Ok, well I recently bought an 87 GT and im working on getting it past emissions here in Arizona

My first test is

1.30 out of 1.60 HC g/mile - Pass
25.76 out of 15.00 CO g/mile - Fail
3.35 out of 2.50 NOX g/mile - Fail

So im thinkin to myself check the EGR for the NOX seems to operate normal, car will stall out if i pull it up manually and it holds vacuum if i pull it up then plug it all seems well, so I decide to check the catalytic out since the car had been sitting for a while before i got it I decided to pop the cat off even though it wasnt rattling the things EMPTY not even a sign of left over guts.

I replace the cat with a new magnaflow I had thinking woot problem solved ,

My second test is

0.36 out of 1.60 HC g/mile - Pass
3.48 out of 15.00 CO g/mile - Pass (drastically better I might add) Was kinda thinkin it might be running rich prior because of the high CO's but the new cats taken care of that
2.89 out of 2.50 NOX g/mile - Fail FAIL

So now Im sitting here still failing NOX while passing the others flawlessly

Now Ive got the awesome front manifold exhaust leak which might be an issue allowing oxygen in to the exhaust pre cat but i would think the computer would try to richen it up if its seeing lean an that would cool the cylinders a bit on its own resulting in less nox id think.

My other problem is the car is an automatic with no 2nd gear and I certainly hope not but im thinking the extra load on the engine being in 3rd more often is heating up the combustion chambers more then normal and causing my high NOX.

EGR system seems fine, no codes, and if the car stalls and bogs when manually actuated I would think its probably not clogged ( removed the valve only an all appears clean and carbon free )

No noticable vacuum leaks no high idle car runs very smooth.

Feeling like Ive checked everything at this point but im sure theres something stupid im overlooking that may help squeeze it through for now since i cant afford to replace the trans if thats likely my issue and i dont want to put much into the trans anyways since i have little plans to keep it and the 2.8 in the car.

If anyone has some tips or tricks or ideas feel free help out !

High NOX is caused by running too lean as well.
Dirty fuel injectors or an O2 sensor reading wrong can cause you to run on the lean side. Ignition timing could be advanced a little too much.
Just because the EGR will stumble the engine when operated manually and the EGR solenoid isn't setting a code, doesn't really me it is working.
The vacuum line from the solenoid to the valve could be bad. Have you checked the EGR tube for cracks?

I would check the ignition timing, run some injector cleaner thru the fuel system, and fill up with Shell Premium than go back and get it tested.

I had high NOX a couple of years ago, and the front exhaust manifold leak. Repaired the leak
and passed the smog test. Thinking was that the leak affected the oxygen sensor.
87GT

timings not a bad idea, as its something I hadnt thought to check, Leans a possibility but given the prior CO lvl before the new cat It seemed rich if anything but its entirely possible still, I have a wideband o2 sensor in my turbo sunfire i could stuff up the tail pipe if it comes to it see whats its doing.

Any other suggestions? ghetto solutions to just get that last .3 grams per mile out of her?

Did managed to check the fuel pressure in the last hour it was a steady 38 at idle and stayed pretty close with a light rev, Ive heard 40 psi is the normal anyone know for sure? Id assume its good and the 2 psi difference is more then likely my harbor frieght chinese pressure gauge or just variation thats low enough to not worry about anyways.

Maybe retarding the timing a hair if its not off will help anyways anyone have any luck with that on a near miss situation like mine?

this is how I got several of mine to pass and you would think it would never pass running like crap but it does.
first off go get 2 rubbing Alcohol dump in to gas tank then fill with high test gas and run it for no less than 30 min.
second back the timing down to the point it will just not stall. then warm it up and go test.
never turn your car off before the test it will be rich if you do.
once you pass reset the timing so it will run right.
this is how they get cars to pass at service stations and charge you 500.00 to do it!
if this does not work you may need motor work soon!
Good luck!

this is just a sugestion that has worked in the past in Cali. where the test is harder to pass.

I didnt remove my EGR tube but it didnt look like it had any real rust on it just a slight surface rust, i figured it was probably ok since the car has no signs of vacuum leaks and doesnt respond to the "spray stuff to find a leak" methods but i suppose when i fiddle with the timing I can pull it off and check to be sure, Will the EGR activate with gas in nuetral if I rev it? Im not familiar with what parameters it activates under

Did you replace the plug wires? The coil wire is in definite need of replacement. I usually retarded the timing to get it to pass in the past. That usually solves the NOx problem.

Rolland

Have you replaced that cat lately? My 85 GT failed NOX badly because the cat was bad.

Yeah brand new cat and new wires

If it's a manual, put it in neutral with the parking brake on, rev it 2500 and feel for the EGR valve lifting. It might take 30 seconds but it should lift. If not, fix that. You can't do this on an automatic without it being in drive. That is dangerous.

Had this same problem. Changing the timing will definitely help. Does the car have the low temp thermostat/fan swt in it. This wil also affect it. (Found out the hard way). Couldn't fix timing enough. Here in TX if it fails the 2nd time you have to pay again. I forgot to put in the 195 thermostat. Just a thought. 3rd time was a charm.

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Why fight to be accepted by people you don't actually want to be like?

Glad to hear you are having fun with the car. It does have a 160 thermostat in it, so you might try replacing it as well. I usually set the timing at 2 degrees for the test and as you can see from the previous tests, it passed just fine. Feel free to call or email me if you have any other questions and happy fieroing.

Rolland

Ah its funny you said you set it to 2 degrees because theres right where i stuck it this morning and she PASSED with flying colors.

Still laughin at myself a bit for completely forgetting to even think about the timing.

Thermostats deffinently on the list for replacement as well, not even so much because of the temp rating but its pretty erratic from the looks of it.

Appreciate the help guys.

GLAD it passed!

me too one less thing to worry about