Quadrajet Problem Solving > Diagnose a Quadrajet carburetor problem

High HC's on smog test.

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Chili Palmer:
A buddy of mine is running a stock rebuilt 401 in his Jeep CJ with a q'jet.

Here's the model number:

Carb is a Qjet, model is 7042210 QE
                                   1262
 
Here are the test results:

**********
2500 rpm test passed
O2 was 3.4
CO%  std is 5.00  test was 2.74
Hydrocarbon  std is 900   test was 403
Dilution CO & CO2   std is 6.00   test was 13.49
RPM was 2402
 
 
Idle test failed
 
O2 was 7.1
CO%  std is 5.00   test was 1.6
HC  std is 900       test was 1155  (this is what failed) (has to be less than 900)
Dilution   std is  6.00   test was 10.68
RPM was at 1130
**********

At first I figured it was old gas, poor timing, old plugs, etc. but here's what he's running..


Plugs look like brand new, gapped at .035, Champion the black ones
Coil is MSD Blaster
gas, is month old at best 6 weeks
temp was at 195*
plug wires are Accel high dollar wires
rotor and cap are clean and appear okay
dist is electronic
and have MSD-6 box on it

So it appears at idle it's not burning all the fuel (or is getting too much?) but at mid throttle it's working just fine. I've poked around some and read the float may need to be adjusted?

Any thoughts...?

Schurkey:
High hydrocarbon = lean misfire

When the cylinder misfires, the entire load of fuel goes into the exhaust un-burnt.

If you were too rich, your CO would have gone sky-high.  Not enough oxygen to convert to CO2.

Chili Palmer:
Understood on the HC's; any idea if it could be the carb and if so what could/should be done to fix it?

I personally have not touched it nor heard it run be he thinks it's a carb issue...

Any info would help - thanks.

Schurkey:
Did you ever adjust the idle mixture screws???

If I had lean misfire at idle--that'd be the first thing I checked.

Chili Palmer:
As in back in down i.e. lower the idle so less fuel is getting through?

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