I have recently purchased a 1991 Mazda B2200 LE extended cab, 5 speed with carbs. The truck has two issues. The first, when I bought the truck I noticed it would idle real low after it warmed up to the point of dying or almost dying. I changed the fuel filter and put premium gas in with fuel cleaner. Still didn't ilde right. I then had a retired mechanic tell me that it probably needed to have the motor cleaned. He dumped some automatic tansmission fluid in the carbs. When he was done the car ran and idled great for about a day. Now I'm back to a poor idle again. Any ideas.

The second item is the brakes. I have found that when I do any amount of city driving the front brake appear to clamp shut on the rotors and you can begin to smell burnt breaks. If you let the truck cool down for about 20 minutes the brakes release. Is this a caliper problem, or could it be breaklines? How would you know if the master cyliner is going out?

Please help as I'm pulling my hair out

 

First, I think that a carb rebuild will do you all kinds of good. On top of that, you may have a clogged cat. I am leaning towards a rich mixture due to the carb.

The brakes thing; I think that it is a bent piston in the caliper. A rebuild might do a bit of good here also.

 

There is actually more bad news. Because of the fact that it ran better after the ATF treatment, I think that you may have problems with compression due to bad rings.

 

First the brakes, have had the same issue in the past about brakes lock down after some driving. This occurred after I had replaced the brake master cylinder, and it was due to lack of free play in the brake booster push rod, so I needed to adjust that shorter. You can unbolt the master cylinder, then carefully pull it (without disconnecting the fluid lines) towards front of the truck to adjust that booster pushrod. I used a bent-needlenose vise grip to hold the rod, and then loosened its locknut, then adjusted, then re-bolt the master cylinder, no need to bleed the brakes. Now I know to match up the depth and to adjust whenever I replace a master cylinder. If you don't have power brakes, then find the pedal pushrod and ajust similarly.

Now for the carb: congratulations, you have the most complicated carburetor in the history of mankind, and it's 19 years old. It wouldn't hurt to get some compression numbers, but carb issues on theses trucks are common (I myself have a Weber 32.36 DGEV on my '88 B2200).

 

Thanks for the suggestions and ideas. I found that both calipers were shot, so I replaced them and put new brake pads on. The idle appears to be better after finding one of the spark plug wires was cracked and arching. Replaced all the wires and adjusted the idle to 1100 and it appears to be staying where it was set when idling.

How may RPM's should it be running at idle speed? I was guessing between 800 and 1000, is that correct?

 

you should have your idle adjusted down to about 800 rpm