Okay, I have a 1997 subrau impreza outback sport and my speedometer stopped working. Along with that I got the code p1507. I was told to clear it because it usually doesnt come back. Well, mine did. I was told to change the idle air control valve so i did put it all back together cleared the codes and it ran perfect. Until the code came back. It runs fine until the code pops up. as long as the check engine light is off it runs perfect but as soon as it comes on once i get it up to about 4500 rpms it starts sputtering and wont go any higher. Any ideas? 

Fix the speed sensor, usually it just needs to be changed.  

 

Also check out this thread.  http://www.ultimatesubaru.org/forum/topic/96627-p1507-trouble-code/

Okay so i got the speed sensor changed. Recently my car has been idling rough in gear and fluctuating in park or neutral. The codes are the same as up top. I took it to the garage that put my newer engine in that only has 36k miles on it. The idle in park sits about 1600 rpms and in gear idling sits around 8-900. It runs fine when you are on the gas. I put a cold air intake on it before i had the engine changed and was put on the newer one. Well recently it started fluctuating and idling rough in gear. I cleaned off the throttle body and that seemed to help a tiny but but not completely. So we took it to the garage today and they told us its because the tube that connects to the IAC should have a check valve in it. but ever single 97 i see does not have that on there along with every Subaru i see. The IAC has recently been cleaned along with the throttle body plate. all new hoses on the intake. Any ideas will be really helpful i would hate to get rid of this car because i have spent so much money and time into it.

Sorry forgot to add there is absolutely no vacuum leaks and i put on a new MAF.

plugs, wires

plugs are brand new E3s. and wires are good.

I'd go back to Stock and see what happens.  

 

Aftermarket stuff can cause strange problems.

I have the original air intake back on and didn't change a thing because the garage i took it to said the same thing. They honestly seem completely stumped about the whole thing. The timing is good. We tried to adjust the IAC valve and that helped a tiny bit. i changed the harness for the IAC. 

The IACV is not meant to be adjusted without having a scanner or o-scope connected. The adjustment is only to set the range of opening that the ECU can control, it will not increase or decrease idle speed. The ECU will change the opening of the IACV to raise or lower idle speed when it needs to, and will learn the optimum IACV opening. The result is, you make an adjustment idle speed changes for a little while, then the ECU tries to set it back to where it should be at 750 rpm. When it can't set that idle speed it sets a code for the IACV because it assumes the problem is with the IACV not reacting to the commands to raise/lower idle.

 

Did you get the speedometer issue corrected?

Are there any other codes besides the p1507?

When you replaced the IACV did you replace the whole valve or just the electric driver on top?

We replaced the entire IAC valve. i still have to get the codes pulled again since i fixed the speedometer problem it was the clip that held the cable in the transmission it was broke. it runs a little bit better with that being fixed that solved a few problems but it still idles in gear rough. 

I did heater core in my 98 outback sport and missed speedo cable whould not rev over 4000rpms untill i hooked speedo back up probly needs speedo cable or speed senser anyway this is normal defalut mode fix speedo

i fixed the speedometer.

Mine I ran at rev limiter for days got better and better It has 320000kms on it and was never reved till I got it now no mercey 5000+ rpms everywere trying to see how hard i can push a stock high km motor see if I can break it. Anyway try retorquing the intake bolts somtimes come loose and suck air

Alright so I got everything figured out with the issues before. Now I got my fuel pump replaced because it got shorted and blew a fuse. That was two weeks ago. And the the fuse blew again. Any ideas? Im hoping it was just a faulty fuse but would it have been able to last 2 weeks?

Also, does anyone know where I could find aftermarket parts mainly im looking for an intake manifold.