Emission Problems & Possible Misfire

[En-g]

First post! Nice looking board! Hope someone can help :)

My car idles fairly smooth, the RPMs are pretty constant but it does sound like its misfiring. I took it in for an emission test the other day and it passed most of the tests but failed badly on HC @ idle. The limit is something like 300 and mine was somewhere around 520. I don't have the results infront of me so I'm just ballparking these numbers. Anyway the problem is unburnt fuel @ idle. So my question is what should I look at replacing/fixing to get this car to pass? Would adjusting the A/F mixture screw on the carb make a big diff? Any idea what could be causing the misfire? I changed the plugs and wires, but that didn't do much it still gargles when idling.

Would replacing the EGR valve help? Or does that just effect the NOx readings?

Any advice would be much appreciated!

[FyreDaug]

Im not sure about the emmision laws, but if your getting unburned fuel that seems to be a problem. Can you detect a misfire? Does it stumble on acceleration sometimes? Plus and wires is a good start, go next with a cap and rotor (also make sure your plugs are gapped correctly)

There is no AF mixture on our carbs.

I dont think changing the EGR valve would do anything, esp for a misfire (if thats what it is)

[En-g]

It does stumble a little at times during acceleration. One of the mechanics told me he could hear the misfire @ idle when standing behind the car. This is the last year this car needs to be tested too! :)

Isn't there an a/f idle screw on the back of the carb? I remember seeing this in another thread.

[shepherd79]

1. YES, there is idle mixture screw. but to get to it, you will have to remove the carb. take one braket off and pull out the metal plug. I wouldn't worry about it.
2. since you got your plugs and wires replaced, you should go one more step and get distributor cap and rotor replaced.
3. If i was you, i would take the vacuum pump and check the vacuum advance diaphram on the distributor. make sure they hold the vacuum. If it doesn't hold the vacuum, replace it. You may not be getting spark at the right time.
4. and the last thing i would replace if i was you, ignition coil. Just get yourself, regular coil (Accel, MSD, or just regular generic one).

i hope that helps.