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Premium Member
2001 Outback VDC Wagon
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76 Posts
Discussion Starter · #1 · (Edited)
Good morning!

Creating yet another P0507/P1507 thread as a comprehensive guide for H6 owners having these issues.

As of posting, I elected to 'shotgun' all of the common failure parts, listed with part numbers below for your reference (took me a ton of time to know what exactly what to search).

Current Symptoms:
  • Issue first appeared after replacing the brake master cylinder (and moving a lot of engine bay components around).
  • Car runs fine overall, but idles high.
    • Upon starting, surges to 2000 briefly, settling to 1100-1400 within 3 seconds (cold) or 900-1100 RPM (warm).
    • EZ30D factory spec (w/ no engine load) is 600RPM +/- 100 (at sea level).
  • Car "bucks" forward repeatedly at low speeds (<30 MPH), accellerating then disengaging repeatedly.
  • Car holds speeds (almost like the throttle is being held down a tad) up to 40 MPH, and accelerates up to 25 MPH slowly if left unattended.
  • After driving, and in Park, tapping the gas causes the car to immediately throw a "CHECK ENGINE" code, with a 90/10 split of P1507/P0507
OEM Parts Purchased:
IACV Gasket22659AA1201$5.28
PCV Valve11810AA0211$16.03
Hose Assembly PCV (Driver Side, Front - Direct to Crankcase)11815AB0621$17.63
Hose Assembly PCV (Driver Side, Rear - Direct to PCV)11815AB0831$35.19
Automatic Transmission Gear Position Sensor31918AA0001$63.73

Why buy?
  • IAC Gasket (22659AA120)
    • Cleaned the ICAV a few weeks back trying to fix this issue, but had to reuse the old gasket (a no-no). Replacing this. 20-year old rubber is no longer rubber (hoses included).
  • PCV Valve (11810AA021)
    • Don't know when this was last replaced. A dirty/malfunctioning PCV valve can cause excess pressure in the crankcase, causing oil leaks, poor idling, etc.
  • Hose Assembly PCV (Driver Side, Front - Direct to Crankcase - 11815AB062)
    • Front hose on driver's side crankcase. Connects front port of the crankcase to the air box (prior to throttle body)
  • Hose Assembly PCV (Driver Side, Rear - Direct to PCV - 11815AB083)
    • Rear hose on driver's side crankcase. Connects the PCV valve somewhere(?) near ICAV.
  • Automatic Transmission Gear Position Sensor (31918AA000)
    • Certainly not required, but wanted to eliminate any electrical gremlins. I had to replace a relay a few weeks prior, proving electronics can fail, especially when they are 20 years old and used in punishing environments.
Day 1 Installation:
Parts Installed:
  • ICAV Gasket (22659AA120)
  • PCV Valve (11810AA021)
  • Hose Assembly PCV (Driver Side, Front - Direct to Crankcase - 11815AB062)
  • Hose Assembly PCV (Driver Side, Rear - Direct to PCV - 11815AB083)
Process and Results:
As expected, all rubber components were damaged in some way. The gasket had been entirely pinched off in one section, and the previously rubber hoses were distorted and brittle, with moderate cracking in some places. After starting, the engine did idle better, and a tad lower at around 800 RPM. However, tapping the gas while in park immediately threw the P1507 code again.


Day 2 Installation:
Parts Installed:
  • Automatic Transmission Gear Position Sensor (31918AA000, FSM "inhibitor switch")
Process and Results:
The installation process took a bit to find in the Factory Service Manual (FSM) refers to this part as the "inhibitor switch". You can save some time and see it attached. Overall pretty simple. Only change was I kept the transmission clip (linking the cable assembly to the transmission case) on during the installation since the upper bolt is tight. You can slip off the connection between the cable and switch gently after you take off the lock pin without any issue, and shimmy the switch out and in to save time.

While the car runs much smoother (and overall tangibly better), the original P1507 code persists. When idling, in park (P) and tapping the gas, the engine will rev, idle higher for a moment, then throw the code without fail. Going to do some more research, but hoping it's not an expensive sensor or whatnot (throttle position sensor, or ICAV itself?).

Will reply to this thread with "round 2" of diagnostics after creating a new attack plan.
 

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Premium Member
2001 Outback VDC Wagon
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76 Posts
Discussion Starter · #2 · (Edited)
Given the above parts didn't solve the root issue, creating this reply to segregate the next "attack plan":
  • Clean all visible engine bay grounds with steel wool and brake cleaner. Reinstall cables with squirt of silicone lubricant (to prevent oxidation & water intrusion).
  • Per this thread (04 Outback H6 3.0 P0519 P0507 high idle and surging)
    • Going to take off and clean the EGR and re-install with new gasket.
    • Going to re-clean throttle body.
  • Use FreeSSM to troubleshoot TPS voltage levels to see if within spec (see attachment).
  • Use FreeSSM to troubleshoot IACV metrics in accordance with the P0507 code. (see attachment)
My hope is that I can avoid purchasing a $150 sensor, but we will have to see.

Will edit this reply with the full results of the diagnosis and next steps.

Diagnostic Process:
Pulling the initial data set from a warm engine. Upon starting, the P0507 code was thrown pretty quickly.


It seems that the IACV duty cycle is low, hovering around 15%. Funny part is, that if the duty cycle is <60%, the diagnostic says "END" with no further direction, i.e. no "replace this, or refer to that". The plot thickens...
 

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Premium Member
2001 Outback VDC Wagon
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76 Posts
Discussion Starter · #3 ·
After completing all of the above items, the issue still persists...

The car will creep forward, and then surge and buck at low speeds. Tapping the gas in park immediately throws the P1507 code.

One tidbit of information: while the car is bucking in drive, the ignition timing will oscillate between 15-25 degrees, in sync with the bucking. Any thoughts? Currently at a loss here.
 

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Outbacks, SVXs, XT6, 4Runner, Celica, Brat, E150s
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Ignition timing changes considerably based on engine load. So that's probably a symptom.

Sounds like a sticking idle valve. I'd be looking for a used one to swap on there.


What engine components did you move to replace the master? Shouldn't have had to do much, unless you were doing the booster as well. Still might be worth capping off the booster line to rule that out as a possible vacuum leak point (warning: you won't have power brakes, use caution).
 
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2001 Outback VDC Wagon
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Discussion Starter · #5 ·
What engine components did you move to replace the master?
Other than shoving some cables and whatnot, nothing was "unbolted" persay. I replaced a majority of the pipes I may have hit (PCV hoses etc.)

I will do the brake booster hose next, since I do need a proper 11/32 suction hose, currently using a 3/8 fuel hose.

Data collected while driving shows what could be a weak/failing alternator? Before I was enlightened by this forum, I had a parts store (aka garbage one) installed.

Voltage dips into the mid 12s at some points. Attached some data collected during a 30 min drive this weekend. It's really a CSV, but I can only upload TXT files so I just changed the extension?

Will continue updating, planning on biting the bullet and getting an OEM Mitsubishi alternator because they shouldn't go bad too often.
 

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Outbacks, SVXs, XT6, 4Runner, Celica, Brat, E150s
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Brake booster hose needs to have a check valve in it. Use the OEM hose.
 

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2001 Outback VDC Wagon
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76 Posts
Discussion Starter · #7 ·
Brake booster hose needs to have a check valve in it. Use the OEM hose.
Gotcha, I was looking around for the JDM version of the booster hose, but couldn't find any definitive part number. I will keep on the hunt, but would you happen to know a thread/starting point I could look at? This does make sense, as I did see a P0507 code shortly after swapping the engine with a JDM one with a generic hose...
 

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Outbacks, SVXs, XT6, 4Runner, Celica, Brat, E150s
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I take it you have a jdm engine? That will be RHD. There's a pipe plug in the intake manifold on the LH side that can be removed and the fitting from the RH side swapped over.
 

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2001 Outback VDC Wagon
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76 Posts
Discussion Starter · #9 ·
@Numbchux - I indeed do have a JDM engine. I will explore relocating the port, thinking this is potentially fuel related due to the logging below?

Here's the logging when the car begins to excessively creep, up to almost 25mph (off screen). During this time, the CPC Valve Duty Ratio steadily increases, suggesting an issue with the emissions system? See the logs below, and more on the CPC here:


495148


While the "bucking" occurs at low speeds, the fuel injector pulse width (which I assume controls the duty cycle, and therefore the amount of fuel) drops from 4ms to 0ms briefly, then back to 4ms. This only happens at idle (throttle closed, at low speeds) while the TPS Voltage is 0.64 (dead on within the spec of 0.3 - 0.8 v, ignition on, no throttle).

495146
 

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Outbacks, SVXs, XT6, 4Runner, Celica, Brat, E150s
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My guess is that it's air related, and the ECU is cutting fuel as a reaction.

Using bulk hose (no check valve) between the engine and booster could potentially cause strange vacuum changes, which could possibly cause running issues. That check valve is there for your power brakes to work correctly, it's much less likely to cause your problem, but it definitely needs to be fixed. Could just cap it off for diagnostics.

I would definitely swap in a used idle solenoid, but I have parts cars. If you've got a UPull yard nearby, maybe watch for an H6 car to come in and grab one.
 

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2001 Outback VDC Wagon
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Discussion Starter · #11 ·
Using bulk hose (no check valve) between the engine and booster could potentially cause strange vacuum changes, which could possibly cause running issues. That check valve is there for your power brakes to work correctly, it's much less likely to cause your problem, but it definitely needs to be fixed. Could just cap it off for diagnostics.
Thank you for all your advice @Numbchux, I ordered an OEM brake booster hose (26140AE100) this evening so we can eliminate that variable, and it should be arriving soon (2-4 days).

As far as re-locating the brake booster port, would we want to swap the red port with the green-boxed plug? Essentially making it USDM hose compatible o screw-on ports?

495163

495165


Will visit a U-Pull-It next week to grab an idle control solenoid (among other interior items to spruce it up a bit)
 

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2001 Outback VDC Wagon
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Discussion Starter · #12 ·
Updating this after awhile. I purchased a 400 PSI 3/8" air hose from a local hardware store since basically every local (and I mean every) auto part store managed to not have 11/32" vacuum hose in stock (really?). The bouncing issue has been resolved! However, the idle is about 100RPM above factory spec (730 vs 600). This could be the computer adjusting, so I will update after driving for 2 hrs tomorrow.
 

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01 Outback LL Bean
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I was unsuccessful attempting to remove the passenger side brake hose plug. It is threaded and glued in I believe.

Get a barbed brass coupler and some fuel pressure hose and extend the brake hose to the drivers side port of the JDM engine.
 
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