RPM surge at startup

amccdadbec · Post by **amccdadbec** » Fri Sep 27, 2002 10:17 am

I have a '93 Legacy, 4 cylinder, non-turbo. When I start it in the
morning the RPMs soar to over 2500 then back down to where it almost
stalls. This lasts for about 20 seconds then it runs fine. I've
replaced plugs and PVC. My 92 Legacy starts up and idles just fine.
I'm confused. Please help. Thanks.
Andy

Josh Colombo · Post by **Josh Colombo** » Tue Oct 01, 2002 2:55 am

What octane gas you running? Have you tried doing any diagnostic stuff?
I've got info on my page www.surrealmirage.com/subaru

Josh

amccdadbec · Post by **amccdadbec** » Tue Oct 01, 2002 7:32 am

I'm running 87 octane. I have a Haynes manual and am going to check
ISC. Thanks for reply.
Andy

scott b · Post by **scott b** » Tue Oct 01, 2002 1:02 pm

thats your cold start regulator. i bet it doesnt
happen on warm days or when the engine is warm

amccdadbec · Post by **amccdadbec** » Tue Oct 01, 2002 2:12 pm

You're right. It does not happen when the engine is warm. Is this
an electrical part that I can replace? Thanks for info.
Andy

ciper_ · Post by **ciper_** » Tue Oct 01, 2002 2:12 pm

Id guess you just need to clean the IAC. It has a stepper controlled
valve and a temperature spring. The reason it doesn’t happen when its
warm is the the temp spring has now went far to one side, the only
control is by the stepper.

When the stepper gets stuck it pulls hard then pops open. The Ecu senses
the high idle and closes the valve. This repeats.

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