I am trying to find easy, cheap ways to bring down NOx levels on a MA
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....
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.
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.
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.
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!
Toyota MDT in MO
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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