Q-Jet Queries

[tellboy]

Hi folks , i need a 2nd or 3rd opinion as I keep 2nd guessing my self .
quick background update; elcamino 305, I've removed all the smog pump gear and installed headers with Co2 sensor in rh pipe line.
I've seamy rebuilt the 4barrel q-jet, new throttle positioning sensor, new mixture control solenoid and float system and are confident with float height etc.
The engine starts and runs easily but is running very rich, i.e black sooty plugs , black exhaust etc
part of the smog system had a vacuum line feeding off the front bottom of the carb T;d into the vacuum line that runs to the rh rocker cover.
if i block this air feed it runs a bit rough and idles lower , unblock it and it idles higher , still rich tho.
do i need to remove the small plugs and wind the 2 idle needles out to compensate or - have i got the main metering rods to high- or low , its got me buggered .
I've read a lot of the posts on here all ready but none quite the same so any input would be greatly appreciated.
cheers Guys ,

 

[MrSony]

Once you start messing with the CCC system it all goes to hell. It will run pig rich in limp mode. Its not a qjet issue per say rather half of the equipment is missing. Id put it back together and if it still does it check for codes.
Jump terminals A and B (top left 2 iirc) of the ALDL (obd1) plug with a paper clip with the key off. Turn it to run. Count the flashes. Should flash
Once then two quick flashes. Thats code 12 for diagnostic mode. It will do that 3 times then flash any codes the same way.

 

[Clone TIE Pilot]

Check your fuel pump pressure. Faulty mechanical fuel pumps can overpressurize the fuel and force the needle valve open, even brand new pumps can do this. Do you have any nozzle drip at idle? Generally you adjust the idle mixture with the idle air bypass valve on top of the carb.

 

[tellboy]

yeah, not quite as easy as that, all the old plumbing crap is in the bin, not sure what limp mode means , it runs and revs up fine just rich.

 

[tellboy]

nozzle drip? me or the car? dont know i"ll check both.

 

[jiho]

Maybe post-nozzle drip, 'cause it's allergy season.

 

[MrSony]

You may see the primary boosters dribbling at idle.
Do you got a check engine light on?

 

[fleming442]

Like MrSony said, messing with the CCC is an all or nothing deal, from what I understand. The system is either intact and functioning with the ability to troubleshoot it or it's not. It all needs to be there to work. If you want to remove it, get a non-CCC carb and distributor, then disconnect the ECU.

 

[pontiacgp]

Once you start messing with the CCC system it all goes to hell. It will run pig rich in limp mode. Its not a qjet issue per say rather half of the equipment is missing. Id put it back together and if it still does it check for codes.
Jump terminals A and B (top left 2 iirc) of the ALDL (obd1) plug with a paper clip with the key off. Turn it to run. Count the flashes. Should flash
Once then two quick flashes. Thats code 12 for diagnostic mode. It will do that 3 times then flash any codes the same way.

he removed the air pump and installed the O2 in the headers so he did not affect the CCC system. The air pump is only working during warm up

 

[Clone TIE Pilot]

O2 sensors need to be hot to work correctly. Headers can be too cool for ole 1 wire non heated O2 sensors, might want to upgrade to a 3 wire heated sensor. Do you have an analog dwell meter to see the fuel mixture dwell? A old OBD1 scanner like an Alltest Brainmaster would help too.

A common problem with Qjets is fuel dripping out the main nozzles at idle. Most common cause is having the throttle plates too far open at idle. This can be caused by not enough idle bypass air, not enough base ignition timing, or too much fuel like float or pump issues. New needle valves need to be tested with a Mityvac to ensure they seal, and fuel pumps must be checked for correct psi as it is common for new pumps to put out too much psi. Old pumps can also fail in a way that increases psi too.

Are you sure that you recentered the throttle plates correctly? Its tricky to recenter them after a rebushing job. If they are off center they can cause idle issues.

If the computer detects something major is wrong, it will go into limp home mode where it defaults to full rich and no timing advance.