Yup. All I've done to it since then is on the last oil change switch to the semi-synthetic high mileage oil (10-40w) and oil consumption was slowed immensely. Still using some, but no where near the amount it was for a few weeks there.

One of these days I'm going to put some new valve stem seals on it.

Are you still running the same spark plugs from a year and a half ago? If so I think new ones would help.

and I will say it again, good gas is most likely the cheapest way to get by the test if everything else is up to snuff.

These weren't hack mechanics that were sending the mini van Moms to our place to buy race gas.

pull off a small vacuum line and let it leak vacuum at the manifold

If the cat is bad the EGR is not going to fix it

NOX is caused from combustion chamber temps to high. Pulling a vacum hose will want to lean it out and then the PCM will adjust the inj duty cycle by the 02 and adaptive fuel to compensate for it. And if you could get a large enough vacum leak to make it lean I dont think it will help as lean can make comb chamber temps higher.
I agree as its best to have a good tech look at all the sensors on a scanner or data recorder. I would want to know what the adaptive memories are running at as much the the 02 and by checking the downstream 02 reading (if it has one as I did not see what year it is) will tell how the converter is storing oxygen and it sets the goal of the upstream 02. But I did not see if its a 96 or older. If all sensors and adaptive memories all reaing in normal ranges you may just have to replace the cat.

You aready replaced the EGR valve which needs to be working right also. Dont forget if you test the EGR many use EGR valves that use exh system back pressure to let the EGR work so if the exh system is modded the EGR may not work correct. It most likey will have an EGR solenoid also that the PCM controls as it knows when to open the solenoid so it will pass vacum to the EGR valve. I would want to be sure the EGR is working. I have heard some say to put some dry gas in it and it may squeak by. Good luck , Ron

Years ago I had a car that didn`t pass emissions. I changed my oil. I put a couple bottles of dry gas in it and some premium gas and it passed on the next test. Maybe lucky I don`t know.

Your 1993 should have an OBD-I computer system.

Have you checked whether you have a code set for the EGR system by doing the key
On, Off, On, Of, On
Sequence and counting the flashes of the Check Engine light?

The EGR systems of 1992-1995 systems are complex.

The EPA required Chrysler pcm software to turn them on to fully flow maximum egr gas flow if anything went wrong. This "Full On when Failed" condition causes engines to easily stall out, prompting owners to get them fixed.

The EGR does not turn on until exhaust backpressure is more than 3 psi, which on the factory exhaust system is around 60% load.
There is both an EGR valve and a separate "EGR Modulating Valve".

The JTEC computer periodically tests whether the EGR system is working by waiting for backpressure above 3 psi and a fairly steady throttle. The computer then turns the EGR on and checks the O2 sensor to see if the air to fuel mixture slightly richens to less than 14.7
Then the computer turns the EGR flow off and sees if the air to fuel ratio slightly leans to more than 14.7

As rough rules of thumb:

NOx pollution reduces if the cylinders are cleaned out of carbon deposits so that the "Real World" compression ratio decreases.

NOx pollution reduces the higher percent ethanol in the gasoline mix.

NOx pollution reduces as cylinders get richer air fuel ratios.
One or more lean cylinders caused by partially plugged fuel injectors can cause a failed emissions test.

1992-1995 factory Dodge catalytic converters were so called "2 Way" devices that reduced HC and CO but not NOx.

1996+ catalytic converters were 3 Way devices that reduced NOx as well,
and so 1996+ OBD-II systems did not have EGR valves,
although their camshafts allowed more "internal EGR" during the overlap period.

Both 1992-1995 and 1996-2001 cat cons were very prone to break up inside and partially plug up, greatly increasing exhaust backpressure. There was a recall on this around 1998.
This high backpressure on 1992-1995 systems blew out the bellows on the EGR Modulating valve too.

....There is both an EGR valve and a separate "EGR Modulating Valve".

I was looking at this in the FSM, and it stated if anything went wrong with the electrical part of the EGR, it would go to full vacuum all the time.

On my old EGR assembly, the electrical was fine, it was the EGR itself that was bad, leaking diaphragm?

At this point, if not anything else, I fixed a vacuum leak I didn't realize the truck had. I continue to be amazed how much better the truck idles and runs now. I thought it ran fine before, but, often at idle, it sounded 'blubbery' (is that a term?) It lacked a 'crispness' if you will.

Now that blubbery' sound is gone, and its smoother than it was before.

I did the on-off key test to pull codes, and it only showed '55'.

Thank you 360view for that lengthy response.

The EGR Modulating Valve
Is the black plastic can attached to the EGR valve
by a larger black heat resistant hose (this is the backpressure sensing port)
And smaller vacuum hoses,
Plus an electrical connector.

On a Ram pickup it is on the passenger side of the engine rear.

On my 1995 i bought a spray can of Chrysler's
"Combustion Chamber Conditioner"
Pulled off the spray head
And pressed in a spray head from another spray can
That allowed me to spray through a small red extension hose (like WD40).

I then made the red extension hose twice a long by slipping on a slightly larger extension hose.

With the engine off i maneuvered this long extension hose down through the throttle body and worked it into one of the two left and right EGR discharge ports that are just below the twin butterfly plates. I sprayed and filled up this passageway cast into the aluminum "Beerbarrel" intake manifold.
(If i did this again i would have the pickup parked slightly uphill)

I waited 30 minutes to loosen up the carbon deposits,
got everything out of the way and started up the engine.
An impressively large cloud of black smoke came out the tailpipe for about three minutes. i suspect part of this black smoke was the Combustion Chamber Conditioner's secondary cleaning of cylinders after it got sucked out of the EGR passageways.

So much black smoke came out that i decided to repeat the process.

The second time the black smoke stopped after about a minute.
A neighbor walking by asked
"What in the world is wrong with your truck?"

I still had part of the can of Combustion Chamber Conditioner left,
so i pulled the backpressure hose off the EGR Modulating Valve and filled up that internal passageway, which the FSM shows going over to the EGR valve, up about an inch, and then down that metal tube over to its connection fitting to the passenger side exhaust manifold.
More black smoke after start up.

When you go back for the emissions retest, it might pay you to buy some E85 fuel and make a blend in your tank. 25 to 33% ethanol would probably reduce the NOx. Drive the truck for 3 to 4 hours so that the PCM computer's two memory positions called AFF and AAF "learn" the new blended fuel. AFF is the "adaptive fuel factor" for short term changes. AAF is the "long term adjustment" called the added adaptive factor.

There is a chance that this ethanol rich blend would partially dissolve some "gunk" in your tank and possibly load up the sock filter at the bottom opening of your submerged fuel pump/pressure regulator/gas gauge sensor unit. If your pickup has the original 1993 factory unit that sock filter may already have quite a bit of junk that it has caught over the years.

Mopar called the modulating valve the Transducer Vale. Many of the EGR/Transducer valve's also had the EGR solenoid made into the transducer valve. When you get a new EGR valve the transducer valve always came with it from Mopar. And even if it goes full vacum when it sees a problem it still needs the right exh back pressure before the EGR valve will open.Ron

Thanks for the responses everyone.....

I didn't get a chance to work on it as planned because the Wife's car crapped out (the 'new' car; 2014 ).

Trying not to complain as her car is still under warranty.

Is there a Kia mechanic in the house?

Throw a couple bottles of Iso-Heet in the tank and call it a day. Our standards are pretty tight in AZ and I've never had one fail when using Iso-Heet in the tank. 90+% Isopropyl Alcohol will work just as well. I was able to get my Demon through with a 284* 484" cam in my 340. It ran like crap, but I was able to choke it enough to get it through.

Change the oil and air filter before you go. Fuel injector/system cleaner like the more pricey Chevron Techron or Gumout Regane are some of the better stuff out there. Run a tankful of that before going again. This stuff removes carbon and crap in the injector. Works best on a long trip.

Another thing I have noticed since fixing the (vacuum) leaking EGR is that the truck starts better at first fire of the day. It never seemed to crank that much, but, if I cycle the fuel pump before attempting to start, I basically have to just 'bump' the key for it to fire.

I didn't mention it, but, I did change the oil and filter before going over.

Something tells me this is gonna be just like my old Caravan and not pass unless it has a new cat on it.

I'm still having troubles correlating what Hank posted about '93 cats being two way only when cat replacement always took care of the wife's NOx problems.

Robert

I would have tried the test again with a somewhat cooler engine and/or cooler weather. Heat makes the NOx.

dont screw with anything, put in a couple gallons of e-85 and it will pass with flying colors, did it all the time when I lived in Nashville.

Thinking about this again,
at those conditions of 1400+ rpm and low simulated pickup mph
It is not likely that the EGR has been turned on
since the exhaust back pressure would be low and less than 3 psi.

Much more likely that two or more cylinders are running lean.

If the truck is now idling more smoothly now that you fixed one vacuum leak, that is another clue that the air to fuel mixture in a few cylinders has gone from very lean down to still lean.

Under the file: 'what the heck was THAT?'......

Between the wife's car breaking down and me just not having time to work on it, I took the truck across the rollers one more time today for giggles.

Part of my reason for trying one more time 'as is' was because the convertor was definitely hot as I had just returned from Houston (40+ miles) and it was about 15 degrees cooler out (70 degrees).

Not quite half way thru the test, the truck stuttered, then belted out this HUGE plume of smoke from the tail pipe. The guy stopped the test because we thought a line or something had broke.

We checked things over, couldn't find anything obvious, so he tried again. This time, no huge smoke cloud.

The NOx were almost double the original reading, and the CO2 was a lot higher too (I don't have the paper in front of me).

Driving home, truck felt NO different, but, now it smokes (some) all the time, not just the little puff at start up.

Debating right now if I should 'dig in' or just cut my losses.

Frustrated right now......

Frustrated that I like this truck a LOT.

Frustrated that I even if I had the coin, I don't know a reputable shop to help me with this.

Frustrated I don't have time to jack with it myself.

Frustrated that another used vehicle is just gonna have a new set of problems.

Yeah, I know, cry me a river.....

$650 later, I'm legal again.

Took time off to work from work to work on the truck and it rained the entire time (no garage space).

I caved and had a Midas shop install a new cat and O2 sensor too.

Thanks for all the help guys, its appreciated.

Heads up: my next rant will be where exactly is the cut off for emissions testing.