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In Gear Idle Question



Hello Everyone,

I finally go my new vette to run on its own last night :)
but I still have one problem...

After a small tuneup (plugs,oil,airfilter,pcv,fuel filter) it was idling too low and stalling out, so I replaced the automatic choke, and turned the idle screw (on the throttle cable) about 1/2 turn. Now in Park and Neutral, it idles right around 1600 (what the engine sticker says it should). -with out stalling.

But once I put it into Drive or Rev, it stalls right out. (The sticker says it should idle around 700) If I hold the brake with my left foot, and give it just a little gas, it stays running, and I can drive it around. But once I get to a stop sign/light I have to put it in Neutral, or hold the brake while giving it some gas.

Is there an adjustment for the idle while it is in gear?
Any clues or suggestions would be great.

I have done all of the easy troubleshooting my guides have told me to, but still no luck.

I have also cleaned the carb out good, and all of the vacuum lines seem okay.

Oh yeah, it's a complete stock 1978 L82. With auto tranny.
also, it's kind of sluggish when first starting off, but once the RPM's hit about 2000, you really feel the engine pep up/kick in.
I'm not sure if this has anything to do with it.

Thank you,
Have you hooked up a vacum guage yet?
If not I highly recommend it. A stock engine should have about 16HG at idle. If not adjust your idle screws until you get maximum vacum. If you idle speed goes up more than 100 rpm reduce your idle and recalibrate again. The guage will also indicate other valve/ring problems as well.

You might want to run a compression and or leakdown test as well.

Also try disconnecting and plugging all your vacum lines (except vacum advance) and see if that improves the situation. If it does add them back one by one to find the offender.

Another way to check for vacum links is on a cold engine start it up and spray starter fluid around the base of the carb and intake manifold. If the idle speed goes up you have a leak.

I assume your timing is OK. Be sure to check it with the vacum advance CONNECTED as well as disconnected. With it connected and the timing light on increase the rpm off idle in 500 rpm increments and note the timing at each point. Make sure you are getting enough advance in the 1000 to 2000 rpm range.

Finally disconnect your EGR from the carb and see what happens. If you engine is a high miler the blowby maybe making the mixture too rich. An air fuel indicator is also a great tool but requires you install an oxygen sensor.

Good luck

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