Questions and Answers

Toyota Fails The Test

Q. Failed (first time ever) emissions test twice! Everything passes except the CO rates too high when they go to 2900+rpm's. I went back and reset idle speeds, fast idle etc. I figured it was probably the high idle as it was out of specs and reset it accordingly, etc., etc.

Manufacture date is 1983 Toyota Tercel Auto trans., A/C, P/S, 1.5 liter 3AC engine. I use ONLY 93 octane gas and do all the good stuff regularity since day one.

Now, two things:
First I didn't bother to replace the air filter, the spark plugs (Bosch platinum made for this model and NOT the expensive ones), nor did I change the oil & filter and PCV valve before going in. Why? All were relatively new.

Secondly my throttle positioner screw has, for the last 7 years, surged to higher rpm when I try to achieve the standard 1400 rpm's. Over the years I've just gotten as close to 1400 rpm as possible and still have the TP bring the rpm BACK down to curb idle.

I've NEVER EVER had this problem, so I am puzzled. It's just high CO at high rpm's ONLY! The ratios for telling if the catalytic converter is dead are FINE!

Do you think changing the oil etc would do the trick?

Thanks and PLEASE answer me quickly, I have only a couple of DAYS until I get a ticket while driving!

Hg

A. I have done some experiments on different brands of spark plugs over the years. I wanted to see if there were, indeed, any differences and if there was a correlation between brands and makes of cars. These experiments have shown me that there is a difference in brands and while one brand would work well in one make of car, it would do poorly in another.I don't know the whys and wherefore, just that some work in this car and not in others.

I have found that Japanese cars do not like AC, MotorCraft, Champion or Bosch spark plugs. I have found the best plugs to use in a Japanese car are NGK's. I have seen, time after time, a drastic reduction in emissions just from changing to NGK's. Quite often enough to pass any emission test. When I diagnosis a performance problem on a Japanese car, the FIRST thing I do is put in a new set of NGK's. I used NGK's in all the Datsun/Nissan cars I have ever owned since 1973 (and that's quite a few) and none of them has ever failed an emission test.

I would do a quick plug swap and see what happens, if that doesn't help, then I would look at the fuel system. There are adjustments that are made that can only be made by a dealer. I know of one adjustment that takes three pages of the Toyota service manual to perform because of the connections and bypasses that need to be made to do the adjustment accurately.