Engine stall

[pahokeehtf]

1979 cj7 258ci 2150 motorcraft carb starts, idles, vacuum gauge reads steady 22hg then drops to 0hg at stall. Restarts then belches white smoke thru carb. Jeep stalls at speed restarts popping clutch. Engine ran good, replaced rusted dirty fuel tank, now have clean fuel, filter and return line in proper alignment, see thru filer clean and full at start and stall. Don't understand power valve in motorcraft carb. New set of plugs didn't help, need help. Valve problems? Help?

 

[k-2]

some things to look at Always easy simple first.
Not consuming fluids, coolant, trans ?
Air fliter on or off is same?
how did old plugs look - wet, dry, black tan?
The Vac dropping hints at an exhaust restriction - gradual vac drop at steady throttle @1500.
The choke plate is full open
Try opening gas cap when stalling - any difference?

Your power valve question

 

[k-2]

OOPS forgot to add this above

 

[pahokeehtf]

Thanks k-2 for your input, fluids all ok, air filter on runs, starts ok, air filter off runs rough, old plugs were worn, dry and ton in color. Choke plate wide open when stall occurs and gas tank is vented so no tank vacuum or pressure. Will remove carb and use rebuild kit from NAPA. Power valve may be the problem or just grunge in carb. Thanks again

 

[bjscj7]

Following - I am having similar problem with my 1982 cj7 258. As with any issue I have with my jeep, the first step I take is logging into jeepz.com and right away I saw this thread. I'm going to take some of the same steps and hope to solve. Question - Could a partially blocked or clogged cat converter be part of the problem? I ask because mine may be. Anyway, pahokeehft please post on how your rebuild works out. I'll update too

 

[k-2]

testing for clogged cat-

1) a exhaust back pressure gauge, you just install in place of a o2 sensor for testing, often a loaner tool but not expensive.



2) Using a vacuum gauge - raise and hold RPM to @1500 observe reading the vac should hold steady f it starts o drop suspect backpressure issue.

 

[pahokeehtf]

K-2, bjscj7, just finished with motorcraft 2100 car rebuild kit, do believe the power valve was the issue as well as grunge. Runs good, idles good, good acceleration, starts good, so it was well worth the effort. No smog, no cat converter, have manual choke on carb, again thanks for the help. NAPA Kit# 2-5585