Qjet idle problems!
03-06-2001, 03:27 PM
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Qjet idle problems!
I just rebuilt and installed a Qjet from a 1975 olds with a 350 on my car. It runs really well on the main and power circuits but i cant get it to idle right.
I smells very rich and i cant get it to pull decent vacuum unless the idle screws are out 2->2.5 turns. When they are out this far it idles at about 900-950 with the stop screw backed off all the way. It pulls 19" vacuum like this which is about 1" less than the holley i just took off.
This carb has an APT in it which i suspect may be the problem. When I disassembled the APT for cleaning I counted the turns in it so its close, but may be off by 1/8 turn either way. How does adjustment on this work and how does this circuit work? I was under the impression that it leans the engine under low load conditions (such as idle?)
I have to go through emissions this month (sniffer only) and therefore need to get this remedied.
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1984 Z28 (L69) monochrome tangerine orange with IROC decals and hood
1987 IROC wheels with Goodyear GSC's
305 from 87 IROC with 1994 LT1 cam (203/208 .450/.460")
performer intake with holley 600 (#1850)
Qjet is in the works
dynomax cat-back
non WC T-5 with 0.73 5th
3.27 nine-bolt
I smells very rich and i cant get it to pull decent vacuum unless the idle screws are out 2->2.5 turns. When they are out this far it idles at about 900-950 with the stop screw backed off all the way. It pulls 19" vacuum like this which is about 1" less than the holley i just took off.
This carb has an APT in it which i suspect may be the problem. When I disassembled the APT for cleaning I counted the turns in it so its close, but may be off by 1/8 turn either way. How does adjustment on this work and how does this circuit work? I was under the impression that it leans the engine under low load conditions (such as idle?)
I have to go through emissions this month (sniffer only) and therefore need to get this remedied.
------------------
1984 Z28 (L69) monochrome tangerine orange with IROC decals and hood
1987 IROC wheels with Goodyear GSC's
305 from 87 IROC with 1994 LT1 cam (203/208 .450/.460")
performer intake with holley 600 (#1850)
Qjet is in the works
dynomax cat-back
non WC T-5 with 0.73 5th
3.27 nine-bolt
03-08-2001, 11:33 AM
#2
Supreme Member
The APT doesn't affect the idle. That's part of your main circuits that don't kick in until you're beyond about 10% throttle.
2 1/2 turns out sounds pretty good, actually, on the idle mix screws. Many stock carbs you have to put them 4-5 turns out and STILL can't get it rich enough.
The high idle is either from over-advanced ignition timing (like running vacuum advance hooked directly to a full manifold vacuum source) or from a vacuum leak either inside the carb somewhere (worn throttle shafts) or from someplace on the intake manifold.
2 1/2 turns out sounds pretty good, actually, on the idle mix screws. Many stock carbs you have to put them 4-5 turns out and STILL can't get it rich enough.
The high idle is either from over-advanced ignition timing (like running vacuum advance hooked directly to a full manifold vacuum source) or from a vacuum leak either inside the carb somewhere (worn throttle shafts) or from someplace on the intake manifold.
03-08-2001, 12:11 PM
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The engine idled OK with the holley, so i know its a crb prob. I am wondering if the needle/seat is leaking because I have a holley "red" pump with no regulator? I am going to pull the carb off tonight and take a look.
THe dist is hooked to the port on the front lower right which has no vac at idle (i checked).
------------------
1984 Z28 (L69) monochrome tangerine orange with IROC decals and hood
1987 IROC wheels with Goodyear GSC's
305 from 87 IROC with 1994 LT1 cam (203/208 .450/.460")
performer intake with holley 600 (#1850)
Qjet is in the works
dynomax cat-back
non WC T-5 with 0.73 5th
3.27 nine-bolt
THe dist is hooked to the port on the front lower right which has no vac at idle (i checked).
------------------
1984 Z28 (L69) monochrome tangerine orange with IROC decals and hood
1987 IROC wheels with Goodyear GSC's
305 from 87 IROC with 1994 LT1 cam (203/208 .450/.460")
performer intake with holley 600 (#1850)
Qjet is in the works
dynomax cat-back
non WC T-5 with 0.73 5th
3.27 nine-bolt
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