I know it doesn't happen all that often but it is possible.

Ok so heres the rundown:

Sammi runs pretty good (high idle and hesitation but I will fix those later) except it wont pass smog. Fails NOx because I live in California! So I'm pretty sure its running lean since everything else is way low. Took it to school and let the engine diagnostic guys check it out and they say that the mixture control solenoid is not receiving pulses from the ECM. Has anyone ever had this problem? Don't want to replace $200-300 computer for no reason. Also I'm pretty handy with circuits and was thinking about replacing the transistor that is supposed to fire the MCS.

Any and all (reasonable) suggestions will be considered AND appreciated!

Here are the results in case anyone was wondering:

15mph  [11.8% CO2] [4.0% O2] [HC(ppm) max/measured 146/23]PASS [CO 1.00/0.00]PASS [NOx 1096/1681]FAIL

25mph [12.6% CO2] [2.8% O2] [HC 126/13]PASS [CO 1.22/0.00]PASS [NOx 956/1470]FAIL

Nox are created from the fuel burning too hot and too fast, so they added the EGR
to introduce exhaust into the intake system, which slows the burn rate and reduces
your Nox levels.

I don't think your MCS is firing because it doesn't need to, the engine looks to be
running great by the numbers, there are two things to look at tho, one being the
Cat, if it is a 3 way it will reduce Nox, HC and CO, it could be out of spec, and the
other thing, and what is probably not doing it's job is the EGR system, it is common
in these older trucks for the passage from the exhaust side that passes through the
back of the head and into the intake manifold to get plugged with carbon, effectively
disabling the EGR so it cannot reduce your Nox as designed, so clean that passage.

You will probably need to remove the exhaust and maybe the intake to do the cleaning,
get some carb cleaner, or your favorite spray and a long brush like a gun bore brush, you
might need to even drill out some of the packed carbon, but be careful of the aluminum,
you wouldn't want to drill into the cooling passages

Good Luck
Wild

Thank you for checking out my thread!

I'm going to give that a shot today as it has been one of my suspicions, as well as the three way valve thingy.

The cat was new in November but could be toast by now I guess.

Just found my timing light and dwell meter too, so if the EGR passage is fine I will be doing some adjusting.

Defiantly retard your timing, you are allowed 2* either way, take it to the
max retard timing that is allowed, that will help too.

As far as the Cat, it should be fine with the #s your truck is blowing, so
never mind the Cat, clean the passage that feeds the EGR, and retard the
timing and it should pass the NOX test

Keep us posted and Welcome to ZukiWorld

Wild

Defiantly retard your timing, you are allowed 2* either way, take it to the
max retard timing that is allowed, that will help too.

As far as the Cat, it should be fine with the #s your truck is blowing, so
never mind the Cat, clean the passage that feeds the EGR, and retard the
timing and it should pass the NOX test

Keep us posted and Welcome to ZukiWorld

Wild

Yes clean that passage into the EGR they get pretty gunked up.  Mine was almost completely clogged.

If you're handy with electronics then pull the ECU and replace any electrolytic caps, they will all be past the end of their service life by now.

I just went through this same problem and also am in CA.  What part of CA are you in?  If your close by, I'd be happy to help you out.

If your egr ports are clean, are you sure the egr valve itself is working?  Mine was bad and it made a marked improvement in the NoX readings when replaced.

IT PASSED!!!

Such a weight off my shoulders

Ok so I pulled the EGR and its was almost completely blocked but the diaphragm was still good. So I cleaned it out as well as the passage (about as good as I could without pulling the intake manifold off) and threw on a new gasket. The flow improved pretty significantly so I was pretty happy with that.

Next I changed the timing to about 8^o BTDC and the motor seemed to like that a lot. Then I fiddled here and there, couple new vacuum lines, tightened the accelerator cable, etc.

Finished it off with some Seafoam and after I cleaned up the plugs since Seafoam has a tendency to fowl them.

Heres the new results:

	%CO2	%O2	HC Max/Meas	CO Max/Meas	NOx Max/Meas
15mph	12.0	4.0	146/88	1.00/0.07	1096/440	PASS
25mph	12.6	3.1	126/28	1.22/0.00	956/953	PASS

Thank you for all your suggestions!

As for the caps, I already looked at them and they look like a different type than the ones that always blow up so I opted not to swap them out. I think I might get a megasquirt and a throttlebody to start playing around. That way I wont even have to deal with blowing caps, bad transistors, and mixture control solenoids that wont fire!

Thanks again,
-Z

lol, you SQUEEKED by on the 25mph NOx reading.

I know right?!

I think I could drop the 25mph NO_x numbers if I pulled the intake manifold and gave it, as well as the cylinder head, a proper cleaning.

Has anyone ever done this? Any tips tricks and/or photos would be great!

I just went through this same problem and also am in CA.  What part of CA are you in?  If your close by, I'd be happy to help you out.

If your egr ports are clean, are you sure the egr valve itself is working?  Mine was bad and it made a marked improvement in the NoX readings when replaced.

Hey oak_raid thanks for the offer! That right there is pretty much why I wanted to get into samurais and off roading.

I'm in southern California, about 30 min east of LA. Are you anywhere close?

I'm in the Bay Area.  About 30 minutes east of Oakland. 

I'm out in Beaumont, Zizzac, you must be about the Riverside or Corona area

Wild

Hey guys! Sorry but this month has been crazy. I'm actually about 25-30 out of la off the 210 not the 10. So that puts me in Glendora. Never heard of it? Nobody has! Haha!

Well I will actually be moving up to the quasi-bay area of Davis, Ca in the fall. Maybe we can do some mild off-roading up there (I have no idea where any trails are up there) but we would have to keep in mind that this is my daily driver and I'm a starving student!

While I'm down here I would love to see what's happening out in the IE as well!

Thanks again guys! Talk to you soon.

-Z