98 OB Legacy- update on troubleshooting a difficult P1507

[aaron.cavosie]

Hi folks,

 

Since Sept. I've been stuck with a P1507 code on my 1998 Legacy Outback (2.5). The code is triggered everytime I decelerate going downhill, weather the car is cold or warmed-up. When the P1507 started, I also lost my speedo (but not the tach). I can clear the code with my code reader, but it reappears whenever I next decelerate, leaving my car stranded at home. I can reproduce the P1507 like clockwork. I like DIY work, but I've been stuck on this one for 4 weeks, and miss driving my outback.

 

I've tried a variety of solutions so far, but these have not fixed the problem:

(1) new spark plugs + wires (no change)

(2) new air + fuel filters (no change)

(3) new neutral switch (no change)

(4) I checked for voltage to the IACV, and also proper resistance on the IACV plug pins (all checked out)

(5) I removed and carefully cleaned the IACV (Q-tips, carb cleaner, gas), using a new gasket. (no change). I did throw a P0505 (air control) and a P0325 (knock sensor) the first time I started up after reinstalling the IACV, but they did not return after I cleared them out with the code scanner.

(6) I have tried to check for a vac hose leak by spraying car cleaner on various hoses and listening for the throttle, but haven't detected any effect so far.

 

The next thing I'm going to try is to replace the vehicle speed sensor. I've held off on this one until going through the items above, as the speed sensor seems to run about ~$150. But now it seems to be my only option left, and might make sense given that my speedo also went out when this problem started.

 

Any other thoughts about what might cause my P1507, given the above info?

 

Thanks, Aaron

[twisty]

after removing and cleaning the IACV, did it work correctly? cleaning it and checking voltage doesnt necessarily guarantee the valve/mechanism is opening enough, or quick enough every time for it to not toss a code once in a while.

[aaron.cavosie]

You got me- I guess I don't know how to evaluate if the newly cleaned IACV worked correctly or not. When I first started the car, it idled very rough (sounded terrible), and I thought I screwed something up. Right away the P0505 and P0325 showed up. I used the code scanner to erase the codes, and when I re-started my car, it idled perfect, and the P0505 and P0325 codes did not return. Everything sounded good.

 

But as soon as I drove down my driveway, my car stalled as I came to a stop to turn, and the P1507 showed up again. When I re-start the car, the idle is horrible, and the car barely drives. This is the same pattern as before I cleaned the IACV. When I erase the P1507 the car drives normal again, until I go downhill and decelerate. Then it all happens again (P1507, horrible idle).

 

I get the P1507 systematically, reliably, every time I decelerate to a stop when going down a hill, and then the car idles terribly upon restarting. This persists until the code is removed.

 

Is it the case that the IACV can stop functioning, even after being cleaned? I don't imagine that they are cheap to replace, but I'm getting desperate enough that I might need to shell out for one if it seems like it might fix the problem.

[snederhiser]

Hello;

Things to check,

Air cleaner housing and all intake tubing

TPS

MAF

O2 sensor

Knock sensor

Cam and Crank sensors, Steven.

[snederhiser]

Hello;

I forgot that a bad EGR/Solenoid will cause a rough idle, check this first, Steven.

[Ivant]

Maybe it's time to bite the bullet and check it into the local subie dealership. Sometimes it's the last resort if all else is failing.

[IrishLt]

If you get this figured make sure to let us know. The 1507 is notorious for not having any solid fix.....the Nss replace and a good Iac cleaning is the closest fix there is and it only fixes about half of the instances of people popping this code. Wish I could point you in a direction that you haven't already went.

[aaron.cavosie]

Maybe it's time to bite the bullet and check it into the local subie dealership. Sometimes it's the last resort if all else is failing.

 

Boy, I would gladly be a 'bullet biter' and take it to the dealer to sort out my P1507, but its not that easy for me. I live in a remote mountainous region of Puerto Rico, and the nearest dealer is over an hour away. My driveway is over a km long through the jungle, and consists of very steep hills and valleys, the kind that you need an Outback to drive on. With my problem, I can't even make it down the very first of several hills on my driveway without throwing a P1507 and stalling out.

 

I'm going to keep forging ahead on the DIY route, thanks in no small part to advice and tips offered here. I have considered trying to find a tow rig with serious 4WD capability to pull me out of my hilly home front. It might be possible, but it won't be easy (or cheap...). For now, I'm systematically replacing one part at a time and checking to see if it solves the problem, so hopefully I'll be able to identify the real culprit causing my 1507 woes. I figure all the other stuff I replace/repair in the meantime will give my 98 a longer life span.

 

Thanks all the same.

[Osei]

after removing and cleaning the IACV, did it work correctly? cleaning it and checking voltage doesnt necessarily guarantee the valve/mechanism is opening enough, or quick enough every time for it to not toss a code once in a while.

 

+1 ^

 

Did you remove the electronics from the top when you cleaned it?

If not, do so, since you know how to adjust it to spec again.

 

O.