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steezie19 11-14-2012 11:09 AM

New to this site and need HELP!
Hey guys I'm new to this whole forum thing but I don't know where else to look. I have a 1999 subaru legacy brighton and I have done lots of work to it since I bought it off my boss who has also done lots of work/upgrades. But recently I have been having this really weird idling issue, while im stopped or parked, my car will rev up and down, it has never stalled when it does this and it dosent cause any other problems. I currently work at a garage as well and i have done lots of tests on it like smoke test to look for vacuum leaks and nothing, I have changed my IAC, TPS, and MAF sensors and still nothing. I have looked on many other forums and still have not found what could be causing this issue. I also have a fuel pressure gauge hooked up to the fuel line right before the fuel filter and while it does this idling problem the fuel pressure dosent drop any more then a few psi and maintains 40psi when idling normal. If any one can help that would be greatly appriciated. PLEASE HELP ITS DRIVING ME INSANE!!!!!!

mungewell 11-14-2012 12:00 PM

It might be the ECU cycling the revs to confirm that the Cat is functioning, which might be a problem with the Cat itself or the rear O2 sensor dying.

You could just shut the engine off when parked ;)

pfoyle 11-14-2012 12:01 PM

I am NOT an expert of any sort...

Do you have something you can use to read any engine fault codes? Could be a misfire in one/some of the cylinders (which could be caused by bad spark plugs or bad gas or faulty ignition coil)... there are lots of things it could be... best bet is to check the ECU with an OBD reader and see if it gives you any clues...

steezie19 11-15-2012 12:42 PM

I have scanned it several times no codes no misfires, the cat is brand new and so is the rear o2 sensor again I've looked at every thing I can think of I even did an ecu relearn several times by disconnecting the battery for several minutes and hooking it back up and nothing. This is why I'm so confused and again it never stalls. But recently I've noticed that when I turn the AC on or the rear defrost it runs fine no revving issue so I'm thinking possible alternator or voltage draw somewhere but I dunno if that makes Sence

BigBlack-V 11-15-2012 12:48 PM

does this only happen when its cold? It might be a long shot but the 08 LGT has an issue with the o-ring intake manifold gaskets. When its cold and contracted air gets in and causes the car to stumble. Does it go away when the car is warm or goes it happen all the time?

Grimmrican 11-15-2012 01:02 PM

Did u erase ur codes after installing the parts and doing a drive cycle? If its not ur iac ( which I was gonna say) it prolly ur throttle body. The spring is prolly stuck. Do u have a sticky gas pedal?

MrTris 11-16-2012 09:57 AM

In my experience, that's a voltage (ie - battery, alt) issue. I suggest new or rebuild alt and a grounding kit. Should be pretty straightforward between your experience and having a B-Right On.

PeterJMC 11-24-2012 09:53 PM

You should post and search in the Third Generation forum which are focused discussions on your model/year.

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