I've read through a lot of the information on the site first of all. Just hoping for an extra set of eyes.

My failed emissions reading.

DRIVING TEST
HC, Max 143, Me 49, Average 19, PASS
CO, Max 0.71, Me 0.36, Average 0.07, PASS
NOx, Max 1145, Me 1896, Average 173.5, FAIL!

IDLE TEST
HC, Max 217, Me 16, Average 13, PASS
CO, Max 1.66, Me 0.02, Average 0.01, PASS

So my vehicle is doing better then years past in all areas except for NOx.
This test was done with my timing retarded as I barely passed on NOx last year. (I don't recall what I retarded it to though... maybe 0)

New plugs, new o2 sensor, cat less then a year old.

My engine is really carbon fouled. I'm going to run a few cans seaform type stuff through try a good cleaning.

Engine burns oil, about a 1litre every week or two. Engine has been run really rich most of it's life also. Lot's of carbon buildup. I'm finially ready to start my engine rebuild in feb or march hopefully, but I need to pass aircare in the next month first.

My EGR seems to work properly. Vacuum is applied to egr at higher revs, if you apply vacuum to the EGR manually or push on the diaphram while idling, car bogs down and wants to stall, like the tests describe.

If my EGR seems to be working like described, is it still worth it for me to remove it and try cleaning it? Maybe the passageways are working, but everything is restricted?

So I'm not sure what else to do. Before testing next I'll do an oil change, inflate tires to max, put some emissions past stuff in the tank.

Not sure about timing. Could it be retarded too much? I've been playing around and truck actually seems to run better slightly retarded

Thanks for the read!

 

You might want to look up how to check the secondary air(pair?) its the tube that runs from the airfilter box up the airtube, underneath the intake, around the back of the engine to the exhaust manifold. I thought that I read that helps reduce oxides of nitrogen NOX but not positive

 

The PAIR injects air into the exhaust to help the converter reduce hydrocarbons, carbon monoxide and oxides of nitrogen into carbon dioxide, water and molecular nitrogen. If the PAIR system wasn't working I'd expect to see high hydrocarbons as well.
There's a chance the converter needs replaced since it does affect NOx emissions.
However, the primary cause of high NOx is high combustion temperatures (which is why retarding the timing can affect it). So if you have a large amount of deposits in the engine that could cause high NOx as well.

 

I got my cat from maremont for 60 bucks, passed smog with flying colors with it.... do a google run on em to find the right part for ya.

 

If you have carbon buildup (and oil loss) as you describe, you might want to check the passage from the egr valve into the plenum. I have a V6 (and don't know much about the 4), but on my V6 the egr tube that extends into the plenum was completely surrounded with "gunk." (I think that's the correct word.) At some point, that would sufficiently restrict the flow that the EGR valve wouldn't be able to put enough exhaust gas into the air stream to work.

Cleaning was non-trivial; cleaning the tube (once out of the plenum) is easy, but cleaning the inside of the plenum is not due to difficult access.

[Though your test, with the engine bogging when you manually work the EGR valve, contraindicates all of this.]

 

Steam-cleaning the cylinders wouldn't turn. Take your truck for a hard drive and spray some water through the brake booster like you would do with Seafoam.

 

yeah, if there is a lot of carbon build-up in the cylinder, it will raises combustion temps and increase NOx. Seafoam is good, a small amount of water dribbled into the engine is also good for steam cleaning the engine out - jsut make sure water doesn't pool in the intake and you don't pour too fast (maybe tilt truck over so the intake is all "downhill")

 

x2 on the EGR is fouled/not up to snuff anymore.

 

sounds like it's working properly to me, and the fact that it bogs down and wants to stall when you actuate it means the passages should be clear enough to pass exhaust . . . though just for s and giggles it wouldn't hurt to take it off and use a pipe brush / carb cleaner on the passage.

 

well for the nay-sayers...this was a Cali emissions test done on Sin91's truck on Tuesday (see the date at the top):



Notice that it passed hydrocarbons and carbon monoxide tests....

Can you guess what the cause was?



So I can say with some experience that a converter can cause high NOx.

 

oh yeah, by all means. The converter material can even be there and still not do it's job, it can get contaminated by antifreeze or silicone which will prevent the chemical reaction from happening. Old age on the converter will also cause ineffective catalytic action.

 

Well, I cleaned out the egr, it wasn't in too bad of shape. The passageways into the plenum were fairly clean also as far in as I could tell. Carbon coated, but not blocking.

I ran a couple cans of seafoam. One through the tank, one through the intake w/ a bit of both in the crankcase.

I also put a bottle of emissions "KLEEN" guarentee pass into the gass tank and it didn't seem to make a difference.

I failed aircare again today w/ high NOx. Actually about 100ppm worse then last time...
I was 1984ppm. allowed is 1145. This was with the timing set to 0deg w/ the connector shorted.

I have another theory though. My 4th cylinder spark plug is cross threaded so it doesn't go as deep into the cylinder. I tried using a tap, but didn't want to go too hard.
When I pull the plugs, this 4th plug always looks mostly clean, while the rest are quite dirty. When I look at the header tube coming from this cylinder, it has evidence of it being much hotter then the rest of the tubes. Colour dirtortion. hot enough to burn crap off of it.

Is there a longer spark plug that I can try using in that cylinder that might help it burn better?

I think I've decided to buy a remanufactured engine. It would be nice if I didn't have to do it all under an air-care impossed rush.

The convertor is welded on and is less then a year old. I think I'm going to replace my whole exhaust anyways again in a few months (too loud, probably taken some life out teh convertor w/ poor running engine). But I'd rather not have to pull everything right now as there's no time

cheers.

 

Your EGR is functioning when you manually move it, but is it getting the proper vacuum under driving conditions? The two major controllers for NOx are the EGR and the Cat. If your cat is less than a year old, it should still be functioning. I'm thinking the VSV that supplies the vacuum to your EGR is stuck closed.

I would add a Tee into the vacuum line to the EGR, hook my vacuum gauge to it, and go for a drive @ 25mph. Make sure the EGR is actually getting vacuum. If not, you must fix it before going any further.

 

Not having the spark plug electrodes inside of the combustion chamber should cause an elevated HC emission, which you are not experiencing.

Checked the converter yet?

Unfortunately, your tests don't show NOx at idle so that makes it very hard to figure out what the problem is.

 

I keep failing due to high NOx. Before the first test I changed the oil and topped off with fresh gas on a truck that I don't drive very much. Test results:

10/26/11 15mph 25mph
%CO2 13.9 13.5
%O2 1.6 2.3
ppm HC 150 28
%CO 0.25 0.01
ppm NO 1502 1233

I installed a new O2 sensor and installed new plugs. Confirmed that EGR was functioning properly. Test results:

10/27/11
%CO2 12.1 11.4
%O2 4.0 5.0
ppm HC 82 31
%CO 0.00 0.00
ppm NO 2403 2098

I adjusted the valve clearances and replaced cap and rotor. None of the valves were off by more than 0.001" and the cap and rotor had fewer than 5K miles on them. Test results:


11/11/11
%CO2 13.7 14.0
%O2 0.2 1.3
ppm HC 247 55
%CO 1.80 0.01
ppm NO 1359 1382

Installed a new MAGNAFLOW direct-fit catalytic convertor. Test results:

1/11/12
%CO2 12.6 11.0
%O2 3.4 5.6
ppm HC 19 15
%CO 0.00 0.00
ppm NO 1951 1757

Replaced functioning EGR valve and vacuum modulator. Test results:

1/12/12
%CO2 14.0 12.4
%O2 1.6 3.5
ppm HC 14 12
%CO 0.01 0.00
ppm NO 1496 1322

During a subsequent "free" test at my local smog shop, the technician temporarily disabled the EGR during the 25mph test. The NOx jumped from about 1500ppm to about 3200ppm. The EGR seems to be doing its part.

Is it possible that the MAGNAFLOW cat is defective?

Any other suggestions will be appreciated.