NOx emissions '94 Merc Grand Marquis

I am trying to find easy, cheap ways to bring down NOx levels on a MA emissions test.
My '94 Grand Marquis wasn't driven from Nov. 05- June 06, and then July
06- august 06. Got it inspected basically the day I started it up again in August, and it failed MA emissions for HC (read 1.21- limit 1.20 gpm) and NOx (read ~4.00- limit 2.50). I have driven the car regularly for the past two months, added fuel additive for a couple cycles, and put some oil system additive as well. I had the oil changed, with 15w-40 (heavier than usual), and had the PCV valve replaced as well as fixed a hole in the connector to the valve the day before reinspection (yesterday) and failed NOx again but much lower. It read at 2.87 gpm a limit of 2.5. Passed HC with a reading of 0. 67, so definitely on the right track.
I'm trying to keep costs at a minimum, and I'm wondering if the NOx would come down enough just by burning premium fuel or any other quick fixes. I wonder if since its pretty close I could avoid going in replacing things in the EGR system. I just want the car to pass inspection and serve me for another year at the most. Any tips would be greatly appreciated, thanks....
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No short cut here, check the egr operation make sure the passages are clear.

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On 15 Oct 2006 16:43:54 -0700, "will1234"

Your problem with Nox is likely plugged EGR ports in the intake. You can clean the by removing the throttle body and suing a scraper to clean the ports. They are under the throttle body and look much lok nothing more than some grooves in the surface. Those engines were known for this problem. You will need about an hour of time and a new gasket. I don't know of any way to clean it other than this. While you are at ir, be sure to cleanr your throttle body, IAC and MAF. There are sites with pics an the web to give you an idea and instructions on how to do this. If the Nox is not drastically reduced after you have completed this maintenance work, you may have to replace the DPFE sensor. Also, while you are in there cleaning things, make sure you check or, preferably, replace the tubing related to the PCV as it is also a common problem especially in the elbows. Once you get this take care of, your 4.6L V8 should have an almost breathable exhaust.
Lugnut
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Thanks for the help, I just have a couple of questions. Can I get to the EGR without jacking up the car, also can I just take out the entire valve to clean out the intake lines. I have a repair manual for the vehicle, but it deals with replacing the EGR valve entirely and not specifically cleaning the ports.
Thanks,
Will

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On 15 Oct 2006 18:47:01 -0700, "will1234"

No! You do not remove the EGR valve or even touch it. The ports in the intake manifold under the throttle body is where they plug. The EGR valve rarely fails or gives a problem on them. The lines are plenty big and do not collect any appreciative buildup. Unless you have a real oil burner, don't worry about the egr. Once you remove the throttle body you may have to look closely to see the cutouts in the gasket surface that serve as the egr ports if they are completely plugged as mine were. make sure you stuff rags or something into the intake to avoid some of the crap going into the engine.
Lugnut

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will1234 wrote:

To add to the excellent info Lugnut offered, you can buy a screened EGR gasket if you want to replace the original gasket. This modified part has a screen spanning the center to help burn and break up carbon debris before if plugs your EGR passages again. I would guess any auto parts store has them. I've even seen them at Autozone in the Help! Motormite display.
Toyota MDT in MO
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I had a mechanic clean out the ports, they were apparently very clogged. The car barely passed, right on the limit (2.50), but apparently the catalytic converter is operating at 5% efficiency. The car is now legal, which is all I wanted in the first place. I assume if the cat was replaced the NOx would go even farther down, but I don't really care. Thanks for the good advice from all. You all were right on the money.
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