[AF_mustang95GT]

I have a shorty headers, h-pipe w/hi-flow cats, and flowmaster mufflers. But I can't seem to pass inspection. I had a h-pipe w/ no cats on it so I switched it out but still can't seem to pass. Also the car is running a little rich. Any ideas on what is causing me to constantly fail?

[Julian Moore]

Originally Posted by AF_mustang95GT

I have a shorty headers, h-pipe w/hi-flow cats, and flowmaster mufflers. But I can't seem to pass inspection. I had a h-pipe w/ no cats on it so I switched it out but still can't seem to pass. Also the car is running a little rich. Any ideas on what is causing me to constantly fail?

The car is running Rich. DO some research, I know they make a few products to pour in your gas tank to pass emissions..and I know people who have had sucess. I have heard pulling an injector or even putting dry gas in the tank..burns cleaner. Check your fuel pressure, plugs..etc. Why is it not passing??

[Charles M.]

What's not passing is useful to diagnose what's wrong.

My '88 stock 5.0 failed due to high HC at idle. It was because of weak ignition at low speed, caused by old plugs. New plugs and it passed.

Another time it failed with high NOx at idle. That was because fuel pressure was too low. New fuel filter and regulator and it passed.

YMMV

[GTS5.0]

Man inspections must suck! None here!

[1995 Mustang GT]

if you had cats on it you may be able to pass inspection

[AF_mustang95GT]

The test said reason for failing is due to NOX being to high.

[meangreen92]

You want to change the oil soon before the test. Make sure the plugs, wires, cap & rotor are all good/newer. And clean/replace the air filter. If your timing is advanced, retard it back to the factory 10º BTDC. If you have a colder thermostat, change it out for a factory spec 190º unit. Make sure the car is warmed up, and don't use 91 octance gasoline. Use 89, or even 87.
Make sure the vacuum lines to your EGR and smog pump valving are all good. If it still fails, pull the codes.
You can try hooking the EGR valve straight to manifold vacuum, if the EVR solenoid, which regulates vacuum to it, is bad.
PM me if you have detailed questions, as I don't always visit the SN forums...

[AF_mustang95GT]

Isn't 91 a cleaner octane that would burn off better. I thought that was a better way to go than like 87 or 89.

[meangreen92]

If the octane is too high, it won't burn completely, leading to unburned HCs, and a higher HC reading. And oil which has been in the engine for a long time, causes higher HCs, because of unburned fuel blowing by the rings, and into the oil. This shows up in the exhaust as more HCs.

[AF_mustang95GT]

Ok, so that would be why im failing the NOX parts and in previous tests the HC's were to high also. So ill stick to a lower octane now, thanks.

[meangreen92]

I think that EGR is what cleans up NOX.

[AF_mustang95GT]

Ok, i'll check that out. Im gonna have it checked out with the computer to see if it throws any codes.

[302GT]

going of what I know oxides of nitrogen are caused by an overheated engine ,lean air-fuel mixtures, overadvanced ignition timing , or a defective EGR.

[1995 Mustang GT]

I think 302GT is right when i lived it texas thats what the inspector told me

[stevo1111]

You can back that down by getting a custom chip burnt to level out A/F ratios. I would only use that as a last ditch effort. Start off with a good tune up and make sure all the emissions functions are working as intended and that you're not running any codes as these guys have already told you. Good luck! I had to just deal with it and the only way I passed with all of my mods was a dyno tune and retarded timing.