3.2 smells kinda rich at idle

[c2 rower]

PO removed the CAT. I replaced the O2 sensor, which goes in the bypass pipe. Has Steve Wong chip. Car runs great, no flat spots, smooth idle. It's just that at idle it smells rich. My wife finds it annoying. Can the CO be adjusted without the CAT? BTW, In here in NY they do not do tailpipe testing.

Has anyone ever tampered with there anti tamper plug and tweaked the CO adjuster on the air Bosch air volume sensor?

[Steve W]

When you remove the cat, it is normal to smell more of the exhaust, because the cat typically burns and hides almost all of it, including burning oil. It is pretty easy to adjust the idle with the CO adjuster as you found. Just remove the plug and turn the screw to adjust the idle mixture. Using a long 3mm hex wrench, turn counterclockwise to lean, clockwise to richen. Reading the voltage off the O2 sensor helps and adjusting it to average between 0.2 and 0.7 will get you to 14.7:1 stoichiometric.

[Lorenfb]

Put the stock chip back in and test for the rich mixture smell.
To attempt to get improved performance, many chips over-richen
the mixture which many have reported on this forum.

Contrary to fact, most don't realize that the air flow meter adjustment
screw is only for the idle mixture and has NO affect off idle when driving.
Your engine will most likely still run rich when drivng.

There's always some tradeoff or headache associated with those
performance chips!

[ben parrish]

When I removed my cat I also found the idle exhaust to be very strong with the stock chip. When I changed chips(Steve W) the exhaust didn't smell any differnt so I adjusted the idle mixture quite a bit to get the exhaust within acceptable limits for me. As Steve said, the cat burns off quite a bit of the odor. You have to decide for yourself if the smell is worth replacing the cat if the idle adjustment doesn't do the trick. I have always wondered if the cat was really restrictive enough to make that big of a difference in power. The car sounds deeper with it removed and there was a perception of more power but I really don't know how much power it adds by removing it.
Good luck,
Ben

[Por_sha911]

Originally posted by Lorenfb
Contrary to fact, most don't realize that the air flow meter adjustment screw is only for the idle mixture and has NO affect off idle when driving.

Loren: Let me make sure I understand what you said: the fuel/air mixture adjustment screw under the air flow sensor ONLY affects the mix at idle?

[Joe Bob]

As one who has just rebuilt an engine that went lean at WOT....I would NOT reccomend futzing with an engine's fuel management....unless you had an exhaust analyzer available....

[alf]

I am a little confused. Is the CO adjuster screw the same thing as the idle adjust screw?

alf

[Lorenfb]

Yes, the mixture screw on the air flow meter (different from the air screw on the
throttle body) only affects the idle fuel mixture. If you inspect the air flow meter,
you'll see that the mixture screw and its' air passage bypasses the air flow meter
"flapper".

When the engine is at idle the "flapper" is essentially fixed in a position and as
such the DME maintains a constant injector pulse width (fixed amount of injected
fuel). As more air bypasses the "flapper" thru the other passage, it causes the
"flapper" to move toward it's rest postion (lean condition). This causes the DME
to reduce the injector pulse width leaning the mixture.

At off idle RPMs, the air which bypasses the "flapper" has basically no effect
on the mixture because of the volume of air flowing past the "flapper"
compared to that which flows thru the air bypass passage.

[fintstone]

Are you sure it is rich smell? A car without a cat always smells worse to me. As you know, the cat is there to clean up the exhaust ...basically to convert carbon monoxide (bad stuff) to safer carbon dioxide..but also cleans up other gasses too. Make extra sure you have plenty of ventillation when running a car without a cat.