Failed emission test

95 chevy pu 4x4 350failed emission test, the codes or #'s are hc 3046 co 2.48

How many miles are on it, what did the testing facility say, how’s the maintenance been, how has it been running, and what have you looked at so far.

what weight is this log.?

what state?

eng? ect ect

OP, if your unburned hydrocarbons and you carbon monoxide readings are too high it indicates that the combustion of your fuel is incomplete, often due to a rich mix or poor ignition. There are a myriad of possibilities that can cause this from oxygen sensor problems to a way overdue tuneup. With more information we can perhaps help, but without it the task is impossible.

about 130 k the facility never says anything in my state nj just you failed.maintenance ok runs fine. problems are muffler little loud prob. need new muf.when returns to idle almost konks out I’m thinking maybe cat is cloged? just tuned up & o2 sensor just replaced.

replied to your first question 02 sensor changed, I think cat is cloged?

At least you won’t have to clean the litter box.

Okay, that wasn’t that funny, but if your catalytic converter is clogged, I think you would notice other symptoms.

Is the check engine light on? Perhaps you should take it in for a professional diagnosis. I doubt anyone can help you without the detailed information found when properly diagnosing the problem.

You have to take care of the CAUSE of the problem. If it has a clogged catalytic converter, or a carboned up oxygen sensor (Yes, I know you changed the oxygen sensor), that is caused by a poorly tuned engine.
Tune the engine with fresh spark plugs, maybe wires, air filter. Then, get the check engine light codes by flipping the ignition key ON and OFF three times (end up with key in ON). Count the flashes. Each code will be a two digit number, such as:34. Then, tell us the code for fix-it ideas.

I would expect the HC spec for a 95 to be about 120ppm with a CO of about 1.00

You are running extremely rich but your high HC is not caused by a lean miss-fire or way to high CO although your CO is high.(unless you consider a vacuum leak induced miss-fire a lean missfire)

You have a problem before the cat (high HC are primarly secondary ignition related,next mechanical engine problem, then lean miss-fires, anything that is preventing the fuel from burning correctly or at the correct time.)

Your vehicle is called a “gross poulluter”

A clogged converter typically would cause noticably poor acceleration and power well before it got to the point of causing high CO and HC.

Good point about the CEL. And the need for diagnosis hands-on. I agree.

I agree that lean operation is not appliable here.

High HC and CO are both symptoms of either rich operation or and/or incomplete combustion. Lean operation I’d expect to cause increase cylinder temperatures and resultant high NOx readings combined with perhaps preignition.

I agree with Whitey that this needs a hands-on look-see.

With HC that high, I think you have a “dead hole”

You don’t hear any type of miss? Ohe of the cylinders isn’t hardly firing or not at all. You must be able to smell the raw gas coming out of the tail pipe? Is this carburated? If so, there is a problem somewhere. I bet your gas milage is horrible!

No check engine light on. that seems wierd since it failed emissions.

I agree sure smells bad.

Outstanding! I’ll get the codes & get back to ya. Thanks.

Could my ecm be going bad?

That would be the absolute last item on my list of things to check. First items would be, since the CEL light isn’t lit and should be if it were ignition related, probably a leaky injector. If you have an injector leaking fuel into the cylinder rather than closing properly you’ll get rich operation symptoms. The injector is under constant pressure, so leaking causes fuel to be constantly fed to the cylinder.

1995 was a bad year for GM ECMs. A lot came with ODB-II-style computer connections on a quasi-ODB-I programming. The ODB-I system did NOTHING to monitor emissions, and would not set trouble codes for a lot of problems connected to emissions.

That said, I’d have the fuel pressure checked, and have the fuel injectors evaluated for leakage. A bad regulator or leaking injectors would cause an over-rich condition, and be missed as a problem with this ECM.

Well went out & tried to get the codes but it would’nt give them up.I do remember when I took it in to get ready for inspection my mechanic said the computer had an open loop? so they changed the 02 sensor, said computer wasn’t controlling feul mixture but should be fine now.They don’t have an inspection license so for reinspection I can’t use them. Ran fine till I got home & then started with the almost konking out sindrome, I guess the computer went back to it’s old tricks & I just checked for missfiring & no misfires.Maybe the computer is on it’s way out? This happened after a 6hr. run back from VT.

Would that apply to tbi also?, I mean concerning the injectors.