Hi everybody,
This car's driving me crazy. I won't bore you with the long story, but here's my current problem: CO emissions are too high.
What I've done to the car so far (some for reasons other than emissions):
-new air filter
-new spark plugs/wires
-new distributor cap/rotor
-new mass air flow sensor
-whole new engine harness
-I've run sea foam through it/ changed the oil & filter

car still won't pass marta. It runs great otherwise, but just won't pass. So I'm thinking maybe I need a new catalytic converter? What do y'all think? Anybody else had this problem/been able to fix it?
Any and all help is greatly appreciated!

 

did you replace the o2 sensor? Also not sure if that year allows you to adjust the timing or if its set by a position sensor. I'd probably start by checking ignition timing (retard spark =higher COs/lower Nxs, advanced = lower COs/higher Nxs). Also a vacuum leak can throw off the controls leading to an improper mixture so you should check vacuum lines and possibly do a smoke test to find any leaks. After that inspection I'd suggest the O2 sensor but you may wind up dropping the cat just to get at it (I had to drill one out of the cat on an Audi 4000Q ugh). If that's the case then you may want to do the cat as well. My money would be on the O2 sensor or a vacuum leak.

 

I have not replaced the o2 sensor (yet). It'd be easy enough to do though (it's right there in the engine bay on the exhaust/easy to access). Thank you very much for replying!

 

What causes high CO? Rich Fuel Mixture - SmogTips.com. Failed CO Emissions. Why did my car fail the emission test for high CO emissions. What is CO. My vehicle failed the emission test for high Carbon Monoxides. Why my car produced high CO. High CO f



What are the numbers for the other gases?

 

you're probably at end-of-life of your catalytic converter, we had to replace our 87 240's to pass smog a couple years ago. but, for sure, try a new O2 sensor first. make sure you use a bosch one. also, getting the car as hot as possible immediately before the smog test can help a marginal cat pass.

 

you could also try an 'italian tuneup' prior to going into the test

 

The last time I ran it through the numbers were as follows:
HC: 107 ppm (220 limit, so pass)
CO: 3.29% (1.2 limit, so fail)
CO2: 4.1% (no limit, so I'm not sure why they even include that)

 

Pierce, I'll try and go grab a new o2 sensor today.

Silvermine, what exactly is an "Italian tune up"?

 

driving it hard at high RPMs. like, 65 on the freeway in 2nd for 5 minutes.

 

Hope you have AAA. Sounds like a recipe for a tow-truck.

Have you checked your timing?

 

Yeah that seems kinda rough on the old girl. I haven't checked my timing, nor do I have the equipment/know how to do so. I think I'm gonna grab an o2 sensor tomorrow. I'll keep y'all posted.

 

Check this out:

HC goes down, CO goes up!

CO goes up, HC goes down! (looks like you have wiggle room on the HC).


I say you are running rich.

I need to learn more about C02 and o2%! I wanna say CO2% at 13% means complete combustion. Not sure what it means if its down at 4.1%..... feel free to school me on my CO2% reading skills! searching isn't getting me far very fast.


1986 is LH2.2+ignition box on the inner fender. I have heard of issues and tweaks here. Again, I need more schooling, but i wanna ask what your timing was on your most current report. They check it here in California. If you had advanced timing you would have high nox. Not quite sure what effect retarded timing has on the numbers. I should probably learn it! Your state may not check NOX readings...




A new cat will make all three readings go MUCH lower. HC, CO, and NOX. Hence why it is called a TWC (Three Way Cat) It knocks down the THREE pollutants! I plan to just put another fresh cat on. It has always worked except for ONE time!

 

one o2 sensor test is to check for voltage swinging back between .1-.9v. If stuck at either extreme=bad sensor.

 

 

I live in Davidson county in TN. Our emissions only check for HC and CO (at least in older vehicles). I've got a new oxygen sensor on the way today, so I'll install that and report back.

 

The required "PASS" numbers keep going down around here...


why are you just stabbing an expensive sensor at it?

 

Because from the research I've done on what causes the car to do what it's doing, that's one of the main suspects (bad o2 sensor). It reads how much oxygen is in the exhaust and tells the computer what mix to give the engine.

 

so what were the voltages on it when you measured it?

 

Alrighty. Installed new o2 sensor today, went through emissions. Still failed. Might see about a new catalytic converter tonight. Any other suggestions? Should I check my timing/is that easy?

 

Alrighty, so I bought a new cat today! Any suggestions on how to get the old one out? Those bolts are practically rusted on, and I've already goofed and rounded one off... I'm tempted to take a grinder to it and cut in the middle (where the gasket sits), then drill out the bolts the rest of the way if I have to.. Any thoughts? Btw thanks a million for the help so far!