My Dakota failed emissions....$650.00 later, I'm legal again

(Posting here since this section gets more traffic than the truck section)

Took my Dakota in for its annual smog test, and it failed the Low Speed NOx.

Am I wrong to think that if it was the catalytic convertor more readings would be out of spec?

I'm leaning towards the EGR, but that's just a guess. When I had the intake off (last year), I cleaned the EGR and the port out as much as possible, but, did not test or replace the EGR.

Plugs, cap, coil were all replaced spring of 2015.

Truck other wise runs fine.

Here's the link to the test results: Results



Oh, this is my '93 Dakota with 3.9 and 168K miles...

Suggestions?

Thanks.

Sorry to hear, when we used to have those tests here we would have folks come in with there mini vans etc to work and fill up there cars with our Sunoco 110 octane LEADED racing gas and then pass the test! I am talking about 10 years ago since we had the test here.

I know I took my 340 challenger through one time with a huge racing cam on straight 110 leaded race gas and it passed the first time.

Was your car really hot and blown out on the highway right before the test? They used to say that would help in some cases.

I spent the morning running errands, ran it around town, 20 miles down the freeway and back, and then when I got to the station, they took the truck right in, so there was no cool off period.

And, it was about 80 degrees out when I took it in.....

Got to clean it up at low speed it looks like? Got a fresh air filter in there? Good gas does make a engine run better and cleaner...

Have you noticed any pinging? My dad has a 1994 Dakota with a 3.9 and 180,000 miles. It pinged really bad under part-throttle acceleration and pulling hills. The water pump went bad, so I decided to replace the timing chain at the same time due to the mileage. The chain was stretched, not excessively, but enough to just rub the tip of the drip tab. Just finished last weekend and it runs so much smoother and quieter. The pinging was nearly eliminated. The engine has quite a bit of blowby, so I plan to install some sort of PCV catch can to eliminate the pinging completely. BTW - I did pull the intake a few years ago and installed the Hughes Engines' Intake Plenum Repair Kit to seal up the bottom of the intake. If you do replace the timing chain, be sure to install a tensioner to eliminate the knock and clatter that is characteristic of the timing chain in the 3.9 engine.

check the egr

My wife's '93 Ramcharger had problems just like yours nearly every year. Every time it was the cheap muffler shop cat was shot. The last one we had installed was at a real shop with the correct Walker cat con. It was about twice the size of the cheapy univeral muffler shop junk. Once, several years ago, we thought it was the EGR, replaced it, we were wrong, only last year did it really need replaced.

Robert

If there was no cat, the answer would be to lean out the idle and idle. A little readjustment of the idle mixture screws and maybe the throttle opening (idle speed). But the cat is also a possibility and to a lesser degree the EGR.

IIRC, the early catalytic converters were mainly to reduce the NOx. The other emmissions were controlled by running higher idle temperature (leaner, combined with an idle stop solenoid so it won't diesel on shut down). Your '93 probably came with a 3-way cat which was designed to help reduce all the bad stuff, but again IIRC NOx reduction is the main job of the cat.


So, if you fiddle with the idle-off idle, bring them to the specs on the hood sticker (if that's option on a '93) that could squeak it by.

The EGR valve operation should be testable with a vacuum gage and pump. If the EGR exhaust gas passages are partly plugged up - that's harder to do anything about. You can access the valve orifice but thats about it without a teardown. EGR systems usually have temperature and vacuum switches Off the top of my head there is no EGR until coolant reaches a certain temperatures, no EGR at WOT, etc.


If you want to read more about diagnosing exhaust for relatively modern cars there was a Toyota (ASE?) pdf online in various locations. This may be it here:
http://www.readbag.com/autoshop101-forms-h56

The catalytic convertor that's on there is of unknown origin and age.

When I bought the truck, the exhaust consisted of the original cat, a newer cat back where the muffler should have been, then a stupid little 'race' muffler not 6 inches off the back of the second cat.

When I had a new muffler installed, they took the second cat and replaced the stock one with it (the truck only has one cat now in the stock location).

There was a VERY noticeable difference in how the truck ran after doing this.

As for pinging, it hasn't pinged at all since I did the plenum and intake gasket (and when it did, it was only slight).

I'm going to get after it in a few minutes......

Well, got the EGR off. Still just as clear as when I cleaned it.

Not sure how the electrical connection plays into it, but, lacking a vacuum pump, I gave it a suck with my mouth.

No resistance.

Being no resistance, I carefully blew into it, and felt air coming out from the diaphragm.

That's not good, is it?

Had a '90 Dakota w/ 3.9 w/120,000 miles that failed inspection. Took EGR off, cleaned it, truck passed. The following year, truck failed b/c of EGR. Took it off, cleaned it; truck still failed. Replaced EGR and truck passed. Sometimes the cleaning helps, but only to a certain extent.

Replaced the EGR this morning. It made a noticeable difference with how the truck runs and sounds.

Drove all over this morning running errands, took it even further on the freeway, then took it back for another test.

Too soon?

It failed NOx by a much larger number this time.

Grrrr......

A scan tool would be helpful to look at engine data. Ensure the engine is in closed loop fuel control,O2 sensor is functioning properly,fuel trim data is in range,coolant temp is correct,etc. NOx is created by combustion chamber heat.....anything that could cause combustion chamber temps to go up will increase NOx production. EGR is designed to reduce those temps...just because it's new doesn't mean it's working correctly. Lastly the reduction portion of the 3-way cat is designed to reduce NOx at the tailpipe.

its probably the cat.
i went thru the same exact thing with my old truck...

The Lambda shows in the lean, but acceptable range. The aftermarket Cats are marginal on a good day and garbage otherwise. Before doing that I'd throw an O2 sensor in there, disconnect the battery for awhile to clear the adaptives and give it a shot. In '95 O2 diagnostics were lousy, the sensor can be pretty far off and not throw a code. It should only run $50 or so to replace- I'd recommend the 1) O.E. or 2) NTK sensor, I've had mixed results with the Bosch sensors. O2 switching is very important to keep the A/F in the range(s) that allow the Oxidizing AND Reducing beds to work properly. HTH, Steve

I'm not 100% at this point, but, I think the original O2 sensor is still in there. I ran out of daylight before I could find the plug end.

I'm disappointed about the results of the EGR even more so because of how much better the truck is running. Even the inspection guy made a comment of how it sounded different when I pulled up to his shop.

Are Bosch sensors that bad? It's all I have readily available without ordering.

I can't do anymore until Saturday.

Thanks for the replies!

Oh, and about that scan tool.....I checked with a couple of shops, none had the ability to scan an OBDI system.

Maybe if it were a Chevy or Ford.......

If it's just a matter of a day or 2 I'd order one. I got rid of all my personal OBD1 stuff years ago, no $$ in it, even where I work we have just about gotten rid of all those- I work for a school district,and the 20+ year old stuff is HD or diesel, so no diagnostics. Finding guys that are proficient in those old systems is getting tough, we are all retiring or getting out of it, I've got another decade min, if my body can hold up.

Is this the same Dakota that suddenly started sucking down oil, then fixed itself?

You have lots of room on your HC. If you put in some 94 Premium or whatever you have available, it will lower NoX but it will raise HC.

Make sure your cooling system is doing its job ie running the lower side of normal not the higher side. NoX is caused by high combustion temps so everything you can do to control temp helps. That's why Premium fuel will reduce NoX because it burns slower/cooler. It will raise HC for the same reason.

I used to have a 3.0 V6 Spirit that failed the same way. Lots of room on HC but failed NoX similar to yours.

Went to town and filled it with premium and it passed NoX by about the same margin it failed by and BARELY passed HC.

Kevin

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.

DANG that's high!

In Texas it's 25 years to emission checking freedom. 2017 may be the last time to have to pass? It wouldn't surprise me much if they extended the limit.

Robert

The $650.00 was the total of everything, not JUST Midas.

Taken directly from the TX.gov website:

Quick Facts:

Houston-Galveston-Brazoria Program Area: Brazoria, Fort Bend, Galveston, Harris, and Montgomery Counties
Dallas-Fort Worth Program Area: Collin, Dallas, Denton, Ellis, Johnson, Kaufman, Parker, Rockwall, and Tarrant Counties
Austin Area: Travis and Williamson Counties
El Paso Area: El Paso County
Motorists must successfully pass both the emissions and safety portions of the inspection prior to receiving a vehicle inspection report, which will be used to obtain a vehicle registration sticker.
Gasoline vehicles model-year 2 through 24 years old are inspected annually beginning with the vehicle's second anniversary.
Remote sensing element randomly inspects vehicles emissions on highways.
All inspections are collected at a central database.
Recognized Emission Repair Facilities ensure quality repair of vehicles.
Waivers and time extensions are available for eligible vehicle owners.
To find the nearest certified inspection station, use the Texas Department of Public Safety(DPS) station locator Exit the TCEQ.
To locate a Recognized Emissions Repair Facility in your area, use the DPS repair facility locator

Talk to four different shops, you'll get four different answers. Same thing when asked at the DMV.

We had something like that in Colorado, but with a democrat Governor and both statehouses, the rule was changed to ONLY 1975 and older cars get "collector plates" which only require you pass the test once, without further annual testing. Cars with collector plates already were grandfathered. I had let the collector plates lapse on both my '76 and '77 and now I'm stressed out if I want to be strictly legal.

R.

Do you know what make and model number of new catalytic converter Midas put on?

Glad you passed.

I was told it was a universal magnaflow.

There's no part # on the receipt and I haven't climbed under the truck to look for a part number.

Thanks for sharing the Magnaflow info.

Earlier in this thread i browsed the Rockauto selection of 1993 cat cons and had the suspicion that some might be more effective than others, since the two brands that met the ridiculously tough California NOx specs were much more expensive.

I would guess that a "universial" cat con sold in 2016 might have much better NOx reduction than the original cat con from 1993

I would guess that a "universial" cat con sold in 2016 might have much better NOx reduction than the original cat con from 1993

I would think (hope) so too. The original cat went bye-bye right after I bought the truck. When I got this truck, it had two cats on it, the original one, then a second one back where the muffler usually goes. Then, not 6" off that cat they had a 'race' (?) muffler about the size of a shoebox, and dual tail pipes off that. The truck was loud and sounded like crap.

When I had a shop put a proper muffler and tailpipe on, they removed the original cat and installed the newer looking second cat up in place of the stock orignal. How old it was or what kind of shape it was in I have no idea. It just 'looked' better than the 22 yr old piece.

While the $650 tab still stings, the truck runs so, SO much better now, its like it lost 100K off the odometer. Hands down, the new EGR made the biggest difference, even more so than when I did the tune up.

If I had spent $650 only to have it continue to fail and /or run worse, this might've been the next step.........

The primary cost of a Cat is the Platinum and Palladium catalyst elements, the aftermarket Cats either A- cut corners and don't work well (or for very long), or B- cost nearly as much as the OE units. In CA the OBD2 Cats have to warranty performance= OE spec, so they cost much more. I.E. you get what you pay for. Cheap Cats will get you through this time, but in 2 years

Colorado also has roadside drive by emission checks. My Durango has not been to a dyno inspection in 10 years. BTW, the collector car plate program is due in large part to lobbying by the Collector Car Council of Colorado and I applaud their efforts to keep the system in place.
Craig