Z-man

Yeah - your bud was messin' with ya. motor RPM's are the same whether you have stock tires on your car or wagon wheels.

Calmchaos - you may have a fouled catalytic converter.

-Z

Calmchaos

I better not, that cat only has 10K miles on it. And it was one of those ~$400 ones.

Also still not 100% on testing the O2 sensor if anyone can clear that up for me. I know two of the pins are for heating the sensor with 12V. So I assume I stick the meter on the pin that doesn't heat it and then a ground.

Mike C.

On the single wire O2 sensors there is only a single connector (it isn't coax). The test is done with the sensor still bolted to the exhaust pipe, which makes a ground connection to engine block. I guess you could clamp the volt meter probe to the body of the O2 sensor.. one way or another ya gots ta have 2 connections to read a voltage.

Calmchaos

Yeah I think I'll try it with one end in the sensor, and the other either on the engine block or on the neg of the battery.

Calmchaos

Hot on the trail.
I tried it the way specified above and the sensor read between .78 and .83V at all times. I disconnected the vacuum hoses Clarks Garage said to, and ran the car at 2500. I saw no change in the voltage.

So... I guess this means the O2 sensor is bad. LOL
I'll also be flow matching my injectors by sending them to SouthBay Fuel Injectors, and buying slightly hotter plugs.

Hopefully that will get my HC and CO to pass.

Calmchaos

Ok, I just went back again yesterday, and it failed again. I had my injectors flow matched and resealed, and I also replaced the O2 sensor with a 3 pin universal Bosch.

The emissions went way down to the point that I passed on the HC, but I still barely failed on CO. My new CO level was 0.83 (need .50) to pass. You can see the first results on page one.

Any more ideas for me? I ran the car for a good long time so I know that it was as hot as I could get it when I went through.

nickg

change the plugs, change the oil and chck the vacum lines for leaks. take the car for a good drive, make sure it is HOT when inspected. CO isn't really gonna change much with a new cat, did you ever mess with the adjusting screw on the AFM? (is the plug missung?)if so that is your problem....get a untouched used one and swap it in. (to correctly adjust an afm you need a 4/5 gas analyzer and the SKILL to do so) has the Throttlebody been messed with? (idle speed? people oftem adjust the minimum air screw to set idle not knowing that this screws the Throttle switch) does the throttle switch work?

nickg

oh..one more thing, running a good top engine cleaner like gm top engine clean or seafoam will clean out the cat as well as make the car run alot better....gm also has a REALLY good throttle body/intake plate cleaner...do that too

Calmchaos

Cool. Thanks for the info.
The plug on the AFM is still there so that was never messed with.
Throttle switch is basically new (only a few thousand miles on it). The throttle body was off recently when I resealed it, the screws haven't been messed with (by me anyway).
Would anything that affects the idle really mess with the emissions at around 2400-2500 rpm?

I'll try some engine cleaner, put some new plugs in it, and change the oil. I've checked the vac lines over and over, but I'll check them again.
Why do you suggest changing the oil? Curious.

nickg

fresh oil will not burn as easily as there is no fuel in it...and that will lower your HC
adjust the throttle switch according to the manual, this is more likely the source of the problem(throttle plate adjustment)
you can verify that it is correct by pinching the various tubes and seeing if the idle changes

look at the action of the afm and make sure it has a clean even sweep with NO binding or sticking. verify that your fuel pressure is correct. check the coolant temp senser as well with a dvom and hot water, it should evenly change resistance
do you have an oiled gauze filter? k&N? if so, toss it..you may have over oiled it and that would cause the problems in some cases. put a fresh paper filter in
any other mods? coil or msd? a weak coil will cause this

DarylJ

I'm trying to follow the logic through on this one.....CO is a product of combustion. A weak coil may not get you full combustion. So how would a weak coil increase your CO? HC, sure...that makes sense to me. But I don't get the CO part.

Calmchaos

Ok, so I took the plug out of the AFM that covers the AF ratio screw.
The thing was half stripped which means someone messed with it before I got it, and they didn't know what they were doing.

What I did was run the car up to temp, then hooked up my voltmeter to the O2 sensor. I got a base reading of .88V which is on the rich side. I backed out the screw until the O2 read .02V indicating a lean mixture.
Then I took the screw back in a bit. Now the sensor reads very close to .8V. I think that should be close to an even mix.

Does this sound like it's worth going through inspection again?
Spark plugs have also been replaced.

Calmchaos

bump

nickg

co is a function of mixture. a rich mix will give high co...but so will a weak coil. secondary combustion in the cat(from the fuel heavy combustion) will cause co to be out...it will also make the cat glow. what happenes inside is incomplete combustion, the cat can only do just so much

as i suspected, somone messed around with the trim screw. sounds like you got it, you can do it the old fashioned way , use a vacum gauge and adjust the screw to give the highest vacum at idle...I never understood why people messed with that trim screw, unless they had a gas analyzer, they could not get it right(reading the oxy senser will get it close)

DarylJ

That make more sense if there's secondary combustion. Thanks for the explanation.