92 no egr or codes fails NO emission

[fredjr]

my 1992 failed emissions testing

rd limit
HC 10.2 147
CO 0.47 1.64
NO 1663.1 930

It runs fine and I didn't anticipate this so the registration expires in 2 days and I don't have cash for repairs - was told to clean egr so I looked and there isn't one. however while looking I find in yellow paint stick writing 91 ford aero on the motor - so now I think motor was changed before I got the vehicle so the odometer of 152k doesn't match motor miles. Anyways I have no clue how to lower my NO emission level and very little time......

T.I.A.
Fred Jr

 

[Brain]

I had some problems (that I fixed without much $) with emissions lately...give me a couple of seconds and I'll get back to you.

Causes of High NOx readings:
High combustion temperatures -
High combustion pressures -

These seem to be good things other than they cause pollution...I bet you get pretty good milage per gallon of gas. It is correct that the Aerostar had the same (swappable) motor in it for certain years, but it is also possible that just a single parts was pulled and swapped in, like a head. That's what I did when I found out that I had a head with two cylinders that had cracks between the valves - '95 (or '96) Aerostar from a junkyard for $20.
Yellow paint pen markings are typical for junk/salvage yards, so it might be a case where your milage is correct for the engine but incorrect for that one part.

 

[Brain]

Here's the list of things that make for high NOx readings:
1-vacuum leaks
2-incorrect engine timing
3-inoperative/missing catalytic converter
4-faulty computer controls
5-incorrect carburetor adjustment
6-faulty EGR system
7-excessive spark advance
8-faulty thermostatic air cleaner system
9-engine deposits

 

[Brain]

Of these things you don't need to worry about #5 or #6 because they don't apply to the '92. #2 and #7 are basically the same thing and are run from the computer (#4 on the list), so if there aren't any codes you can't really do anything about that on the cheap either. I'm assuming that you do have a catalytic converter in place and that it is working, so #3 is off the list. That leaves us with #1, #8, and #9.

#9 is kind of tough to deal with because it is internal to the engine but basically the deposits take up space so that the compression is raised (compressing air/fuel mixture into a smaller volume).

#1 is a matter of checking for hoses that might be disconnected or are old and leaking. Maybe an auto parts store will let you hook up a vacuum guauge to your intake manifold to see if you have good or bad vacuum.

#8 is something that I noticed my '91 had a problem with...it was a part meltdown (but not really necessary in the first place). On the passenger side of the motor there is a shield that surrounds the exhaust manifold and a hose that comes off of it and connects to the cold air intake. Pull this crusty hose off and you can basically eliminate this issue from the list. It supplies warmed air (from around the exhaust manifold) to the air intake, which then goes through the filter and into the intake air supply. The '91 had a melted thermostatic air mixing valve. There is a vacuum line that runs this valve, and while you are looking there, you might want to see if that is a cause of any vacuum leaks.

One other reletively cheap thing to try is to change the thermostat. The stock part is 198 degrees, but they make them (same price - different model number) that opens at 180 degrees...

Maybe sombody else here can give some ideas on engine deposits and correct anything I might be mistaken about. I was trying to give some things that can be done for less than $10.

 

[fredjr]

thanks for the info - will remove the hot air intake. I think my cousin has a vacuum tester so I will try to find any more leaks this evening - found 1 last night and replaced the fitting - I just put in a new thermostat also - should have mentioned it was tested with thermostat removed and that did lower the NO emissions from 1973.4ppm to 1663.1ppm

 

[liqhx2]

run a can of sea foam through the intake and also in the gas tank

 

[MrShorty]

From what Brain wrote, I gather that high NOx can be caused by many of the same things that cause this engine to ping under load. So I would suggest you do some of those same things.
Run a decarbonizer (like sea foam) and hopefully take care of #9
Check for vacuum leaks (#1). One common vacuum leak on this engine is the lower intake manifold gasket. You can usually just tighten it to spec (the bolts come loose).
Similar to a vacuum leak, in that the computer doesn't "see" all the air coming in, is a dirty MAF.
And, one last note about #2 and #7. Even though the timing isn't adjustable, you can verify base timing and timing advance. See ignition timing tests at www.dalidesign.com/hbook/eectest.html I almost never hear of timing problems on the EDIS system, though, so I doubt this is an issue.

 

[Billy177]

clean the maf