Hi All-

Sorry for the incorrect title...it's NOx we're failing! We just bought a 1996 Discovery SE with 130K on it this past Monday. In Colorado, your car needs to pass emissions before it can get plates. So we've been doing the test and failing ONLY the NOx section.

*Failed NOx the first time after picking it up.

* Got some advice at Auto Zone...tried using a fuel cleaner to try and clean out the system, driving it around a bit to get that stuff in there. Failed

* Tried new set of plugs today in case it's not burning cleanly. Failed. Worse then ever actually.


So, there have been some modifications to this car that I wonder might be contributing...

* Someone removed the muffler(s), but not the catalytic converters. They wanted it to grumble...which it does. Iv'e read that the catalytic converters can do a lot of the work in cleaning up NOx. Forgive the dumb question, but do these wear out eventually, and would missing mufflers change the NOx output substantially?

* Someone recently changed out the air filter system to a 'Spectre' air filter system. Which I'm wondering if it's also changing the air flow in a bad way. Not sure what the point of that system is, but


Any ideas to try (obviously in order of least expense, we just bought a car 8-) ) would be GREATLY appreciated. Thanks for reading!

 

What grade of fuel are you running in it?
Are the cats original?
What's the revs at idle?
Have the O2 sensors been replaced.
Do you still have the original air box?
Where's the air temp sensor located?
When's the last time it passed smog testing?
Is the Check Engine Light on?
Have you run a scanner on it?
Are you sure the Check Engine bulb is working?

 

Thanks for replying! Here's what I know right now....


*** What grade of fuel are you running in it?
Premium (brought it home for 100 miles on midgrade, but I'm burning through it along with a fuel system cleaner)


*** Are the cats original?
Not sure...but they look like it...the metal is stamped with the LR logo. The original owner had it for maybe 18 years (said it was serviced by LR), then sold it to the person we bought it from who only had it a little over a year. He was trying to commute with it, but oddly enough wasn't enjoying the gas mileage.


*** What's the revs at idle?
About 800 RPM I'd say.


*** Have the O2 sensors been replaced.
Same as #2...just don't know enough history. So hard to say with stuff under there...it gets so dirty so fast.


*** Do you still have the original air box?
No, I asked the owner if he had ANY more parts just for a situation like this, he said no. It bummed me out because this is exactly what I was thinking I might need it for.


*** Where's the air temp sensor located?
Not sure...I'll try and locate.


*** When's the last time it passed smog testing?
Same as #2...I don't really know. Apparently they don't do this test in Wyoming. I asked for the history at the testing facility, but they couldn't give it to me. Dang


*** Is the Check Engine Light on? Have you run a scanner on it?
Nope...and it doesn't throw any OBD codes either. Things seem ok


*** Are you sure the Check Engine bulb is working?
Yikes, no...I had not thought about that. I need to check that. We drove it 100 miles home from Wyoming and it seemed to do fine. Seems to be running pretty well.


Also...shout out to Traverse City! The SO is from Wolverine up there, and I'm from Ann Arbor.

 

Shout out to a fellow Michigander! I was born in Colorado (Aurora) and grew up in Michigan since 5 (Grand Rapids). But now I live in Texas.... :/

If you can, include a picture of the intake setup so those of us here can verify it's all done correctly.
If that checks out, I would plan on replacing O2 sensors and if that doesn't get it, then new cats. Both items do go bad...

 

Yes, I agree the upper O2's should get replaced, the cats I'd say probably not until there's more evidence that points to them directly. Cat's are the last item on the list and they're not cheap.

In my experiences working on Rovers for a hobby (paid hobby) is that the piston tops collect allot of carbon, some of the thickest I've ever seen on any motor. They're notorious for it. I would venture a well educated guess that that is your reason for the high NOX readings. The only way to remove it honestly is to remove the heads. My pistons had acquired so much of it it created hot spots. Carbon the color of cement and ten times denser will hold heat long after the exhaust stroke causing pre-detonation (pinging) even while running 93 octane. I had to do allot of work to remove it from all eight pistons.

What I would do (cuz it's cheap an easy) is try an induction cleaning with Seafoam through the brake booster vacuum line. Keep the motor running during this cuz it will try to quit. You'll absolutely have to change plugs afterwards because of the carbon splash. It may take two or three times to get the most our of this kind of cleaning.

The Victors! is ringing in my ears......... Maize and Blue run in my veins.

 

Thanks for the insights you guys!

I've seen this Seafoam apocalypse on YouTube. Like this...


I'm game if you think it might help. Can you point me in the right direction as to where to dump in the Seafoam? (See attached) Do you just add it bit by bit and work your way through the can?

I took those shots of the engine today while yanking out the coolant overflow reservoir. It was leaking at the emissions testing place the other day, so they wouldn't test us. I took it off and cleaned the seams and put JB Weld all around there to try and seal it up. There seems to be a bit of pressure in there...is that normal? When I remove the cap, you can definitely feel it.

Anyway, if the Seafoam cleaning doesn't do the trick, we'll invest in the O2 sensors and try again. This testing is just killing us. I just wanna drive!

Thanks again, REALLY appreciate the insights.

 

You let the engine vacuum suck the Seafoam from the can, brake booster vacuum line. Direct shot into the intake and gets where it needs to go in large quantity. Do not jam the vacuum hose in the can, it'll kill the engine like now. Do it slowly, like feeding a baby formula, little at a time. The exhaust is going to turn pure white as your doing so, just let it roll. The original expansion tanks split at the seam, common issue. I suggest buying an aftermarket cuz they're better.

 

Ok...sounds like a plan. Thanks again for the advice.

Here's the line where I'm assuming the I'll be feeding the baby....



Thanks for the advice on the expansion tank. Will do.

It's really funny how predictable the failures are with Rovers isn't it? I haven't had one for ten years, but this new one we just got brings back memory after memory of the issues I had. The passenger seat switch isn't working...just like my old one. The window gets stuck down when you roll it way down...just like my old one. funny.

 

Squirt WD40 in the seat switch, it doesn't get used as often as the drivers does. The drivers window sticks for the opposite reason, it gets use more often and you either have a missing tooth on the window scissor mech or it's well worn. Yep on the baby feeding line.... exactly.

 

Perfect...Thanks again!

Next stop...Project-Smoke out the neighbors!