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Old 04-24-2002, 07:02 AM   #1
Jeff P
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Default vacuum leaks, high idle

Ok fellas, got another one for you. My '92 SC's going nuts on idle. It's going up around 3500 rpm when not in gear, and when it is in gear it constantly accelerates. Pretty tough on my brakes and clutch.

So I did the paper clip trick and got code 49, high idle indicates vacuum leak. My question is, how do I go about finding that sucker? I replaced the PCV valve and hoses about 3 weeks ago and everything was working great until Monday. I just gave it a quick check yesterday and didn't see any obvious leaks. Is this something I could find and solve pretty easily myself, or should I just take it into Saturn and tell them this info? Thanks,

jeff

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Old 04-24-2002, 07:43 AM   #2
haplo06
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Hello Great to be here .
I ran into the same problem with my 98SL1 rpm's sticking at @ 2000 I changed the IAC valve and all went bank to normal... cost me 89$and 1 hour of my time (much easier when you remove the T.B.)
HOPE IT HELP'S
PS. My many thanks to all who have posted info here. My baby now run's better than the day I got her.

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Old 04-24-2002, 06:37 PM   #3
sattech
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A bad IAC could set a code 49. The pcm gets no feedback about the IAC position. It tells the IAC to move and assumes it did.
To check if the IAC is in the full closed position and no vacuum leak , remove the snorkle to the throttle body. In front of the throttle plate is a large orifice. That's the port for the IAC. When the car is idling high, plug that hole with your finger. If the RPM drops to normal or actually below normal, then the IAC circuit is not operating correctly.
If the IAC circuit is the problem, then there are two possibilities. A bad IAC or a PCM or wiring issue. To check the wiring to the IAC put the paper clip used to check codes back in. With key on and engine OFF. disconnect the wiring to the IAC. using a test light check all four wires to the IAC. The PCM should be pulsing each wire- with the test light attached to a ground source and probing one of the four wires, you should see the light pulse, then off, pulse then off.....
Each wire may pulse at a different rate, just as long as the wire pulses power it's OK.
If all four wires pulse the problem should be the IAC.

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Old 04-25-2002, 03:18 PM   #4
adventchristian
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SC, single cam? Try the little three holed vacuum plate on the back of the throttle body. I believe there was a factory bulliten on these, you replace them with a new part (from aluminium to plastic, I think)

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Old 04-25-2002, 03:24 PM   #5
Jeff P
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Actually in '92 the Saturn coupe was just called the SC, and came with the DOHC engine, alloys, sport suspension, etc. Equivalent to the SC2's of later years.

I did some poking around last night and couldn't find anything out of the ordinary. I don't think I've got the skills, or more importantly the time, to tackle this one. Maybe next time, but for now Saturn of Frederick will be checking it out for me.

Thanks for the suggestions,

jeff

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