Questions and Answers
B-2000 Emissions
Q. Hello Vincent! Since I have spoken with you my car has been running like a top!
1987 Mazda B-2000
2.0 liter
Manual transmission
197,000 miles
Carb
NO P/S or A/CI took it for inspection. It failed for emissions: HC just over, CO% at twice the limit. I have four questions:
1) I think I need to set the engine tach (800 curb idle is specified) however I can't find the lead for the tach! The Haynes manual indicates the LgB wire however I don't know where this wire is. Can you specify its location/color code?
2) Is RPM a function of timing or are they independent? If related which do I set first?
3) The choke is hung up by a cam on the throttle articulated axle of the carb. Furthermore, this cam is adjustable via a spring loaded screw. Adjustment of the cam revels two "steps" on the choke. What is the proper adjustment of this screw?
4) Other than the above do you have any thoughts on passing emissions, and suggestions for repair?
Sincerely,
RussellA. Okay Russ, by the numbers:
1) I'm assuming your meter doesn not have an inductive tach pickup. In that case you need to connect to the negative ( - ) side of the coil to get a tach reading.
2) Timing effects rpm so you should set the timing to 6 plus or minus 1 degree before TDC and then adjust the idle speed back to 800 rpm.
3) To properly adjust the fast idle. With a cold engine step on the pedal to set the choke and without stepping on the gas start the engine. The fast idle speed should be 1100 to 1200 rpm. If it isn't, use that screw to adjust the fast idle speed.
4) All of these things will effect the emissions to some extent. The biggest factor in the emission levels is the fuel mixture. To properly adjust the fuel mixture you need a four-gas analyzer. Once you have the timing and idle speed correct, you will need to take it to a shop that has a four-gas analyzer and have them adjust the mixture to pass inspection.
I would also recommend you using NGK spark plugs. They work best in Japanese engines and quite often will bring the emission levels down to passable levels.
Additional Information provided courtesy of ALLDATA
