Toyota Repair: Failed Oregon Smog Test... What to do?, smog test station, ppm 220

Question
Hello Mike,

I have a 1988 Toyota 1 ton truck with a 22R-E (EFI) engine (it is
a mini-Dolphin motor home). I took it for its 2-year Oregon
smog test and it failed with these reults:

HC PPM (220 MAX) - 578 (1st idle) / 1566 (@2500 rpm)
CO(%) (1.00 MAX) - 0.27 (1st idle) / 1.45 (@2500 rpm)

I then put in a set of new Bosch platinum spark plugs and new
spark plug wires, and a new distributor cap and rotor. I also
filled my gas tank with hi-test gas, whereas I normally use
regular unleaded. Then I went back to the smog test station and
got these results... better, but still not passing, due only to high
results for HC @ 2500 RPM:

HC PPM (220 MAX) - 150 (1st idle) / 734 (@2500 rpm)
CO(%) (1.00 MAX) - 0.11 (1st idle) / 0.54 (@2500 rpm)

Btw, my other vehicle is a 1994 Toyota p/u 22R-E, and it passed
its last smog test with these results:

HC PPM (220 MAX) - 4 (1st idle) / 11 (@2500 rpm)
CO(%) (1.00 MAX) - 0.00 (1st idle) / 0.14 (@2500 rpm)

... so I can see that my Motorhome engine could be running
*much* cleaner (and better)!

I would appreciate any help/suggestions you could offer in
fixing current problems in my Motorhome's engine, so I can pass
the Oregon smog test *and* have a better running, more fuel
efficient engine.

Also, any tips you might have on additives to use (or not use)
and other "protocols" before getting my next smog test, would
be greatly appreciated!

Thanks!
Larry


Answer
I would suspect that the motor home doesnt get the use that the other truck does.
Try changing the engine oil. The new oil will be able to absorb some of the HC. also make sure to have a new PCV valve in it. Take her for a long ride and get her hot. When its not used as much as a standard vehile you can also get some carbon build up in the combustion chamber. Try some "carbon buster" type cleaner. Available at a parts store.
If it runs fine on regular fuel DONT use high test. high test burns slower and not burn all the fuel in the cyliner during a ignition cycle. It can actually increase Hc and CO in a vehicle designed to run on regular fuel.
I would suggest using ONLY NGK or Nippondenso plugs that are for that engine.

Mike