Ever fail emissions with a mac (cat) h-pipe?
 

Went to emissions with my 95 GT and failed for nox. I was just about double the allowed limit. The car has 60k and motor wise its pretty much stock, full exhaust,with the mac (cat) h-pipe, pulleys, maf. The timming is set about stock, 11. I was told that the 2 main reasons why a car fails for nox is eiter bad cats or carbon build up. I doubt its carbon, but if it failed because the 2 cats wernt enough that pisses me off!! Anyone else have this problem??

Hope this helps. I had the same problem with a stock-H Pipe. NOx was double the allowed limit. I had everything tested cept for the CATs and decided not to get a new pipe, I retarded the timing from 15 to less than 6 degrees(not sure the exact, it was done by the shop). Then it passed. 92 GT 80K miles. They said they tested my EGR and it was fine, but now I am getting error codes saying EGR out of range.

Scott

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1992 GT 5.0L Convertible
BBK Shorties, Flowmasters, Super Chip, Mass Air, Under Drive Pullies, Hurst Shifter, Duck Tape
AIM: SmokeyDP

I run mac long tubes with high flow cats and my car fast passed. It suprised me considering my car is far from stock with an non emission cam, ported heads, intake, vortech s trim pullied for 12 psi and 38# inj. I was very pleased to say the least! Sorry to hear about your troubles. Maybe its in the tune.
Tom

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Vortech Supercharged 89 LX
Best run on dunlop radials 11.58 @ 126.5 mph!
Best run on hoosier quick times 11.15 @ 128mph!

Dunno what the problem is bro. http://www.mustangworks.com/msgboard/frown.gif When I was working there I ran my car through and I passed no problem. 90 GT offroad h-pipe and borla catback with 150k miles on it. Guess mine is just a clean running car. When I worked there, they said changing the oil will help pass emissions testing. You really should have no prob with a 95gt and mac hi-flow cat hpipe. Try changing the oil I guess. May need it anyways.

Keeping the car in general good tune will reduce emmisions, oil being one of those things. The plugs, ignition system, fuel injection, etc. being in good condition will all help reduce emmisions. Check all of those, but if you are really that bad, have you gotten a check engine light lately? Maybe your oxy sensors are bad....

Hey Ry95GT
I have a 95 gt and never had any problems passing emissions. I just thought you might like to know that I work at Jiffy lube and we offer a fuel system cleaner we hook up to the car and it cleans the emissions up really well. I did it to my car for the hell of it and it runs alot better too. We have had a lot of people come in who failed emissions, had that service done and then go back and pass, you may want to give it a try. I'm pretty sure it has a money back guarantee with it too.
Scott


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95 Red Mustang GT
Pro 5.0
Mostly stock(looking to modify)

NOx is caused by your combustion chamber getting too hot. EGR is primarily geared toward reducing NOx emissions. By recirculating exhaust gases back into the cylinders it reduces the temperature of the combustion chamber and reduces NOx emissions.

What kind of gasoline do you normally use? If you tested with 87, try going with premium. If you always use premium, that might explain the carbon build up. Run 87 for a while.

What kind of spark plugs are you using? What's the gap?

Do you have any other modifications that you forgot to mention like an adjustable FPR?

Is your air pump working properly and all the plumbing in tact? Your cats really need air to work efficiently. I really don't think it is your cats. Hi-flow cats are better than the stock cats, flow-wise and clean-wise.

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351W 89 Mustang GT Convertible

Im pretty much anal when it comes to keeping the car tuned, always doing everything on time. Oil was just changed 3 weeks ago. I always use premimun gass. Plugs (Motorcraft) are about 1 1/2 years old with about 5k on them. They are gaped at whatever the factory recomendation was. I havent gotten a check engine light so I dont think its the oxygen sensors. Im gunna try and retard the timming alittle more and go for a longer drive before I take it to the test. I went from work to the emissions place wich was about a 8 min drive and sat idling for about 15 min before they tested it.

Pull the plugs and check them, make sure that it really is running well. Like jimberg said, try lesser fuel, why are you running premium? with stock timing, I run regular and I've never had detonation or anything of the sort.

[This message has been edited by dinomite (edited 04-02-2001).]

I passed the Ohio emissions test with mac hi-flow cats.Holley heads &intake,24lb injectors
mac full length headers, timing @16 deg.btdc,
Sunoco 94 octane. I always run on the highway for a good 20 mins before testing. I don't know why but it helps.