[dwntwn]

I've had this Suburban for a couple of months and slowly fixing things on it. (1988, 454tbi, th400 trans, 3/4 ton)

It's always seemed to have a high idle, leading me to assume its got a vacuum leak. I replaced the intake gaskets (both on the spacer and the intake manifold), no change. I pinched the hose to the booster thinking it could be the booster diaphragm, no change.

Checked the vacuum hoses, some were old, replaced them all, no change.

Sprayed starting fluid all around the gaskets, intake, throttle body, didn't see an increase in rpms. Not 100% ruling it out, just wasn't able to identify a vacuum leak.

Pulled off the EGR to see if it was clogged (didn't look bad, wasn't stuck, seemed to hold vacuum) no change.

I'm not getting any codes, just seem to have a high idle. I don't have a factory service manual (yet) so i can't check the specs, figured i'd post and see if anyone had any similar experience.

Oh and i confirmed the timing is set at 4 degrees, timing bypassed. (Some people think it should be "0" ) but my core support label says 4 degrees, thats what its set at.

I put a tach in it and here's where the idle is:

• Cold start/fast idle: 1700rpm, moves up to 2100 rpm then after about a minute drops to 1200 rpm and stays there (vehicle in park, AC off)

• Fully warmed up and in gear: 850rpm

Sounds kinda high, right?