General Ford Ranger Discussion General discussion of the Ford Ranger that does not fit in any other sub-forum.

Bogs down when I turn the wheel and idles 800 rpm lower in gear. Maybe vacuum leak

Old 02-20-2019
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Join Date: Feb 2019
Location: Inverness fl
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Bogs down when I turn the wheel and idles 800 rpm lower in gear. Maybe vacuum leak

84 ford ranger with a rebuilt engine. Sat for about 10 years. Towed it home thinking it would make a fun project. Engine was seized, resolved it with a combination of pb blast and some mystery oil. Old carb was leaking from the butterfly bushings so I ordered a new one. Now Iím having some seriously frustrating issues. When I put it in gear or turn the wheel it drops about 800 rpm. The wheel is gradual, depending on how fast I turn it or let it go but the in gear is a steady drop, I can run the truck if I raise the park idle to 2k and loosened the mixture screws to about three and a half turns out. Now the first thought I had was a vacuum leak thatís only noticeable under a load. I started off with some break clean, sprayed it around the engine with it running. Found a few bad lines and replaced them. Still had the rpm issue, so I moved on to the break assist, found a leak there so I unplugged, and capped it from the main vac. Still had the issue so I moved on to the egr valve. It was letting some air pass when I blew through it so I made a block off plate & gasket. Still an issue. Getting a little frustrated I capped all the vacuum lines from the main vac and the carb aside from the pcv valve. Still a leak so I tried changing to a mechanical issue rather than focusing on a vacuum leak. I replaced all plugs and plug wires. Adjusted the timing by ear, and gave about a 10 degree variance to be sure, but no noticeable change other than the rough idle.
Now Iím thinking maybe itís a timing advance issue or my pcv fitting. Shook that and it rattled, but for the cost it probably wouldnít be a bad thing to replace. Now, the distributer has a mechanical advance, I plan on pulling the cap to check the play and if the rotor springs back, but Iíve noticed a few of the wires have been chewed. Aside from that Iím just grasping at straws. Have any of you had similar issues or maybe heard anything? Iím open to any suggestions
sorry for the long paragraph

Last edited by Indelicat0; 02-20-2019 at 05:27 AM.
Old 02-20-2019
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Join Date: Jan 2014
Location: Vancouver, BC
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Welcome to the forum

Test the Vacuum on the engine
$20 vacuum gauge is still one of the best tools in engine diagnostics, even with all the electronics that have been added lately, lol.

18-21" is expected , if lower, the old engine could have compression issue, 1984 engine should run about 150psi

Some tests to run seen here: Technical Articles: Engine testing with a Vacuum Gauge - at Greg's Engine & Machine

Mechanical spark advance is in the distributor, but that's only for RPM advance, you also need Load advance, which was done using engine vacuum(vacuum advance) or from an electronic module that monitors engine vacuum(MAP) or Throttle position(TPS)

Power all starts with compression, which can be partially tested with vacuum gauge
If you disable spark you can test "Cranking Vacuum", good compression engine will be close to 5", but at least 3" is expected as a minimum

Above applies to any size vehicle engine

1984 Ranger had 3 engine options, 4cyl 2.0l or 2.3l, V6 2.8l
2.0l and 2.3l Lima engine does use a timing belt which can stretch or break

Last edited by RonD; 02-20-2019 at 11:00 AM.
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