the pinch test.
hot engine.
1/2 the air for 800 rpm power, comes from ISC
and 1/2 the bleed. (when duty is at 50%)
there are no other air supplies
armed with those facts.
you can pinch the ISC, if RPM does not, cut in half,(1/2) or stall?, then at the same time ,turn the BLEED CW. (closing this last supply of air)
the RPM MOST FALL to 400 or stall. if not? there IS A LEAK (vacuum)
IF SAY IT DId, then the bleed was turn all the way out, letting in huge amounts of air.
usually when you have say a small air leak (vacuum) and idle is too high
and you start turning the bleed screw CW, at some point the ISC wakes up(its not pinched now) and idle Locks in at 800rpm , regulating.
The bleed screw can hide some small leaks, (with in the range of the bleed, and ISC)
but most leaks get worse in time, and above is just a band-aid to nowhere...
once i get an engine running right ,not misfiring, or bogging, i do this test (pinch) and bleed checks,per above
before doing any duty cycle tests or precision spark timing. (timing needs idle near 800 +freeze jumper)
if there are no major leaks , i then do the duty cycle calibration and for sure, on all new Throttle-bodies.
and we have a cheap meter that works now. off ebay.
i just tested it from 5v to 18v and a wide ranges of ISC frequencies (or is 200hZ) it works great.
keep in mind all 8v engines make full power, with vacuum leaks, the engine might scream and make huge power when the iSC looses control.
hot engine.
1/2 the air for 800 rpm power, comes from ISC
and 1/2 the bleed. (when duty is at 50%)
there are no other air supplies
armed with those facts.
you can pinch the ISC, if RPM does not, cut in half,(1/2) or stall?, then at the same time ,turn the BLEED CW. (closing this last supply of air)
the RPM MOST FALL to 400 or stall. if not? there IS A LEAK (vacuum)
IF SAY IT DId, then the bleed was turn all the way out, letting in huge amounts of air.
usually when you have say a small air leak (vacuum) and idle is too high
and you start turning the bleed screw CW, at some point the ISC wakes up(its not pinched now) and idle Locks in at 800rpm , regulating.
The bleed screw can hide some small leaks, (with in the range of the bleed, and ISC)
but most leaks get worse in time, and above is just a band-aid to nowhere...
once i get an engine running right ,not misfiring, or bogging, i do this test (pinch) and bleed checks,per above
before doing any duty cycle tests or precision spark timing. (timing needs idle near 800 +freeze jumper)
if there are no major leaks , i then do the duty cycle calibration and for sure, on all new Throttle-bodies.
and we have a cheap meter that works now. off ebay.
i just tested it from 5v to 18v and a wide ranges of ISC frequencies (or is 200hZ) it works great.
keep in mind all 8v engines make full power, with vacuum leaks, the engine might scream and make huge power when the iSC looses control.
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