Does anyone know what the timing should be for a 93 B2200? Thanks!

 

I believe it is 6 defrees before tdc +-3 dgrees. Power time it though. Advance the timing til it clatters on accel then back it off a dgree at a time til you get no clatter. That is optimum timing foryour fuel,altitude,humidity etc.

 

Cool, thanks, that is one of the things i am about to check on this truck. I bought it from a guy that said it started running a lil rough and his mechanic said it was the O2 sensor, makes since, but i want to go ahead and check everything. Thanks again for that tip!

 

Not likely the o2 sensor. You can disconnect it and it will go into open loop and fixed duty to verify it. I would clean the egr valve real good. If it sticks open it sucks #3 cylinder dry because it uses that intake runner. Run some Techron or Seafoam in the gas tank to clean up carbon on the valves and pistons plus it has an air/fuel solonoid in the carb. Kinda like an injector that can stick.

 

Thanks again! So are you saying that if i disconnect the O2 sensor, it will just act as if I didn't have one? Not sure I undertand the "fixed duty" part. Is it trying to do a system check? Anyway, according to the guy I got the truck from, if was fine one week, then the next, it just started getting terrible gas mileage. I haven't had a chance to really start looking, just trying to get some general input first. I am not at all familiar with this type truck, done alot of work elsewhere, just not on a mazda. Thanks again for the help!

 

Cars run what is called closed loop. This uses inputs from sensors to allow the ECU/PCM to adjust fuel mixture/timing/dwell etc to obtain 14.7 :1 air/fuel ratio,which is the perfect air/fuel ratio for combustion of a gasoline engine. When an input is disconnected or goes bad it has a failsafe which basicly is a fixed setting for air/fuel/timing etc so that the vehicle can be driven. An o2 sensor input is ignored at idle anyway even though you see it changing readings at idle it is only putting out millivolts. The ECU/PCM wants to see actual volts like 1 volt or so whichthe o2 can only achieve at higher temperatures which occur above idle around 2500 rpm.
That said your truck has a carb and they are a bit tricky and by no means trouble free. The fuel mixture adjust screw has an anti-tamper pin at the base of the carb which you will need to remove to adjust it.This is for idle mixture adjustment.It also contains an injector of sorts in the top of the carb . The idle mixtureis set using a dwell meter. It should read 40 to 70 degrees dwell at idle and fluctuate back and forth between those readings. The test tap for the dwell meter is on the passenger fender near the firewall. It is a single wire. I think green connector. Maybe brown. Sorry it has been awhile since i messed with one.
It is very hard to help on some things via the internet. To fix it you will have to inspect each system individually.I would start with the EGR valve and Techron or Seafoam in the gas tank.

 

Cool, I can understand that. I was not at all familiar about the carb on this truck, however, that will definetly get me started. Thanks again and I will give it a try! You definetly seem to know a thing or two about these mazdas.

 

If the truck has been sitting for about a year (not running) what would you say would be the first thing to check if it won't start?

 

Fuel quality/fuel filter probably.

 

that was the first thing i did, was change the fuel filter and drain the tank.