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Discussion Starter · #1 ·
I have the 1987 B2200 and I have carb problems. like I get a good idle before driving, but maybe 10mins later when I come to a stop, the engine stalls, every single time I stop. I know its a probably a vacuum problem somewhere but I dont know where to look, I don't know what air valve does what and if its related to the idle of the carb. Can someone help me? Just telling me where to look. Thanks!


L.Leblanc
 

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Simon - I'd check the EGR valve. If the EGR is stuck open or partially open, same will happen. I use a hand vacuum pump to test, and I've had that happen.
 

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Discussion Starter · #5 ·
Yes, could be a vacuum line, anywhere. The ends get hard with time and heat and then become loose and can "appear" to be OK but are not.
So I haven't had the time to check all my vacuum lines (I will do it this weekend) but I have some more info. First, when I start it cold, the choke doesn't come on. I adjusted the choke speed multiple times and I see that the choke plate in the carb is closed. When its cold, the truck runs at the normal idle speed, wich is set at 1000RPM. Then, when the truck is heated up a little bit, it doesn't keep its idle anymore so its probably heat related. If I try to get the idle speed up to 1000 (I have to do like 2 full turns or more) It varies as much as 500RPM. So I know the problem comes from something that opens up when the truck is warm. Does that change your perception of the problem? still the EGR? I have a video of the idle if you want it.
 

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Discussion Starter · #6 · (Edited)
Just tested the EGR with carb cleaner, it isn't stuck open and its moving freely so its probably not the valve itself. Then again, could the valve open as normal when I drive down a road but when I come to a stop it stays open even if its free to move? Can I disconnect and plug the vacuum line to the EGR valve so that it stays closed and then see if the problem comes again? Im really not sure.
 

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When cold, choke butterfly should be essentially horizontal. After like 5 full minutes, choke butterfly should be essentially vertical. Check that.
 

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1986 Mazda B2000 SE-5 Long Bed
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For the choke to engage, you have to push the accelerator all the way down ONCE. If it is not closing when first cranking this could be part of the issue. Cussboy's advice is key here.
A stuck EGR valve can cause this problem as well as the idle solenoid. The EGR valves are controlled by the computer and if the computer is failing an output test they might not be closing. If you have a test light handy, follow the procedure in the service manual on Mazda Minitruckin to retrieve codes. The computer can tell when it fails an output test.
To bypass the EGR system you need to remove both lines, for No.1 and No.2 air valves. The No.1 air valve is a plastic diaphragm underneath the air cleaner and the No.2 air valve is the metal assembly attached to the air cleaner. Both of these lines should be removed and capped off AT their solenoids on the passenger side fender.
This will cause the EGR valve to be commanded CLOSED at all times.

Idle solenoid could be causing this if you have power steering, AC, cruise control, or the automatic transmission. The computer will try to idle up under these load conditions and if the valve is not working or if the computer is incorrectly commanding it will not work. Make sure your idle stop switch is working as well (OFF idle ON >1500rpm)

Correct idle for these trucks with the manual gearbox is 800rpm and 850rpm with the automatic, measured with all loads off in Park/neutral on a level surface, engine warm.
 

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The earlier models (1982) has thermocontrolled vacuum switches under the water heated intake. They open vacuum (to EGR and purge control valve) at engine warm temperature. If one of those lines is cracked or has come off, youll get a massive vacuum leak when the the motor gets warm. You wont notice it until you come back down to idle and itll crap out. Also check function of carb idle solenoid if equipped. It kicks idle up and the vacuum source releases throttle when engine RPM is down to idle. I think its to prevent the throttle from snapping closed and causing a momentary rich condition upon deceleration. Check if your throttle is up on its idle stop when the car dies. Maybe you artificially adjusted curb idle with this thing operating and when it randomly releases, your carb drops to true curb idle that is too low?
 

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1991 Mazda B2200
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I had a 87' B2200 also that had some similar problems. Not sure it is a fix for your problem, but maybe. I had a similar problem of stalling, couldn't figure it out. Finally pulled the plugs and they were burning super lean. Tried adjusting the factory carb with no luck, so decided to rebuild the carb....mistake trying to rebuild the carb. I have rebuilt a lot of carbs in my lifetime, but this one pissed me off so bad I threw it on the ground . Decided to go with a Weber carb. Wasn't too bad putting the carb on, and it was oh so much fun getting rid of all the EGR crap. Really looked clean under the hood when I was done. Well, I had the same problem even with the new Weber carb, what the heck. I read somewhere the problem might be my catalytic converter. So, punched it out to straight thru, but still had the same problem. Dummy me, was looking at my Haynes manual at the exhaust system and lo and behold, I never knew there was another catalytic that was a part of the exhaust header attached to the exhaust manifold. Took the exhaust manifold off and there was my problem in the exhaust header chamber for the catalytic converter. The catalytic converter material had broken into pieces and dropped into the exhaust header almost completely plugging it up. The exhaust back pressure was causing the "lean condition" in the engine, hence the stalling and other issues. Well, bought and put on a new set of headers and after that everything was "perfect". Loved the Weber, headers, some additional horsepower, and the sweet sounding exhaust.
 
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