Posted by David Sherman on Wednesday, November 16, 2005 at 0:53AM :
In Reply to: Pick your brain posted by Dave in Cincy on Tuesday, November 15, 2005 at 7:33PM :
It was running fine. I stopped at a rest area. When I went to start it, it would only run with full choke and very high RPMs. The only possible explanation was a massive vacuum leak. A large plug had unscrewed itself out of the intake manifold and fallen on the ground right there where I parked. I still can't figure how it came loose or why it fell out in the parking lot rather than along the freeway somewhere, but that's what happened. Screwed it back in and everything was fine.
It's a long shot, but are you sure some there's no vacuum leak? If you have any hoses for anything hooked up to the manifold (brake booster, wipers, distr. advance, 70's-style MPG gage, whatever) disconnect and plug the opening right at the manifold. If that doesn't smooth it out, get your propane plumbing torch, take the burner off the end (but leave the valve assembly), put a couple feet of vacuum or fuel hose over the end of it, turn on the propane and point the end of the nozzle around all the fittings, gaskets, flanges, etc associated with the intake manifold. If the engine revs up or smooths out when you blow propane in a certain spot, there's your leak.