Chevelle Tech - View Single Post - Finding Vacuum Leaks
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post #9 of (permalink) Old Jul 20th, 19, 4:09 PM
Dave Ray
Senior Tech Team
Join Date: Apr 2012
Location: Yerington, Nevada
Posts: 1,877
Re: Finding Vacuum Leaks

DUTCH gives a good answer, again. Look at the plugs.

Case in point, one year when I still lived in So. Cal., I had to go through the Socialist by-ennial smog torture tests with my first year 2.8 V6. Engine had developed a single cylinder miss. So, I get in there one day, and go testing, plug wires, plugs (found the lean cylinder, number 6, driver side rear). Looked at cracked this or that, loose whatever, couldn't find it, dead plug wire, cap, name it. Then, it hit me, the only thing I didn't check was the EGR valve, mounted just over the number 6 inlet port. I pulled the valve, liquid checked it in my solvent tank, leaks, not giant ones, but 3 fairly bad ones. New replacement EGR valve, smog check, passed with flying colors, to the point the inspector grilled me on what I did to make the ting pass, because NONE of them he has ever tested, passed. I never did get to the point of the EGR valve in the story to him.

Nope, never did think to use my propane method on that leak problem, probably would have showed it up a lot faster if I had.

On the propane, I use a hand held propane torch, UNLIT, UNLIT, UNLIT. I also use that method down the carb if I think there is a lean condition from the carb jetting at a designated throttle opening, very low flow propane down the air inlet with throttle held at a set RPM the leanness seems to be. Engine loads up, too rich, engine speeds up, too lean. Besides, burned propane smells better than gasoline.

Also, when I propane check, I leave the brake booster fitting in the booster, and check the whole power brake system as assembled.
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