Dewey316

I tood my car through the sniffer today, and i failed for total hydrocarbons.

my question is what would i need to do to fix this, would it be my cat? or something with the engine.


TAI.
John

F-BIRD'88

High hydrocarbon reading means unburned fuel in the exhaust.
I'd look at the ignition system, oxygen sensor and the cat.
Also change the oil. Stop and go city driving causes the oil to become fuel saturated in a short time. Then when the motor
gets warmed up (during the test) the fuel vapours from the crank case are sucked in to the PCV and create a rich mixture.
If NOX was real low than the mixture is rich, if NOX was high
than the mixture is too lean and my be randomly mis-fireing.
Hope this helps.

Dewey316

OK my NOX was really low it was at 1.05 and the THC was at 2.66 so that would mean i am running rich then?... how do i correct this on a computer controlled car?

Vader

Dewey,

Make sure the oxygen sensor is operating, and if it is more than 30,000 miles old, replace it. You should also make sure the A.I.R. system is not leaking air into the exhaust manifolds. This will "fool" the O² sensor into thinking the mixture is lean and cause the ECM to enrich to compensate. Any leakage or holes in the exhaust near the engine can do the same thing.

Once you have a good O² sensor installed, try it again. You should be able to tell the difference by gas mileage alone.

It also helps to have the engine and cat converter fully warmed before you run through the test. The extra heat helps reduce HC levels by forcing more complete combustion, and the low NOX numbers could mean you are running a little too cold in the chambers as well. If you have a colder than stock thermostat installed, it could also be contributing to the problem. If you have a different fan control to help cool the engine, disable it or set it higher to get through the test lane. More engine heat is going to help you get through.

Dewey316

OK, well i put it new plug wires tonight, and i cleaned all the terminals on the distrubitor cap, hoping that will help the cumbustion. when i took the test, the engine was running about 180*-190* and i drove it for about 20 miles before the test. i also got a new O2 sensor tongiht, but could for the life of me get the other on off??? cause i have had the car for about 50K miles, and haven't touched it, and who knows how old it is. if anyone has any tricks for getting the O2 off let me know, cause i spend about 2 hours cursing, trying to get a wrench in there.

also, does running a higher octane gas help THC??? cause i am out of gas, so i am going to fill up tomorow before i run it through again

thanks for all the help, i gotta get this thru by thursday :-(

NEEDAZ

I failed on HCs, and got me the pass. Back off on base timing, for me I went for 6* to 1* BTDC. Then add three or four bottles for that dry gas into about a half tank of gas. This got me the pass with a hollow cat. This is if you JUST want to pass, not if you want to fix what’s broken.

88'camaro305TBI

iTrader: (2)

Here is a pretty much guaranteed way to pass. Me and my friend bought 2 brand new cats at a local store (the cheapest ones) and we installed them just for the emissions testing. I also put rubbing alcohol in the gas tank and the car passed with 0 emissions on 2 of the tests, and very low on the 3rd test. And that's with a rebuild 406. I don't know how much the rubbing alcohol helped cause my friend put that stuff in his Nissan Altima and it still didn't pass, so i'm pretty sure the brand new cats is what did it. If you don't have access to a welder or know someone that does, then that might be an expensive option for you.

Vader

Apply penetrating oil on the sensor threads as soon as you can - and keep it wet over the course of the day. You can unplug the lead, then get a box-end wrench on the sensor. Heat helps as well, so either a hot engine or propane torch can get the threads moving. At 50,000 + miles on the sensor, I would guess that it is pretty dead.

Higher octane fuel will not necessarily help, but alcohol blended fuels should (that's why all the additives help - but why pay for those when gasohol is already 10% alcohol?). There are fewer hydrocarbons to begin with, so there should be fewer out the exhaust. The alcohol also helps lower the combustion temperature, keeping NOX a little lower.

Your test temperature should be adequate.