Q-jet gurus - rich at idle?
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Junior Member
Joined: Jul 1999
Posts: 78
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From: Bootiful BC, Canada
Q-jet gurus - rich at idle?
OK, this is actually about my truck and FYI the carb is non-computer but is an emissions model. So, the basic deal is the truck starts and chokes fine but when it warms up (the choke plate opens completely) it sputters/stalls at idle. If you step on the gas it revs up great. I pulled numerous plugs and they are all sooty.
First I'll mention that a bunch of the emissions ports are plugged. These include EFE, EGR, the one at the rear which would go to the air cleaner, and external bowl vent which I later unplugged hoping to vent excessive fumes. PCV is hooked up and so is vac advance. Can those ports be plugged or is this my problem?
Other things I've checked are float level, curb idle adjustment, mixture adjustment (clockwise to lean), and I looked for an idle air bypass screw in float bowl but don't have one.
BTW I don't believe it's an engine/ignition problem cause it did have a 2 bbl carb on it before and ran fine accept I couldn't get the manual choke hooked up which made cold starting/driveability a real pain. Now I have an equally opposite problem!
So, I don't know if it needs to be rebuilt, the wrong carb for the application, or I'm just missing something.
Thanks for your suggestions.
First I'll mention that a bunch of the emissions ports are plugged. These include EFE, EGR, the one at the rear which would go to the air cleaner, and external bowl vent which I later unplugged hoping to vent excessive fumes. PCV is hooked up and so is vac advance. Can those ports be plugged or is this my problem?
Other things I've checked are float level, curb idle adjustment, mixture adjustment (clockwise to lean), and I looked for an idle air bypass screw in float bowl but don't have one.
BTW I don't believe it's an engine/ignition problem cause it did have a 2 bbl carb on it before and ran fine accept I couldn't get the manual choke hooked up which made cold starting/driveability a real pain. Now I have an equally opposite problem!
So, I don't know if it needs to be rebuilt, the wrong carb for the application, or I'm just missing something.
Thanks for your suggestions.
Supreme Member
Joined: Sep 2001
Posts: 6,111
Likes: 53
From: Ontario, Canada
Car: 1988 Firebird S/E
Engine: 406Ci Vortec SBC
Transmission: TH-350/3500stall
Axle/Gears: 7.5" Auburn 4.10 Posi-Traction
Remove the carb and look for the primary metering fuel wells
cast in the baseplate. The ends of the wells are plugged
with lead. These well plugs are leaking fuel causing the rich idle
and blackened plugs. You can repair them by cleaning all the carbon off them and spreading some JBWeld epoxy repair over the ends Let it cure over night, then reinstall the carb.
You'll have to replace the spark plugs, they are carbon fouled.
This is a common problem on QJets.
cast in the baseplate. The ends of the wells are plugged
with lead. These well plugs are leaking fuel causing the rich idle
and blackened plugs. You can repair them by cleaning all the carbon off them and spreading some JBWeld epoxy repair over the ends Let it cure over night, then reinstall the carb.
You'll have to replace the spark plugs, they are carbon fouled.
This is a common problem on QJets.
Thread Starter
Junior Member
Joined: Jul 1999
Posts: 78
Likes: 0
From: Bootiful BC, Canada
If a picture is worth a thousand words then... 
!!!
I tried your suggestion Fbird88 and that totaly fixed it! I thought there must have been something screwy because turning the idle mixture screws all the way lean didn't even help.
Thank you so much, I've been struggling with this for almost a month and I was ready to pull all my hair out!
Cheers,
Ted
!!!I tried your suggestion Fbird88 and that totaly fixed it! I thought there must have been something screwy because turning the idle mixture screws all the way lean didn't even help.
Thank you so much, I've been struggling with this for almost a month and I was ready to pull all my hair out!
Cheers,
Ted
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