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legasti 10-06-2012 10:03 AM

Strange P0519

Got a strange problem going on, didnt know if anyone could shed some more insight with past experiences. Have been looking online, google, searches for the last 2 weeks and either the syptoms are different or other codes played a part in throwing a P0519
Car is a 03 legacy, 2.5 N/A MT.

CEL p0519 Idle Air Control System Performance

Car acts like it is cutting fuel in 2 cyl when your are driving in gear and let off the gas. Idles fine, runs good untill you let off the gas while still in gear. I am able to drive the car with no issues by making sure the clutch is pressed in before the gas is let off. Also by not letting off the throttle while driving(always accelerating).

What I've Checked:
-Checked the wiring from all of the sensors on the throttle body(they are all components of the idle system).
-Bench tested all the sensors which I was able to find specifications for. Replaced with known good senors: IAC, TPS, MAP, Air assist injector solenoid. Drove and still had same issues.
-I have cleaned all of the sensors above along with EGR, purge control valve.
-Intake has been smoke tested with no leaks found.
-Performed a FISC, pulled injectors to check for particles
-Made sure all pathways for the air off of the IAC were clear, all the way to the injector ports.

Any thoughts or ideas is greatly appreciated, even if i listed it i will try it agian. Thanks again

rockhammer 10-09-2012 05:13 PM

Sorry to resurrect but did you ever figure this out? Could it just be your clutch beginning to go?

legasti 10-10-2012 05:14 AM

I have not figured this out yet. The clutch is newer and I and turned away from wear parts like that because it only happens when you let off the gas if it were the clutch I would think it would happen every time you let off the clutch. Thanks though for the thought.

BeKnwn 10-10-2012 05:44 AM

I decided to look some stuff up and give you guys an idea have you guys checked the neutral switch? Seems to be the source and fix of a lot of people

Cause it controls the IVAC, it tells the ecu when you press the clutch and adjust the idle valve, makes sense right? Hope it helps you guys

octain11 10-10-2012 08:21 AM

was about to say, did a repair like this before, youll need to change the neutral switch on the side of the transmission, error correction gets confused and doesnt know if your in gear or not , it thinks the idle air control sensor is not adjusting the idle and sets the code, hope this makes sense

legasti 10-11-2012 05:25 AM

thanks for all of the responses. I just figured it out last night. The neutral switch was something that i did test as well, as well as replace it with a good one off of a scrap car.

The symptoms were happening when the car was bought, which it didn't seem like a big issue, the guy said he had tried a few of the sensors which effect the idle but didn't get any to work. The car also had oil leaks and bad carbon build up due to not changing oil properly, it was more like it drained it or burned it off and the guy just filled it up.
I tore down the engine, did heavy cleaning inside getting it looking new which i also replaced the block because the one had some scratches in the cyl walls and i didn't want issues with it so i had another 2.5 block, and did head gaskets, water pump all seals, everything while the engine was out. the new block had a slightly different pcv system, it had a y splitter off of the crank breather tube one end went into the intake the other went into the air box. Different from the one that just went to the intake manifold. Not realizing what i had done until i had one of those moments, i essentially gave myself a giant vacuum leak whenever you let off the gas, making it sputter and throw the IAC code. So when all other hope is lost, look at the stupidest mistake you could have made during the install and fix it. Thanks for the responses, hope no one else makes this mistake.

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