P1507 idle control system malfunction

Asked by Guru9DLPMH Nov 05, 2020 at 11:11 PM about the 1997 Subaru Legacy L Wagon AWD

Question type: Maintenance & Repair

Occasionally, when I slow down from a high
speed after driving for a while, my check
engine light comes on and the car starts
driving roughly and losing power. If I pull
over and wait 5 or 10 minutes, the car starts
easily and will drive with normal
acceleration, although the engine will not
sound as "smooth" as usual and the check
engine light will stay on for a while --
sometimes only a few hours, sometimes
longer. Once the check engine light goes off
the car runs normally. This has happened a
few times each of the past few years. I had
the neutral safety switch replaced the first
time it happened. Another time I had it
towed to the garage but they were unable to
replicate the problem and their diagnostic
check didn't find anything (the computer
read re: the check engine light was p1507).
The last time was worse because I couldn't
pull over on a hill and I had the gas pedal
floored and was only going about 25 mph.
There was a slight burning smell when I
finally parked. The next time I drove the car
(5 days later) it was fine, and the check
engine light hasn't come on since, but I need
to figure out what is going on. Any advice
would be greatly appreciated.

4 Answers

3,240

Have you checked the idle air control valve? As the rpm increases the pcm will tell it how far to open to adjust to the rpm

1 people found this helpful.
48,060

Although a bit messy, I'd start by removing the plasticware and thoroughly stray-cleaning the throttle bore, inc the upper and lower near-contact points with the butterfly held open. Restarting may be temporarily messy as it purges the cleaner, but that's ok. It could be that your ACV is intermittent (opening when hot, for example). Be careful to not mess up the ACV calibration, as the ECM will flag a CEL if you try to boost idle speed too much, for example. RSVP after cleaning. Ern

3 people found this helpful.

I think this was checked previously when it first acted up but I will have my mechanic look at it. Thanks.

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