i've got a 2002 outback, 31k miles. while stopped at a traffic light today the engine started revving up. I switched off the ignition, started the car again and the same thing happened. The third time I punched the accelerator and the revs went back to normal. Sounds like something is sticking but what? I don't know tons about the car but this is something that must be fixed. Any help would be appreciated. Thanks!

Sounds like something is physically causing the throttle mechanism to stick or bind. Do a thorough visual on the complete throttle linkage train. Don't drive the vehicle until you straighten the problem out.

 

Start at the accelerator pedal and make sure that it's not binding or getting caught on the floor mat. Check the full length of throttle cable to make sure it's not kinked or pinched anywhere. Check the throttle-shaft pull mechanism, the cruise-control cable, and the master return spring for free operation. Lastly check for dirt, deposits, or grunge in the throttle-body.

 

If you live in a rural area, it's not uncommon for birds or mice to build a nest on your engine block.

Thanks for the reply. I forgot to mention that after pushing the car to the side of the road a friend was watching both the cruise control linkage and throttle linkage and neither moved at all while the engine was revving like mad.

I'd take Subau of America up on their kind offer of 3yr/36,000 warranty. Let them figure it out or at the very least, create a record on file. Good luck.

a little differnet problem here but some of the info might help you

 

 

Go to Autozone (or another autoparts store) and have them connect their ODBII diagnostic device (usually no charge for this). They can download the CEL code stored in the ECU (the code should still be there even though the CEL is now off). Depending on what the code is, it may or may not point you in the right direction. Sometimes the ECU has to guess what the problem is and it guesses wrong, but its usually not hard to figure out where the true problem lies.

 

Temp sensors are really common on Subaru's. There are two sensors, one for the dash and one for the ECU, it is the ECU one that fails. Its about $40 for a new sensor. If the temp sensor is gone, the ECU will think the engine is cold and run it in cold mode (high idle).

 

I would rule out problems with the throttle cable first though, problems in this area are not too common, but they are really easy to rule out and correct.

 

I haven't seen any broken return springs on the throttle body, but I have seen binding accelerator and cruise control cables. I would check that the cable ends are clean, and with another person moving the accelerator pedal check the throttle/cable mechnism out for any signs of binding. You can lubricate the return springs, but generally the cable ends and cables are not lubricated because the lubricant can draw in dust and dirt. Also check the cable case for kinks and damage, sometimes the cables are damaged during repairs (pinched or dropped tool). The accelerator cable may be worn out and in need of a replacement, not too common, but it happens.

 

You can clean the throttle body and its springs with carb cleaner, sometimes this will free up the throttle mechanism.

 

Also check out this thread on Idle Air Control (IAC) valves, malfunctioning IAC valves will cause really erratic idle, and in some cases cause the engine to idle at 3,000 or so RPM (if the IAC is stuck open).

 

http://usmb.ultimatesubaru.org/forum/showthread.php?s=&threadid=7944

 

Another possibility is a failed Throttle Position Sensor (TPS) but this is not very common and the ECU is very good at identifying it, just check that the throttle position sensor is still firmly attached to the throttle body, if it is loose the ECU may get the wrong throttle reading. If loose you will have to tighten it back up in the original position, hopefully you can find the "dirt line" that denotes its original position.

hope this helps some- maybe the IAC?

http://forums.nasioc.com/forums/showthread.php?s=&threadid=541467

 

Similar problem on WRX.

when you say "revving like mad" do you mean it is running high or the engine is really revving itself?

Take it to the dealer . SOA just issued a recall on 127k suby's . they say that the throttle cable is getting stuck . Has something to do with the cruise control cable also . They are rubbing together and SOA is putting on sometype of after market brace .

 

Mike k

i would check the idle air control valve, if its acting up tap on it with a screwdriver handle or something similar. it might free it up for the time being, but still replace the i.a.c.v. ifits faulty. they dont always set codes if they are intermittenly not working.

Today, on my way to work, I noticed that even when my foot was off the gas that the car would continue to accelerate. However it was slow, and I saw that my cruise control wasn’t on, so I brushed it off. As I got closer to work, I came to a stoplight and noticed this unintentional acceleration getting worse. When I was driving into my parking space, the car abruptly , ON ITS OWN ,mind you, revved up to 6000 rpm . As fast as I could, I turned the car off. Later in the day, my cousin came to help me look into the problem. Two things we found, number one, there was a chip of wood stuck between the butterfly valve of the air intake on the engine manifold. ( where the Engine metal meets the plastic) 

We assumed that was the issue, as wood chip was actually allowing air to get into the system and rev the engine even without pressing on the gas pedal. The real question was how a piece of wood big enough got into that area. That’s where the second problem comes in , I noticed while putting the air filter back in place that before this whole situation I had never had the filter latched in correctly. There’s 2 notches on the bottom of the plastic cavity and you need to make sure the air filter is clicked into those before snapping on the clips at the top.  
 

I hope this information helps anyone with a similar problem. I believe the wood chip got in because that air filter was not correctly connected. 

crazy!

I have had to replace the lower section of the air box on both my cars, the 'slots' that hold the top's tabs had broken-out.

sometimes when the top doesn;t get seated, it will make a noise.

David M, thanks! I think I have the same problem.

I just started up my 2003 Legacy L SE wagon for the first time since December today (had left it on the opposite coast). I did a 3.5 mile test drive around the hilly, rural block. At two points in the drive, the car floored itself. When I pushed in the clutch, the engine would go up into the red at 6500+ rpm, so I let the clutch back in and used the brakes to slow me down to prevent overrevving. It was then normal for a few minutes, before it floored itself the last mile to the end of my loop. There is evidence of animals living under the hood, nut shells and stuff - it had been completely clean under the hood when I had left it in December.

I'll clean all the debris out when I get a chance tomorrow, especially the air box and throttle body where you found stuck wood chips. I think I might find more debris left by animals.

Edited October 19, 20205 yr by Lightning Racer

Here was the damage . The inside of the throttle body was corroded, with the throttle plate turning green too.

Edited October 21, 20205 yr by Lightning Racer

spoob man I’m glad I posted about my issue! Good luck getting all that crap out of there. At least air filters are cheap. Will the car run or no ?