Do the Cats needs replaced ?

[m00npie]

96 Explorer 4.0 V6 Sport 4x4 (125,000 miles)

Check engine light is on and is caused by the rear catalytic converter according to the garage that I took the truck to.

So here's the question(s):
-Does the on-board computer have the ability to tell you which converter is bad?
-Once the computer is reset, it takes a while (usually a full throttle run on an incline) for the check engine light to come back on. So does this mean that the 'Cat' is starting to go bad and does not need replaced yet, or does it mean that it just takes a while to register and I should replace it right away?

Finally, if the back one or front one is bad, does anyone know of an economical replacement that does not sacrifice the 'back-pressure' issue with high flow cats?

Any meaningful response would be greatly appreciated.

Thanks.

 

[Maniak]

The ODB-II computer has o2 sensors before and after the cats... I know they can tell when a Cat is going bad, but I don't know if there is an o2 sensor in front of the first cat, and between the 2 cats and after both cats. If so, yes, it can tell which cat is bad. If it only has os sensors in front of both and behind both, it can't tell which one is bad.

Also, when you have ODB II you do need to get the more expensive emision cats. From hanging around an exhaust shop (while getting the cats replaced on the neon and replacing teh exhaust on the X) I learned that they can use the less expensive cats on eec-Iv systems but on odb-ii systems they have to use a more expensive cat, otherwise they set off the CEL

~Mark

 

[Alec]

You should do a flow test if you haven't already to determine if it's truly the cats or possibly the O2 sensor itself. Or just have another mechanic take the cat off and look at it.

If you still have the stock exhaust manifolds you shouldn't have a problem going to a single high flow cat.

BTW, Welcome!

 

[m00npie]

Thanks Mark & Alec for your time & info. I did have some follow-up questions based on your responses.

Mark - Do the "expensive emission cats" simply mean buying directly from Ford?

Alec - I have the original exhaust from the factory including the manifolds.
- Do you recommend a particular single high flow cat? (Brand, size, etc…)
- NY State requires emissions testing. In addition to passing the emissions test, do these emissions stations actually verify the amount of 'Cats' on the vehicle? In other words, do they know how many 'Cats' a vehicle comes with from the factory and verify the same # exists? Being from another state, you may not know this, but anyone from NY that could shed light on this would be very helpful.

 

[Alec]

By emissions laws you need to keep the stock cats on for 8 years unless they're bad. When you go for inspection, you should have papers showing your stock cats were bad. Besides that, as long as you pass the sniffer tests you'll be fine with one cat; I pass the tough pollution tests down here with one cat and the supercharger.

Any good exhaust shop should be able to get you and install a cat that will work.

 

[Maniak]

The "emision" cat isn't from ford, just cost $40 more.. something about how clean it makes the exhust.. if it doesn't make it how the computer thinks it needs it, a CEL is tripped.

We replaced both cats on our X with one generic high flow cat.. (2.5" in/out) and replaced everying cat-back with 2.5" pipe, and a Generic "shop brand" high flow muffler with 2.5" pipe out the back.. I'm very happy with how it sounds on our ohv motor.

I can't asnwer about NY, but in Arizona, you don't need to replace 2 cats in series with 2 cats in series, you can replace it with 1 cat, and we do have emision testing here.

~Mark

 

[xplordakota]

You should do a flow test if you haven't already to determine if it's truly the cats or possibly the O2 sensor itself.

how do u go about this??

 

[chadb]

Swap O2 sensors

You could swap O2 sensors and see if it's the sensor. I think they are the same model sensor? You might also see if someone on this board has an old one that probably works ok to let you swap it with to check it. I have a used one that seems ok from a 95 Explorer. Mine doesn't have the after CAT O2 sensor as far as I know.

 

[ExplorGM]

AZ Emissions- Maniak or Rick or...?

Mark or Rick, or...,

About to take the X in for Emissions testing. A couple of questions for AZ...

Do they care where the exaust exits? Mine comes out the side now.

On 95s do you know if they use the "sniffer"? On our 98 Sebring (I assume because of the OBDII) they just connected to the computer without sniffing.
On the X no codes are popping up, but it has been running rough. After cleaning the MAF and tightening the intake bolts it seems to be running better, but I am still worried... Still needs head work.
I've been working so much the truck has been severely neglected... Have some time off now, but registration due by the 15th...

Cats are still stock. What Alex mentioned about the 8 year rule... Does that apply to AZ? After testing is over I sure would like to clean up the rusty mess down there and go with only one Cat, but it will need to pass again in the future!

Do you recommend changing out the O2 sensors prior to the test? Anything else?
Thanks!

 

[Maniak]

I don't live in phx anymore.. and since that is Maricopoa County, Phx, metro, they have harder/more stringent tests than they do down here in Tucson..

From what I remember/see on their website (http://www.adeq.state.az.us/environ/air/vei/overview.html)

I'm not sure about the '95.. BUT If Your '95 has ODB II it MIGHT just have the on-board-diagnostics done.. I know our '95 dodge neon has odb-II and they do that test here in tucson instead of the rollers on our '95 with ODB II.

But More likely, your going to get the IM 147 test.. which is the sniffer test on a dyno at varying speeds.

I know in tucson, your exhaust can go out the side BUT it must be past the rear doors AND must reach the side of the vehicle. A friend down here in Tucson had to put on an exhaust extender (just a pipe with a clamp) to extend his exhaust 3" so they would test it.

Oh.. this link will come in handy... its the wait times for the emisions testing facilities...
http://www.gordon-darby.com/cgi-local/waitupdat.pl

Good luck.....

~Mark

 

[ExplorGM]

Thanks Mark

Thanks Mark!

From the web site, it looks like they'll put it through the full test.

This might be a dumb question, but if the mixture is running rich, wouldn't the "check engine" light come on with a resulting error code?

 

[ExplorGM]

Old results comparing AZ and CT...

Interestingly the truck passed in 10/27/2001 with these results:
HC-.10 Max limit 1.60
CO-3.78 Max limit 20.00
NOX-.97 Max limit 3.00
AZ tests in Grams/Mile

When it was done in CT on 4/10/01 these were the results:
HC-2.7ppm Max limit 151.0
CO-.10% Max limit 1.68%
NO-10.00ppm Max 956.0ppm

Since those were done, it has had new injectors, EGR, O2 Sensors,fuel filter, and all the usual tune up parts. Thinking it might be time to test the FPR?

Considering the differences in measurements used in the two states, can anyone tell me if the AZ reading was better or worse than the CT reading??

 

[ExplorGM]

Passed!

Well it passed. It still has a misfire at idle, but the test they ran was a 28 second test at high RPMs.

I did have to take it back a second time to have them test it as they would not test it even with the exaust extension that I had put on it. Said it was still too close to the tire so I put on the goofiest looking extension coming out under the frame but over the spring and then going forward towards the front along the frame with a downpipe... Just enough to take it forward away from the tire. When the guy looked at it he was some bizarre factory exhaust!

Passed with slightly higher readings than the last time in 2001. For others info, the truck has 149K miles on it with these readings:
HC (grams per mile) .40 vs 1.6 max standard
CO (grams per mile) 6.34 vs 20.00 max
NOX (grams per mile) .93 vs 3.00 max.

VS 2001 the NOX was lower, the HC was 4X and the CO was a little less than double.

 

[lonestar]

I had my exhaust replaced from the cat back and he mentioned my cats may be bad, or clogged. They said the muffler was full of stuff and it looked like the cats may be getting hot. The guy told me to drop by sometime and he would measue the pipe temps to see if there was a hot spot in the cats and to listen for a ticking sound or rotten smell. I was told there should be no more than a 100 degree temp diff from one side of cat to other, and a clogged cat would show a spike.

Does any of this sound right?

I was also told that explorers don't really like aftermarket cats. He tried to replace them with a high flow before and it caused the engine to miss due to loss of backpressure and only recommended replacing them with oem. How much does that cost?

He seemed pretty legit compared to some other places I called.

 

[Alec]

He sounds mostly right, though a Carsound cat will be just fine. I wouldn't waste the money going OE (probably costs 2-3 times as much).