Failed Emission Testing - Thoughts?
 

My 1992 5.0 Mustang failed emissions today for the first time since I have had it. Where I live we have to do it every 2 years.

It runs well and still has the factory h-pipe and catalytic converters. Based on these results what do you guys/gals think?

Thank you!

OK, I have tired to upload the picture a number of times...

how far off and for what measurent?

We have emission checks annually. My ‘95 911 failed the first two years, spent $1000 each year for my mechanic to get the numbers barely above passing. A Mech that works on older cars (356s) said to run a full tank of 91 ethanol-free gas through it. Refill again with the same and then make sure it is nice and hot and then get it checked. Passed with flying colors for the last 4 years. I know, completely different engines, but it’s the cheapest thing to try for a Pre-ethanol car. YMMV, I know mine does.

Tune-up

Running too rich or incomplete burning of fuel if I'm reading that right.
Start by checking the plugs for evidence of ignition or injector issues.
If the plugs all look decent and all the same, without any more info I'd suspect the O2 sensor.

Maybe not. New plugs would not hurt.

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Thanks for the advice so far. I will start with plugs, wires, cap and rotor. It is running well and I cleaned the mass air flow not long ago.

There is also a place near by that sells ethanol free gas, I will also run some fuel system cleaner through it and put the ethanol free gas in.

yes, do that & start with a tune up - may be needed anyway

then pull the plugs (again) and look at them

see if you can test the O2 sensor or just replace; hopefully you don't need new cat(s)

I am temped to try that to a couple of my cars even if there's no check engine light.

Yes fuel injector cleaner...

Have you had a look under the car? there may be one or two pedestrians jammed under there and that's messing up the air fuel ratio.


You're most welcome, I'm pleased to be able to help.

Oh, I have been under the car plenty. One of the main joys of old fox body Mustangs is adjusting the clutch fairly often. I have the fancy Steeda adjuster, just need to install it.

I put a bottle of Techron in it today and will run the tank low then add another.

My 1993 van barely passed emissions 4 years ago. This year I changed the plugs and air filter and it passed with flying colors.

fify

Change the oil too, that makes a surprisingly large difference, especially on hydrocarbons

Does it sit a lot? If it is just used for runs to the Piggly Wiggly, or to cars and coffee deals hunting pedestrians, but at low speeds, it will tend to gum Take it out on the freeway, or run it in a lower gear to get the cat hot. My understanding it that burns stuff off the catalyst. Italian tune up in the vernacular.


I like that soap and water wash it out thing Scotty does in that video.

Bad oxygen sensor can make it throw a cat code too

Porsche 356 Guru "The Maestro" The Late Harry Pellow once wrote about his trials and tribulations with the early California smog tests. He'd put a set of fouled plugs and dirty air filter in his old Mercedes and take it in for the test to intentionally flunk it. They'd give him the opportunity to make repairs and re-test, and if the re-test was marginally better they'd pass him. So he'd put a new set of plugs and a new air filter and pass with flying colors the next time. :D

It does not sit much, used to be my airport car (120 mile round trip all interstate) but now my daughter drives it in town and typically short distances. Once I get the plugs etc. I will take her (Farrah the Fox Body) out for a nice long drive. Cabelas is about an hour away on the interstate so I will get it nice and hot.

This isn't a cars and coffee mustang by any means. I prefer to scare all the pedestrians in my '78 VW Westfalia with its whopping 70 hp.

It is a bit more sporting using the bus, you have lot more room for disposing of victims, double bonus.

All of the above: complete tune up, change oil, plugs, and coil, and if you have the test values for O2 sensor, check it for resistance with multimeter, or just change the O2 sensor.