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Oct 1, 2002
Midland Texas
Ok my cruiser has just developed a rough idle. Plugs are good, wires are good, good distributer cap, good rotor, good coil. So I pulled out the trusty vacuum gage and this is what I found.
A steady 5 hg of vacuum. My haynes book says it should be 17 hg. It does not jump around just a slow steady 5 hg. I checked the timing about 6 months ago and it was fine. I also have a problem with it backfiring when it's cold and pinging sometimes around 2500rpm. Are these problems related. ??? I need some direction.
You don't say what year you have, but it sure sounds like a vacuum leak to me, regardless. I'd be looking at the brake booster, the front-drive switch, the hoses connecting them to the manifold, and the manifold itself and gaskets. I think you will find the answer to both of your problems somewhere in there.
It's an 87 FJ60 and the vacuum system looks like 2 octopus mating under the hood.
Grab a can of carb cleaner and hoes down the engine. When you get close to the vacuum teak it will draw in the carb cleaner and change the idle. this should give you a good idea as to where to start looking for your leak if that is the problem.

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