I have a 1990 mazda B2200 P/U with a carburetor that won't idle when warm. It starts fine and idles at around 1000/1100 rpm. When you come to a stop it idles at about 500rpm, runs rough and then dies. It will start right up again but you have to keep it idling at about a 1000 or it will die again. It seems to run great at all power settings above this rpm. I've changed the fuel and air filters and sprayed some carb cleaner in it to no avail. Anybody else run into this problem? Thanks

 

is there a float level on that carb? or an idle air adjustment?

 

I'm not sure about the float level but the idle mixture is preset at the factory and sealed. So no adjustment there.

 

Did this happen all of the sudden and has been running fine before or are you new owner? If happened all of the sudden I would be first suspect of the mixture contol solenoid in the carburetor. They have a nasty habit of sticking and causing the conditions you describe. The solenoid is what controls fuel mixture in response to changing signals from the oxygen sensor in the exhaust. If you have a dwell meter there is a way to look at the solenoid on/off time and see if it is sticking or not. You might also pull the air cleaner cover off and with then engine idling, lightly tap the top of the carburetor that you can see and see if idle suddenly improves or changes. This will sometimes 'unstick' the solenoid for a bit and let it operate normally.

 

I've been driving the truck for about 5mo now and this problem just started happening, before everything was fine. I'll try tapping the solenoid or the carburetor and see it it makes a difference. Are these mixture control solenoids independent of the carburetor or do you have to order a carburetor/carburetor rebuild kit to remedy the problem. Thanks for your feed back this sounds like it very likely could be the problem.

 

Used to have to get the entire top of the carb in order to get but Mazda made available as a separate repair kit in early 90's. Part number is F240-13-X33 and shows retail of $206. Make sure to get carb top gasket as well. It is not included in the kit. Lets make sure this is what it is though first.

 

I have the same damn problem!! I went through the haynes book it says do this and that and I did it all now its an old truck 86 which I am trying to fix up and it need the parts but this thing has been driving me crazy!! I will just buy a new carb wanted to get a weber any ways. If this doesnt remedy the problem do you know of anything else this could be?? I have changed plugs,wires, distributor cap, rotor, coil, fuel filter check for vacuum leaks I did find one which it improved it a little but didnt fix it so I guess that was part of the problem. I cant find any shorts any where or can I find any bad wires any where....I am stumped!! I was thinking maybe the fuel pump but I would have to put it in the shop for that I do not know how to change one of those out but thats going to be probably $300 to have a shop do that now if I wanted a high preformance pump or something like that I would just change it anyways but I dont (never even heard of one) so I kinda dont want to waste the money and then this not be the problem. Any help would be great. It just started doing this about a week ago.

 

Do you have a dwell meter? Can pick one up from any parts store for fairly low price if you don't. On the passenger side of the vehicle behind the right strut mount there will be a white connector that is just hanging there not connected to anything. The wire is brown with a yellow strip on it and has a white one pin connetor on the end of it. Hook the red lead of your dwell meter up to this wire and the black wire up to negative post of battery. You are now watching the on/off time of you mixture control solenoid of the carburetor.
After getting engine good and warm (hold rpm at 2500 for 3 minutes andtheh let idle for a minute ). The reading should fluctuate slowly around the 45' mark. If needle works up to high or low end of scale and then suddenly jumps to 30' or so and stays then there is a mixture control problem. Try this and see what happens. Post back with results. Most probable is fault with mixuture contol solenoid but there are other problems that can devolpe.

 

Ok guys got power back to the mazda!!! I never actually changed the plugs because the guy I got it from said he just changed them a couple days before I got it he had a tune up done! Yeah right! So anyways the guy must have been mistaken!! Because these damn plugs looked like the orignial plugs one broke off in the engine!!! That was a pain in the ***!! One was pretty easy to get out but the other 3 took a bit of time. When I did finally get the other 3 out the threads looked warped I mean bad now wonder they were so damn hard to get out. Well it took me about 2 hr but I got the one out that broke off. With out having to take the engine apart which if that happened I would have had to call my friend. I had to retap the holes for the spark plugs. Once I did that they went in nice and smoothly!! Truck runs good now it has power but the idle still sucks keeps droping down to 500 and tries to die out on me so I will get the dwell meter and check this out.

 

I'm going to try the dwell meter approach and see what I come up with - would a sticking EGR valve cause these idle problems? I've read on some of the other sites where these things get carboned up and cause the valve to stick or block vaccuum passages. Anyhow I'm going to try and clean the EGR valve with some carb cleaner and see if I have a blockage problem if the mixture control solenoid checks out. I'll let you know what the results are.