Failed emissions

[ScottD]

My 90 Dakota Sport passed emissions 2 years ago with 193k on it and the ORIGINAL cat.

Now, after putting on Edelbrock headers, a new EGR valve, new 02 sensor, a 180 degree t-stat, and a Catco cat, it has failed twice. The plugs, wires, cap and rotor all have under 10k on them.

Thoughts? Is the Catco cat to blame?

[88_pacifica]

Are the headers quite a bit bigger and the thermostat significantly cooler? That could add to a higher percentage of unburnt fuel into the exhaust....

[karlak]

thermostat

[JamesL]

Make sure the the car is hot when you bring it in. I'd go up on the thermostat especially for winter in MD.

[ScottD]

Stock thermostat is 195. I put the 180 in.

The headers are not huge by any means.

[88_pacifica]

Stock thermostat is 195. I put the 180 in.

The headers are not huge by any means.

Yep, sounds like the thermostat. I would also run the highest octane you can(even a little additive for emmissions)and be sure the IAC is good and clean. Also, be sure to make sure that the idle isn't too low as that can hurt emissions as well...

[ScottD]

It seems to idle fine, if the IAC is held in with loctite'd screws like on the TM's I'm not touching it! :-)

I did run 93 octane on this last test.

Thanks for all the feedback so far!

[contraption22]

Defintitely put in the hotter thermostat. If the puter reads anything like my '93 TBI, coolant temp has a significant effect on idle speed, fuel mixture, etc.

If you have the option, get a Stant SUPERstat or quivalent. Its a couple bucks more, but it maintains coolant temperature better than a standard stat. You'd think that they would just make all their stats as good as the Superstats, but no.

Also, did you get a printout that tells you why it failed? Often you can tell by the readout of the emissions machine what the problem may be.

[shelbydave]

Did you move the cat from the original position? If you moved it farther back on the exhaust, it may not be getting up to temp.

[turbovanman²]

Readings? You failed Nox, right? My guess,

I bet 100% the cat, Catco's are garbage, they are on the lower scale of crap, I bet they use the thinnest layer of coatings possible. 90's Dodges need a Walker Super cat, I have a number to use or OEM.

[Juggy]

is that a TBI dakota??

if so whered you get those headers??? i can only find 92+ magnum stuff!!!
any gains?? what else have you done to it? dont mean to hijack!!

but yeah I had a catco 2.5" cat on the 3.0 back in the day and it wouldnt pass E test...kept failing the last one, it was blowing the reading away like 2400-2500ppm

[ScottD]

First time just failed Nox. That was an 80 degree day.

Today failed Hydrocarbon and Nox. It was raining today though and Nox was down significantly though not enough to pass. Today's temp 43 degrees at time of test.

Cat is in the stock location. All EGR stuff is hooked up. I've heard of Catcos failing on other turbo Dodges.

Thanks Mike for the thermostat tip. They charge more because people are paying it. Stant must be a capitalist corporation and not non-profit, damn them :-)

Headers came from Summit. A little pricey but well worth. Mods are pretty basic, 180 t-stat, 2.5 cat going into 3 inch cat back, cold air induction, K&N drop, and the headers. Mods made a nice difference.

[89ShelbyGuy]

i know when my pops has an old carbed omni, it would'nt pass, so we took it to my cousin, he adjusted something on the carb,,the car ran like crap...took it there and passed with flying colors...then after it was done, he readjusted the carb in the parking lot and we drove off...

[contraption22]

Thanks Mike for the thermostat tip. They charge more because people are paying it. Stant must be a capitalist corporation and not non-profit, damn them :-)

Haha... what I meant was, when you have the capability of building a better product for a fair price, why would they want to put their good name on a lesser product?

Obviously it must be profitable for them or they wouldn't do it I guess....

but anyway... thats off topic.

[turbovanman²]

180 stat won't cause NOx, it will help so leave that alone. Put this cat in and it will fly thru-

You have a choice of good Walker Supercats, 2.5 inch #15146 or 3 inch #15147 and if you want to spend a little extra, this cat will pass anything, even Rotaries, 2.5 inch #15067 and 3 inch #15068.

[JDAWG]

Take tags off till 2010, its only a year away.

Scott I have take out AIS motors plenty of time with no problems

[ekimdam]

Thermostat then cat is the order I'd try.

As far as using the highest octane possible, I'd have to disagree. Use the lowest octane you can get (prolly 87) and get the thing as hot as you can without killing it.

Higher octane fuel, while good for anti-knock and making more power, doesn't do a good job of getting completely burned up in lower compression engines and has a greater probability of leaving the cylinder as unburned/partially burnt fuel. Also, you need a lot more heat/compression (energy) to burn higher octane fuel more completely or more time for it burn.


High octane = slow burning
Low octane = faster burning

[ScottD]

I can get historic tags for it this January. MD law says 20 "model" years. I just renewed the tags though, which is why I want to get it through.

The cat is welded in. I really don't want to go through taking that out.

Putting a stock 195 t-stat in isn't a big deal.

I'd read some articles on line suggesting using 93, which I did. Most of the time I run it on 87.

[black86glhs]

Have you checked the timing? To run 93 octane, you would need to bump the timing up slightly to take advantage of the octane. The other thing is the EGR system. It may be hooked up, but does it flow enough to actually work. Apply vacuum to the valve at idle and see if you can get the engine to stall. If it doesn't, you have a blockage of some sort somewhere in the EGR system.

[shadow88]

My vote will always go with the cheap aftermarket cat.