the cable. Then tighten down the locknut and you're good to go. Solved the problem for me.

I'm not sure what effect this has on the cruise control operation, since I didn't use it yet since I made the adjustment. I assume it might mismatch the speed a little slower the first time I engage it, but it should probably recalibrate itself after that.
 

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I am going to have to try this. The same thing happens to my 03.
 

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same as

yeah, my 04 wagon does the EXACT same thing. Started last year while I was sittin' in traffic on a HOT day. Replaced MAF, lubed throttle cable and cc cable, and it did not away. Took the car to Springfield Subaru and ofcourse...could not reproduce symptoms. Then fall came ....colder temps. and NO more problem...right.....WRONG! Last week ....... again. I knew it couldn't be MAF cause I had just cleaned it 2 weeks ago along w/ new air filter. So the fix is in FINALLY and I will be taking care of the cc cable today. Glad to fix this cause my Cobb Accesport is in the mail!!!!

Thanks rockaloop!:thumbup:

Jon W.
 

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My 06' sometimes does a wierd high idle. When i first start it in the morning it starts, and idles at the normal 1500 or so. then as soon as i put it in first, put the clutch in and let the clutch out and move a bit, it idles up to 2000 for a little while. As soon as i start driving it goes back to normal. It's probly nothing wrong, but i def. noticed it.
 

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Glad to see it worked Java. Mine just did it again yesterday but I wasn't at a point where I could stop and check the cable. Well I am gonna have it happen again today I am sure so I'll be fixin the cable tonight or tomorrow.

How did it work out for you scoutstoo?
 

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Discussion Starter #16
Many more hot days and no problem, so all is good now.

You can check your cables right away, and see right off the bat if the cruise control has too much tension. The cruise control cable should have roughly the same amount of slack as the throttle cable.

The cable should be able to deflect a tiny bit without moving the throttle plate when you press down on it with your finger. Mine didn't. At rest with the car cold, the cruise control cable was completely taut. The slightest pressure would cause the throttle to open a little. If it does that, you most likely will have the problem under the right conditions. Which would most likely be driving on a hot day, then coming to a stop and having the car idling for a while. The lack of air flowing through the engine compartment will allow the whole compartment to get very hot (perfectly normal condition) and in this case, the cable housing to expand just a slight bit, causing the throttle to be held open.

On a side note, I've thought further into this, and realized that it can't be the actual cable itself expanding, because that wouldn't make sense. If the cable expanded, that wouldn't put more tension on it, it would do the opposite. And anyway, a steel cable would not be prone to changing length under these temperatures. What's expanding is actually the black plastic tubing that the cable rides in, causing the cable to become more taut.
 

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yup....works

easiest three second fix EVER. I had noticed how tight the cable was but had never attributed it to the odd high ambient temp rev up. Fixed.

Jon W.
 

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Hey, guys, I was having this problem in my brand new 07 rex, and found it to be two things. One is the hard idle when you first start it up. This is due to the 02 sensor adjusting itself to either burn rich or lean.

The other one is an external intake and/or silencer removal. This causes the mass airflow (MAF) sensor to read differently at idle, causing the car to idle higher. If you have an intake that circumvents the stock MAF sensor, get rid of it and either put the stock box back on or get the Cobb or SPT intake. The solution for this is to disconnect the battery which will reset the ECU.

If you have an AP, i'm not sure if you're gonna have to reload maps. After resetting my ECU, my car didn't idle weird again. And to whoever took it to the dealer and they couldn't reproduce it: they obviously weren't looking very hard, or thought it normal that it idles that high :p My wrx always idles at 500 RPM now unless it's just been started after a night.
 

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anyone have a pic of this?

i don't want to go messing with the wrong wire on someones else's car even though im 99% sure i know the wire
 

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anyone have a pic of this?
Nope, but, when you open the bonnet (hood) and look in the bay the alternator is smack in the centre. Just to the left of this are the two cables, the left cable curls round and back to the cruise control unit in the rear left of the engine bay, the unit says "cruise assy" on it so it's fairly easy to spot :D Both cables have threadnuts mounted in a bracket welded to the manifold running across the centre of the bay, you want the left one, offset slightly and back to the main throttle cable.

I've got an 03 WRX wagon and this problem has been through three dealerships and I've searched numerous forums looking for a fix. They've reset the ECU twice and co-incidence of weather made the problem go away. Moving from San Francisco to Austin made things worse and I was on the verge of selling the car until I found this fix, I made the change at the weekend (hardest part was finding a 12mm spanner), took about 30 seconds and presto, it works, thanks to all for posting this fix. :thumbup: It means I don't feel the need to sell it and buy an M3 instead, not this week anyway :rotfl:

Bruce
 
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