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VetteMed · 04-03-2012

If you were able to change coils yourself, then you already can do everything necessary to rule out vacuum leaks under the plenum. A mityvac or similar tool can be used to pull a vacuum on the various lines and fittings under the plenum, unless of course there's something obviously disconnected when you get in there.

If the cruise and/or HVAC aren't working 100% properly, then that would increase the likelihood of a vacuum leak being present.

I recently found a vacuum leak where the brake booster hose meets the plenum. It seemed snug, but after I put a hose clamp on it to snug it up, the idle smoothed out considerably.

Also, a failing throttle position sensor could do funny things at part throttle (not usually at idle, though).

04-03-2012	#6
VetteMed Join Date: Mar 2009 Location: Orlando, FL Posts: 1,816	Re: Not Running! If you were able to change coils yourself, then you already can do everything necessary to rule out vacuum leaks under the plenum. A mityvac or similar tool can be used to pull a vacuum on the various lines and fittings under the plenum, unless of course there's something obviously disconnected when you get in there. If the cruise and/or HVAC aren't working 100% properly, then that would increase the likelihood of a vacuum leak being present. I recently found a vacuum leak where the brake booster hose meets the plenum. It seemed snug, but after I put a hose clamp on it to snug it up, the idle smoothed out considerably. Also, a failing throttle position sensor could do funny things at part throttle (not usually at idle, though).