Lowering Emissions: 2 cats? Air injection? EGR?

[TGP37]

From what I heard, o2's fail towards the rich side. But nothing is absolute.

I bet you have a vac leak in a place that effects 1 cyl versus all 6. Like a bad o-ring to seal the injector on the LIM. Allowing unmetered air to lean out the specific cylinder. Seeming it barely passed, it would make sense if 1 cyl was dumping far too much NOX.

Did you examine the spark plugs recently for a lean burning cylinder?

Adding another catalytic would help a lot but it only masks the problem. And the problem is likely to snow-ball over time and become far more costly repair.

[jmgtp]

From what I heard, o2's fail towards the rich side. But nothing is absolute.

I bet you have a vac leak in a place that effects 1 cyl versus all 6. Like a bad o-ring to seal the injector on the LIM. Allowing unmetered air to lean out the specific cylinder. Seeming it barely passed, it would make sense if 1 cyl was dumping far too much NOX.

Did you examine the spark plugs recently for a lean burning cylinder?

Adding another catalytic would help a lot but it only masks the problem. And the problem is likely to snow-ball over time and become far more costly repair.

Last time I pulled the plugs they all looked the same and looked normal, but its been a while. I know at some point a long time back I had pulled the plenum off and when I reinstalled it I used the same gaskets so it's possible that it isn't sealing perfectly. It doesn't physically show signs of a leak (like a racing idle when cold, or stumbling, etc). I knew I should have replaced the plenum gaskets but at the time $30 was the cheapest set I could find. I just now found a set for $7 (Autozone) that only includes the plenum gaskets (all I need). I will pick them up and replace.

I got the cylinder for the Mig filled. Now its a matter of finishing up the welding which shouldn't take long at all. My chronic low back issue has been flaring up a bit more than usual the past 10 days so that's just one more delay I'm dealing with right now. I'm considering finishing it up tomorrow night but at the same time I can't risk further injury so it'll depend on how I feel tomorrow.

[robertisaar]

any kind of significant vacuum leak should show up as noticably less vacuum than normal, along with a really low IAC count.

[TGP37]

Maybe a dirty fuel injector? That could cause a lean condition and get temps to rise in that cylinder. In fact, you mentioned the car sitting for some period of time. I bet the injectors may have varnished fuel on the tips. Put some top-end cleaner in the fuel or do the DIY injector cleaning. Pretty cheap if you do it right. A can of carb cleaner, momentary switch, some fuel hose and a baby medicine syringe...plus car battery to cycle the injector. The can pressurizes the cleaner and injects through the injector. I did it once, really neat.

I've read NOx is formed with excessive temps. Somewhere along the way, the combustion temps are too high. Maybe timing is advanced too much or the engine is having a hard time cooling the combustion chambers. Maybe carbon build up is increaing compression ratio? (thats a long shot guess)




edit: After thinking on it, a partially clogged injector makes sense. They can "piss" fuel so the cylinder gets the fuel it needs but it burns terribly in liquid form versus a proper vapor.

[jmgtp]

The second cat is officially done. Welded back up and reinstalled in the car. I started it up just to make sure there were no leaks, ran for 10 seconds and all is well.
It definitely smells rich on a cold start but the rich odor is gone once it is up to temp.

To the above post, I've had a can of Seafoam destined for the gas tank of the Grand Prix. The reason I didn't add it is because the car was still in the process of being tuned and I wasn't sure if the Seafoam in the gas would skew anything tune wise.

[robertisaar]

seafoam is comprised of isopropyl alcohol, diesel and naptha... in small amounts, it wouldn't skew much, but small amounts generally don't get the job done.

[TGP37]

I had poured seafoam directly into the fuel lines/rail before during assembly. It won't run properly at first but it does get a concentrated dose pushed through the injectors under pressure.

People keep saying their is better stuff.......but I keep forgeting.

I would consider some approach to cleaning the injectors....as the car has sat for a time. If you worry about tuning results, having a pissing injector will definately skew the process. Even if not that, the presence of Nox indicates a combustion event that is far too hot. As I think NOX is created in excess of 2300*F.

And if you had to clean the injectors professionally, have them flow tested. That will do GREAT for tuning purposes.



That is, of course, if the injector is the problem. If the problem doesn't go away, try hanging the fuel rail intact above the LIM and have a friend turn the key to ON. The prime spray should be enough to see the problem if one exists. Just don't wave a flame at the mist....lol

[jmgtp]

Ok - good ideas.

I'm planning on replacing the plenum gaskets in the near future so its not much additional work to pull the fuel rail off. I can have someone key on to prime the fuel pump while I observe the injectors to make sure none are leaking.

Assuming none leak, at what concentration would Seafoam do any real work at cleaning the injectors? If I added it to a full tank? A half? Quarter? I'd then hold off on tuning until it I fill with a fresh tank to ensure that the different 'burning' characteristics of Seafoam wouldn't skew the numbers.

As far as home brew methods of cleaning, how would this fair:

Disconnect fuel lines from rail and remove rail from car, but leave injectors intact. Attach some fuel line to the rail and attach that to a sealed container of XXX brand injector cleaner. Use compressed air to pressurize container and a car battery to manually pulse 1 injector at a time (does holding an injector wide open without pusling damage? Or at least slow manual pulsing?). In theory I should be able to run fuel injector cleaner through the rail and each injector at a 100% concentration. Assuming I can fabricate something that won't leak under the pressure of compressed air (shouldn't be tough)...Will it work? I guess the next question is how many psi of would be needed?

[robertisaar]

no, holding an injector wide open won't damage it.

i've made a ghetto methanol injection setup using an injector before and never had problems. i just wouldn't do it for really long periods of time(30 seconds on, 30 seconds off should be sufficient).

and i would go with the kind of pressure you'll see in real driving, meaning a max of 43.5PSI(assuming you're using the older FPR, or i think 52PSI using the newer FPR.

[TGP37]

For seafoam, I would add half a can to a full tank of gas (12-15 gallons). Suck in 1/4 and drop 1/4 in the oil. Drive until the tank is almost empty, replace oil. I know the military has their own additive that is similar to prolong engine life. It is a great upper cylinder lube as ethanol is very dry and hard on walls. It also prevents varnishing injector tips.

I like to add a swig (3-5 cap fulls) per fill up. it does good for fuel system health.

Hey Robert, you mentioned a product once, better then seafoam? I forget the name, or if it was you that mentioned it.


The DIY injector cleaning is pretty effective. Most spray cans are around the pressure of 25-50 psi. So you do get a great blast cleaning. I stuck the little red straw into a baby medicine syringe. The injector fit into the other side real good. A cheap monentary switch and a battery. Took 1/2 hour to flush my injectors out. AND, you will be able to see the spray pattern easily and more safely. Especially if one injector was spraying different then the rest. Then I would pump cleaner until it sprayed right. or replace it.

Good luck.

[robertisaar]

i've never mentioned anything else, just how to make your own seafoam.

[TGP37]

i've never mentioned anything else, just how to make your own seafoam.

I wonder how much cheaper it is to make. Interesting idea there.