High NOx

[Rob]

Hello... Just s quick question. Recently had 88 Lincoln TC inspected and it failed for NOx. Im not a whiz with emmisions but I can work around them most times. Egr is woking fine but the themostat seems to be stuck closed. This will tell computer to run rich all the time...
Correct? This vehical has always passed with flying colors in the past.

Checked timing ok
Tuned up recently cap, rotor, plugs, wires air fuel pcv etc

Thanks

[DanD]

NOx is a product of heat and load, so you’re correct with the thinking that a stuck thermostat could cause NOx to increase and that the computer will make a small attempt (very small) by enriching the mixture to cool things down. But a rich mixture because of its cooling effect will lower NOx not create more.
Lean hot, rich cold.
It would be helpful to know what the actual NOx readings were along with the HC, CO and the cut points (limits) are.
You said the EGR is working, I assume as in opening, but when you open the EGR at idle does the RPM drop and cause a misfire if not a stall?
Another thing to look at is timing, a worn timing chain will cause valve timing and ignition timing to retard, you can (as most do) compensate for the late ignition timing by adjusting the distributor but all that does is add load. Because as far as the pistons are concerned there’s too much timing now, which will cause pinging, or detonation again adding heat, increasing NOx.
Carbon build up will change the compression ratio causing a ping; it may not even be an audible ping, again increasing heat.
We can’t forget about the good old catalytic converter, it maybe working fine for HC and CO but not doing anything towards lowering NOx.
Here are a few diagnostic charts that may help, some of the test procedures will require a gas analyzer but it’s the only way to know what the cat is actually doing.
I’m not saying these are the only things that will cause NOx to be high but these are the places I would start checking.
Dan.

[Catch 22]

Thanks DanD

I dont have a gas analyzer but I will check everything else that I can. Here are my readings...

HC grams per mile 00.48 Limit 02.00
CO grams per mile 001.51 Limit 030.00
Nox grams per mile 04.32 Limit 03.00
CO2 grams per mile 522.98 Limit N/A

I have some time this week ...Ill be tackleing this I hope.

[DanD]

It doesn’t look like the car is running to lean, but I’m not to familiar with grams per mile we here use PPM (parts per million) for HC and Nox and a percentage for CO.
With the Nox failing by as little as it did I’m thinking that the EGR and its passage ways are probably ok which may leave the converter at fault but that’s only a guess on my part. What I would try is decarbonizing the engine, I think you can buy kits that have some sort of metering valve system, that you can connect to the PCV circuit. So you can regulate the amount of a cleaning agent to be sucked into the intake and will clean some of the carbon out of the engine and possibly the converter.
I use this stuff from Bardhl and it seems to work well, I don’t know if you can get it where you live or not but something along this line could also work.
Here’s a link to give you an idea of what I mean.
Dan.
www.bardahl.ca/products/pmp/9300.html

[Catch22]

Thanks DanD

About two years ago I had to replace the right side converters on this car. Comes from Ford with 2 converters per side, but the aftermarket ones have 1 converter.Would this affect emissions? I would think the replacement would have to meets standards. Anyways I will look for a similar product....I live in the U.S. I'm sure something is available..I was thinking of puling off the plenum and cleaning it out real good myself.. Have already done the EGR....Nasty Thanks again Rob

[Tom Greenleaf]

I have a 1989 TC with just a converter on each side of its Y pipe same as my 88. Are you saying you had four??

I failed NOx on the 89 by .01 grams per mile and and on a legal sticker that forgives you for a year for being so close. I replaced everything for the retry and it was worse!! I'm ticked because I don't even think the machine is calibrated that close. It's ok for another year and I'll deal with it again then. I don't know if the car will last much longer than that yet it's still a safe car.

I have heard cleaning the plenum (upper intake manifold) can help. Good luck - T

[DanD]

A lot of the after-market converters are very appealing due to their lower costs and in a perfect world they will work fine.
I do a lot of converter testing here at the shop and the after-market converters are sucking a hind tit, like I said in perfect conditions they work fine but they are working at their max to control the emissions.
Even when input gases from the engine are at their best that they are designed to run at, I don’t think I’ve found any of these converters to be any more efficient then about 50 to 60 percent.
Yes there are likely standards for these converters before they can be sold to the public and that’s where I think they are using the system.
The chemists or whoever (?) that say a certain amount of the three precious metals Platinum, Rhodium and Palladium that make up the catalyst will reduce or convert the emissions for a said vehicle. The after-market people look at this and only give what is theoretically needed, the auto manufacturers know this is not a perfect world and to make sure the job gets done they add more then what the bean counters say.
Again because an after-market converter is working as hard as it can, it will burn out much sooner then an OEM.
So if you’re into keeping your car for the long haul you may as well put the OEM in and just suck it up. What’s more expensive a new converter every emission test or an original to last for years, that’s as long as an engine running condition doesn’t kill the converter?
An instructor told me this and I believe it to be 100% true, converters don’t die they are murdered.
Dan.

[Rob]

Thanks DanD

I think Ive got it licked. Egr was carboned up real bad. Pulled plenum and cleaned the carbon out of every nook and cranny, EGR ports and the intake itself. Wires,plugs,coil,cap and rotor all changed (It was about due). Got some Seafoam and treated the system. Took it out on the highway...OMG like a new car.
Timing was off so I checked the lash in the chain (just about 3 degrees) So Maybe its times for a set of gears and a chain. But it does have 135,000 miles on it ,so I cant complain.

Im gonna run the seafoam through a couple tanks of gas before I get it reinspected. Thanks again for all you help.. Rob

[Tom Greenleaf]

That product "Sea Foam" is awesome. Don't know what's in it but it works fast and better than anything I've used.

It's great for seasonal equipment if you didn't run them dry of gas. - T