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Is this a vacuum problem?

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1972 240Z.

After the car warms--and is idling--the RPM will continually fall then rise, but get progressively lower. I have been told that this is caused by a vacuum leak. Would you guys agree?

If so, is there any tried and true method of tracking down a vacuum leak?




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You might want to try this. Use some carb cleaner and spray it near all of your hoses, fittings, and other various areas of concern.

Do this while the engine is running.

When you hit an area with a leak, you will notice that the engine will idle faster.

I learned this trick from a neighbor while helping him work on the same problem.

Sometimes the culprit can be a loose hose. Personally, I like to put hose clamps on the ends of my vacuum tubing. This helps eliminate any kind of slippage.


Mike Gholson

1971 240z, Mikuni Carbs, Tokico 5-way Adjustable Struts, Ferarri Yellow, Stock Engine, 15x9 wheels w/50 series Falken tires, Currently being restored.

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Hi Jon: If you spray carb cleaner around the engine compartment, I'd be careful that you don't spray it on painted surfaces (overspray) or you may loose paint! It does sound possible that the prob a vac leak, but as a recent memory recall hit me, I recall simular problems being caused by worn throttle shafts on the carbs. Sets up an air leak (unmetered, obviously) that messes up your fuel mixture in a random sort of way. Thus the carbs are always trying to "catch-up" to proper mixture. It can get pretty weird.

Good luck on finding the prob whatever it turns out to be!


Carl Stahlnecker

72 240Z "Bambikiller"

HLS30-55703 11/71



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