Just came back to my car after being away for a month. Started up fine and drove about 20 miles to do some business. Got back in and while driving noticed the CEL was on. Scanned it and it said P0507 - Idle Air Control System RPM Higher Than Expected

 

First time I've seen this code. The engine is old and has high mileage and was recently installed about a month ago. I will check the hoses for a vacuum leak. The car is driving normal- no stumbling or misfiring.

 

Does anyone have first hand experience with this?

Sometimes the idle air control valve will stick if the car has been sitting. You can remove the hose to it, spray some carb cleaner in there and work the valve back and forth with either your fingers or a screwdriver. (it's a rotary valve)

 

Failing that, you'll need a new one, or you have an unmetered air leak somewhere.

 

Nathan

I think a bad TPS can also cause this code. It's like a potentiometer and can get "scratchy." You can check it with an ohmmeter. But my first guess is the idle air valve.

Where exactly is the idle air control valve?

[...]Scanned it and it said P0507 - Idle Air Control System RPM Higher Than Expected

 

First time I've seen this code. The engine is old and has high mileage and was recently installed about a month ago.[...]

Check the throttle and cruise control cables, etc., and make sure nothing is sticking or misadjusted. It's not uncommon when an engine is replaced for those cables to be too tight and hold the throttle open a bit.

Where exactly is the idle air control valve?

 

There is a black tube (probably 1" or 3/4") from the main rubber/plastic air intake boot leading to the idle air valve. It is next to and kind of below the throttle body if memory serves. It has an electrical connector going to it (three wires?) and two tiny (1/4") coolant hoses going to it. Or you could google/search and probably find a picture....

 

Nathan

Check the throttle and cruise control cables, etc., and make sure nothing is sticking or misadjusted. It's not uncommon when an engine is replaced for those cables to be too tight and hold the throttle open a bit.

 

Are they adjustable? Righty tighty, lefty loosey?

If you own a M/T, this can also be the sign of a defective neutral switch.

 

Car coasting while in gear, very normal, but the neutral switch indicates to the ECU you are in neutral not a gear, so the ECU tries to control the idle speed and is unable to.

 

Later models set a P1507 IIRC.

 

If you have an automatic, follow the recommendations in the service manual for P0507. The above does not apply.

Are they adjustable? Righty tighty, lefty loosey?

Yes, the tension of the accelerator and cruise control cables is adjustable.

 

1) Loosen lock nuts at bracket -- see the attachment

2) Back nuts off so that there's a bit of slack in the cables

3) Readjust as needed -- just remove slack, don't cause cams to rotate --the accelerator cable (1) will seem "tighter" than the cruise (2), because the cruise has a lighter spring on it

4) Retighten nuts, making sure to not change the adjustment(s) in the process

 

This may not be what's causing the code, but it's easy to check.

Alright off to try it. I'll loosen the cables and make a bit of slack. I'll clear the code and take her for a drive on the highway.

Alright off to try it. I'll loosen the cables and make a bit of slack. I'll clear the code and take her for a drive on the highway.

There shouldn't be any slack when you're done with the adjustment. The idea is to back off until there's slack, then adjust until that slack is just removed, and retighten the nuts.

There shouldn't be any slack when you're done with the adjustment. The idea is to back off until there's slack, then adjust until that slack is just removed, and retighten the nuts.

 

Got it.

If you own a M/T, this can also be the sign of a defective neutral switch.

 

Car coasting while in gear, very normal, but the neutral switch indicates to the ECU you are in neutral not a gear, so the ECU tries to control the idle speed and is unable to.

 

Later models set a P1507 IIRC.

 

If you have an automatic, follow the recommendations in the service manual for P0507. The above does not apply.

 

This, 99.9% of the time.

I have an AT.

 

I went out and loosened and then tightened the throttle cable. Also made sure the cruse cable was nice and tight. There is some give to them but they are tight.

 

Now I am getting another code- P1507. When in Park the idle is going nuts- up and down over and over. Also, accelerating is not consistent at all. Sometimes seems like very low power and others it kicks in full.

 

I am thinking it's the TPS. Any ideas? Maybe the Idle Air Control Solenoid Valve?

 

I sprayed down the air hosing with carb cleaner to try to find a vacuum leak. Couldn't find out.

Edited October 14, 201015 yr by bstone

I went out and loosened and then tightened the throttle cable. Also made sure the cruse cable was nice and tight. There is some give to them but they are tight.

Once more, just to be sure we're understanding each other. The cables should be adjusted only just tightly enough to remove any slack, but not so much that the cams get rotated.

 

 

I have an AT.

 

Now I am getting another code- P1507. When in Park the idle is going nuts- up and down over and over. Also, accelerating is not consistent at all. Sometimes seems like very low power and others it kicks in full.[...]

As has already been mentioned, see the attached (click on the thumbnail).

Once more, just to be sure we're understanding each other. The cables should be adjusted only just tightly enough to remove any slack, but not so much that the cams get rotated.

Yes, only the slack is removed. The cams are not being rotated, only the slack has been removed.

 

 

 

 

As has already been mentioned, see the attached (click on the thumbnail).

This Inhibitor Switch is interesting. Where is it located and is it easily replaced? I just so happen to have another EJ25 engine that is complete and I can take parts off of. I am going to take off the IAC solenoid/valve off it and put it on mine and guess I should swap the Inhibitor Switch as well.

The inhibitor switch is on the transmission.

 

Make sure you use a new gasket if you swap the IACV.

The inhibitor switch is on the transmission.

 

Make sure you use a new gasket if you swap the IACV.

 

Where on the trans? Is it by the VSS?

Where on the trans? Is it by the VSS?

It seems like you don't have a service manual. Maybe this will help:

http://www.freepdfdownload.net/1997-subaru-legacy-service-manual.html

Went to the junkyard this morning and got the entire intake manifold (including all sensors and fuel injectors) for $75 off another EJ25. Wow.

 

I replaced the IAC Solenoid & Valve and the TPS, but i am still getting a TPS code, even tho i replaced the TPS. the idle when i turn on the car is at 4.5 RPM. way too high. any suggestions?

Also getting a new code, in addition to the TPS code:

P1700 - Throttle Position Sensor Circuit Malfunction (A/T)

Went and swapped the TPS with the old one and then back to the new one.

 

No longer getting the P1700, but back to the old TPS code. The idle is going from 1.5k to 2.25k over and over. I sprayed carb cleaner down the entire engine to try to find a vacuum leak, but could not.

 

I am at a loss right now. Can I possibly have gotten a bad TPS? What are the odds? Or, am I looking in the wrong place? Should I be looking at soemthing else, like EGR? I have another EGR valve off the junk car.

Update:

 

Cleared the code and put in new TPS. Drove around and CEL came back saying P1507 (IAC Valve). The IACV & Solenoid in there has been replaced, so I am thinking it might be this Inhibitor Switch. Once or twice the AT Oil Temp light flashed 16 times, but it doesn't any longer.

 

So, where do I get the Inhibitor Switch from?

The TPS has an adjustment that has to be made in order for the ECU to know that the throttle plate is closed. The service manual has the procedure for doing that.

IAC valve solenoid is also adjustable, but I think you need a scan tool to check duty cycle to adjust that one.

 

Get an inhibitor switch from a junkyard is the cheapest way. Rockauto lists one under "electrical/switch and relay" - "nuetral safety switch".

Edited October 18, 201015 yr by Fairtax4me

Once or twice the AT Oil Temp light flashed 16 times, but it doesn't any longer.

 

 

the flashing AT Temp light means there was a fault on the last drive cycle. if , when you get it, you turn the car off and on with out driving it it may not flash on the next start up.

 

 

and there are several engine codes which will cause this type of trans code, TPS, MAF, IAC? i'm not sure what else.