Yes. If the leak if upstream from the O2 sensor, the readings can be skewed by the extra air coming in.


Very much so. The redux bed of the catalyst depends on a rich mixture in order to reduce the NOx coming through. If you have an exhaust leak, the O2 levels remain too high for the catalyst to burn off the oxygen it has absorbed, thus no Nox reduction.

I failed the smog again today after a major tune up. I replaced the leaking gasket, and even put 2 gallons of secret sauce in the tank. It wasn't running smooth, so I filled it up with 91 gas since I missed the test yesterday. So I arrive with a full tank of 91 with 2 gallons of sauce in it, and what happens? The first thing he says is that he can fix it if it doesn't pass, which gave me the feeling that he manipulated the test. Anyways, my results were the same, almost identical numbers on the NO part, gross polluter as a result. Also the retard who did my timing set it to 17 (!!!) instead of 7. I need some serious help here. How do I set the timing back to normal? And more important, since I am about to put a new engine in (another 2,6), does that contain the possible parts that might have caused my high NO level? Don't want to start replacing things if they sit on the engine anyways, since it is getting thrown out..
Thanks.

For high NOX I suggest you look at your timing, EGR valve, catalytic convertor, and fuel mixture.

Your timing is way off for your altitude. As mentioned before, it should be 7-degrees BTDC +/- 2-degrees with idle set to 800 +/- 100 RPM (see note below). Use SAS-1 to adjust your idle.



Regardless of what the mechanic said about adjusting it possibly making it worse, if you can't get it to run right with the timing set where it should be then something else is wrong and not setting it correctly won't help in finding the problem. Of course, if you can't set it correctly then something else is definitely wrong.

The EGR valve can often get gummed-up with carbon. Cleaning your EGR valve is easy to do.

Your rough idle when cold is probably due to your choke not set correctly. Just make sure when you go take your emissions test again that the engine is plenty well warmed up. Take it for a good half-hour drive right before you go test it.

If your cat is the original one, it may be time to change it. If the head gasket has blown in the past (somewhat likely on a 2.6) then the cat may be getting plugged up, preventing it from scrubbing the exhaust properly.

If your fuel mixture is too lean your combustion will be too hot and may produce NOX. Fuel mixture is adjusted with the MAS adjuster (see image above). Clockwise = leaner, counterclockwise = richer.

*** NOTE: There are several adjuster screws on the carb and adjusting the wrong one can be bad as it is set at the factory and shouldn't be touched. If somebody in the past has monkeyed with SAS-2 it can be troublesome to get it set back right. In short, be careful which one you adjust. Don't mess with SAS-2. ***

The guy who set the timing adjusted somethink around the distributor, he turned the whole thing so to say. but how do you get it just right at 7? Where can I find the EGR valve?

EDIT: Also, how much should I turn them revolution wise? And when do I know if the MAS is set just right?

When you adjust timing you slightly loosen the distributer bolts...enough to be able to barely turn it. With a timing light hooked up to the battery terminals, the pickup clamped around the #1 plug wire, and the light pointed at the pulley on the front of the crank, you'll see the timing mark lit up each time #1 fires. This mark will show next to a fixed measure (like a mini-ruler) on the front of the engine (I can't remember how it looks on the Montero, but you'll probably see a "0" with several tick-marks and a "10"). Tapping the distributer by slight bits rotationally in one direction or the other will bring timing forward or backward. Get it set to 7 +/- 2.....check idle.....get it set to 800 +/- 100.....check timing again (adjust as necessary).....check idle again.....you get the idea.

IIRC, the EGR valve is right below the carb. It's easy to get to. It's held on by two bolts and two hoses. When you take it off you might get away with reusing the gasket, but I'd suggest getting a new gasket (couple of bucks). Clean out the carbon any way you can but be careful not to damage the bellows. Carb cleaner helps nicely but try to avoid getting it on the bellows.

For MAS just use slight adjustments (1/8 to 1/4 turns) counter-clockwise. It'll be hard to tell what'll be right without an exhaust gas analyzer, but you can try adjusting it a little bit at a time and see if it has a positive effect on performance. You might try checking out those other items I mentioned first, though, before adjusting the MAS. If you do, however, be sure to write down how much you're turning it in case you need to set it back where it was.

For adjusting the idle speed, it'd be best to have a digital meter available.....one which can read RPM. It's connected to the coil and ground and will read much more accurately than the dash RPM guage. Turn SAS-1 as needed to dial RPM in toward 800 RPM.

Edit: By the way, when you're setting your timing and idle speed, make sure all your electrical accessories (lights, radio, fan, etc) are turned off. If you have something on, drawing power and making the alternator working, your may not get things set correctly. Also, point your front wheels straight so that your power steering isn't actuating.

You will get the best hellp here if you post all of your emission numbers. Idle, 15mph and 25mph. Do you have all of the data?

Here is a good link for troubleshooting.

Smog Test Troubleshooting.

Couple pointers...on the 2.6 the distributor only has one bolt. Loosen it, and you can turn the distributor to set your base ignition timing.

Idle speed is adjusted with SAS-1 as indicated, however, if you have any doubt as to where SAS-2 is you can read my post from a day or so ago about setting up the dashpot. Part of the procedure for getting that adjusted involves manipulating SAS-2. It's not a real big deal, by now there isn't going to be a single mikuni that hasn't been 'tweaked' by an inexperienced mechanic. I've yet to find a tech who knows how to do it right. I figured it out mostly by trial and error. It's not a cardinal sin to adjust SAS-2, regardless of what the Haynes manual says <img src="/forums/images/graemlins/wink.gif" alt="" />

The easiest way to fix NOX emission issues is to ensure your EGR valve is working. If you pull the vacuum line off of the EGR valve, you should be able to hook up a handheld vacuum pump to the valve and with even a slight amount of vacuum stall the engine. If you don't see a massive deterioration in idle quality and/or an engine stall by manually opening the valve you need to either replace the valve or clean out the EGR passage in the intake manifold/cylinder head.

Chris