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There's a problem though, the wiring on my new 02 sensor has 2 white wires, a black wire and a gray wire. The old 02 sensor has 2 black wires, a blue wire and a white wire. I havn't been able to find any wiring diagrams that indicate voltage on the 02 sensor wiring that would help me figure out which wire would go where...I'm kind of at a loss here. I'm wondering if they jacked the wiring on the 02 sensor and it's sending rump roast backwards readings to the ECU that's causing it to remain in open loop?

 

 

the 2 white wires will go to were the 2 black wires are (heater circuit)  The other 2.......try them one way and if it throws a code immediately switch them to the other way.

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Status update! Since the last post I
did take it into a mechanic. He has a subaru master tech
certification. In the past week that it's been in the shop there's
been a number of diagnostics ran. We both have our hands up in the
air saying what the codswallop, as such he's going to consult other techs
he knows to see if we can divulge. I decided I can also help by
consulting on forums.



 


The engine is running rich.
Codes
presenting are still misfire codes and rear O2 sensor.


In terms of driveability I've taken the
car back for the weekend, cleared ECU to try to get additional codes.
Driving the car it runs fine unless it's trying to idle. When the
engine is warmed up it stalls out at idle. To keep it from dying have
to rev the engine at stop lights.



 



Here's what's been additionally
done and diagnosed at this point.
-Timing. All timing has been
looked at except for removing passenger side timing cover and
determining if it's skipped ahead a little bit.


-Fuel pressure reads at 38 idle w/
pressure regulator disconnected


-Replaced front 02 sensor


-Replaced Fuel Pressure regulator


-Replaced Cam and Crank sensors


-Replaced Knock sensor


-Map Sensor replaced


-ECM replaced with ECM stock unit for
another Impreza


-Injector Resistance 15 Ohm Hot, 14 Ohm
Cold


-Engine pressure 170-180 PSI


-Neutral safety switch reads out
successfully



 


The two standing theories (all long
shots at this point)


-Carbon buildup on engine heads. Fuel
injector is spraying but it isn't reaching the engine due to carbon
buildup.


-The timing belt is a tooth ahead.



 


I'm begging anyone with any additional
theories to suggest them.

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you mentioned a couple of times that you replaced the plugs & wires, but failed to mention what you replaced them with.

 

these need to be NGK - both plugs AND wires, or NGK plugs and OEM wires - Nothing else! Anything else and you are just asking for problems.

 

Checking the timing would be a very good idea. In fact, I would do this BEFORE doing anything else, and do it ASAP. Make 100% sure it is exactly where it needs to be. Being an interference motor, you want to check this sooner rather than later, or you could find yourself with a major overhaul on your hands.

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you mentioned a couple of times that you replaced the plugs & wires, but failed to mention what you replaced them with.

 

these need to be NGK - both plugs AND wires, or NGK plugs and OEM wires - Nothing else! Anything else and you are just asking for problems.

 

Checking the timing would be a very good idea. In fact, I would do this BEFORE doing anything else, and do it ASAP. Make 100% sure it is exactly where it needs to be. Being an interference motor, you want to check this sooner rather than later, or you could find yourself with a major overhaul on your hands.

 

 

Plugs and wires are both NGK. The NGK double iridiums I threw in were sooted up by the time they were yanked again to check them 2 weeks later due to how rich the engine is running in idle. Otherwise it drives fine. This weekend I drove it and it stalled out at stoplights throwing misfire codes. 

 

Timing cover was pulled and timing is correct. Last ditch theory is the fuel injector is shot and that's going to be swapped next. Otherwise we can't think of anything else. 

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At this point I would be looking at scanner data for throttle position, engine load calculation, fuel trims, etc.

Did you ever get the TPS adjusted properly? Scanner data would show that. It should be at 0% with the throttle closed.

 

The rear O2 sensor may not be causing the whole problem but it isn't helping. Gloyales advice on that above is exactly right.

It sounds like a universal sensor was installed, check on the side of the transmission just above the rear crossmember for the harness plug. Hopefully that plug wasn't cut out. If it was you can splice straight to the factory harness, but IIRC the wire colors in the harness are different.

Worst case, the harness that runs along the trans to the rear sensor is replaceable. It should have another plug up near the top passenger side of the bellhousing.

 

After that, and you've verified TPS position is correct, my next steps would be to remove the intake manifold and check it for carbon/sludge, check the intake ports and valves for buildup, and probably replace fuel injectors or have them rebuilt by a professional rebuilder service.

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Plugs and wires are both NGK. The NGK double iridiums I threw in were sooted up by the time they were yanked again to check them 2 weeks later due to how rich the engine is running in idle. Otherwise it drives fine. This weekend I drove it and it stalled out at stoplights throwing misfire codes. 

 

Timing cover was pulled and timing is correct. Last ditch theory is the fuel injector is shot and that's going to be swapped next. Otherwise we can't think of anything else. 

 

Get the stupid double iridiums outta there and put a standard single iridium or better yet standard copper electrode in there.

 

Gimmick plugs suck for these engines.  The tiny iridium tip can't produce a large enough spark and get's worse as it burns back into the ceramic tip.  JUNK.

 

I don't see anything on here about the TPS.  Gotta check it and it's adjustment.

 

Main things tied to idle :

 

IAC and associated hoses

MAF or MAP

TPS.....Must be properly adjusted

VSS

Neutral switch  (it's not a safety switch, doesn't have anything to do with starter.  It's only job is to tell ECU when needed to idle rather than fuel cut for engine braking in conjunction with VSS.)

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I did adjust the TPS correctly. Intake was pulled, there isn't any build up or sludge affecting injectors.

 

Plugs are a consideration, didn't realize double iridium could cause those issues with idle.

 

IAC and associated hoses have been checked.

MAP sensor was swapped with functioning one to verify, no difference.

Grounds have been checked.

Neutral switch was checked and verified to be signalling correctly.

 

Fuel trims are indicating the engine running rich at idle otherwise it's running normally. The problem is idle trims and maintaining idle. It's sooting up plugs and chugging fuel at that point. After engine warms up Tachyometer drops to near 0 when it surges then it eventually regains 700 rpm or dies.

 

What I'm gathering from this is the injectors are a very real possibility. Spark plugs are something to be addressed, and that rear O2 sensor is not a negligible factor. Correct?

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Do one thing at a time here...

 

start with the plugs first - just basic NGK plugs at the proper gap spec is all that are needed here.

(i completely agree with Gloyale - get the stupid double iridium plugs out of there - they are just a gimmick to part you from more of your money)

 

then address the rear O2 sensor.

 

If there are still issues after both of those - then look into the injectors.

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There's really only two reasons for fouling plugs at idle. It's spraying too much fuel, or it can't breath.

 

Actually I suppose a third reason could be that the plugs heat range is too cold, but this usually isn't a problem once the engine is warm.

 

The ECU uses a number called Engine load calculation to determine fuel input at a predetermined rate. This is based on ECT, MAF values, RPM, and throttle position.

The few times I've seen Subarus run so rich they foul plugs at idle and hunt up and down for idle speed, the MAF sensor was always bad and was telling the ECU that air flow was higher than it actually was. High engine load calculation was a sign of that, due to the falsely higher airflow rate.

You don't have a MAF sensor, but you will have a calculated/estimated MAF value in the scanner data from the ECU. It calculates this based on throttle position and MAP sensor values.

If you have an incorrect MAP value, either because of a leak or a plugged orifice or vacuum port for the sensor, that can cause the ECU to add or remove fuel trying to compensate.

 

Are your fuel trims high or low at idle? Basically, high positive trims show the ECU is adding fuel. Negative trims show it is trying to deliver less fuel, but can't or can't adjust the mixture any farther.

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