Buzz wrote:
> My '96 SL single cam has 185K on the clock, and has been running fine.
> A few weeks ago I changed the oil and hosed off the motor with a
> garden hose. Then the "Service Engine" light came on, but it was
> running fine. A few days later it went off, and my buddy at work
> hooked up his code readed and said it had a EGR related code in the
> memory.
> I drove it a couple of weeks, and light stayed off. It wouldn't start
> the other day, and wiggling the battery terminals got it to start, so
> I drove it home and cleaned the terminals, which really didn't look
> bad at all, but I polished them bright with a wire wheel.
>
> The next time I drove it after the terminal cleaning, the engine had a
> high idle, and would race up to 3000 RPM when I would clutch it
> between gears. the idle would eventully settle down to 750 RPM.
> Drove it to work today, and it still would race up between gears,
> almost like I wasn't letting off the gas pedal when shifting. When I
> would put it in neutral coasting up to a stop, the engine would be at
> 2000 RPM, then slowly drop to a 750 RPM idle. No check engine light
> is coming on at this time.
>
> What could be causing this?

Yeah, I had that happen. When I stopped at a traffic light, the rpms
would be 2k to 3k before dropping down to idle speed after 30 to 40
seconds. The accelerator pedal and cable were fine. The 'service
engine soon' light did not come on. I thought the throttle body might
be gummed and sticking so I removed it but it was actually fairly clean.
I cleaned it up anyway and reinstalled it but the problem didn't
change. But...the throttle body had a little solenoid valve and piston
attached to it that opened and closed a little bypass hole around the
throttle body butterfly valve. Turns out that is the 'idle air control
valve' (IAC) that opens to allow the flow of air through a little hole
about 1/4" in diameter that provides the air to the engine for idling
when the throttle butterfly is closed. I didn't think it could be bad
because there was no fault code or SES light but I decided to change it
as there wasn't much else that could be causing the problem. Et voila!
The problem was solved. I got the new one for $50 at car quest. It
only took about 15 minutes to change on my '92 SL2 (221K on the clock now).

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