1986 Masda B2000 idle


My B2000 truck will not come out of fast idle.
This seems to be something that happened after I had the air cleaner off.
All the vacuum lines appear to be connected.

Any thoughts?.

Choke thermostat. They don’t work after so many years. If you replace the top of the carburetor you will have a new one. That costs over 400 dollars and had to be ordered from Japan the last time I had one changed. If you have debris in the way, you’ll have to get it off the linkage and maybe a vacuum line is misrouted and getting in the way.

I can open the choke manually and it does not slow down the engine speed.
But I will check the other items you mentioned. Thanks

I looked at all the linkage and vacuum lines and they all look fine.
I drove the truck and once the engne warms up, it idles fine.
I assume this means that the choke assembly needs replaced, which as you mentioned, seems to include the top portion of the carburetor.

I can open the choke manually and it does not slow down the engine speed.

When you did this, did you aso blip the throttle to release the idle step-up cam (if your carb has one)? That cam might be hanging up.

You can also adjust the fast idle speed so that it doesn’t drive you crazy. There is a little screw for that on the fast idle cam. The cam is more of a step than a cam. I had to adjust my Mazda pickup so that I could get fast idle when cold. You will find it. Don’t try to adjust the choke thermostat because it doesn’t move. It will break. It will still work but it will change the fuel meter setting which also can’t be replaced without changing the carburetor top.

I basically agree with pleasedodgevan, but before making any adjustments, I’d suggest that you try cleaning the linkage for the high idle cam. The way the system works is that a bimetallic spring opens the choke when the engine warms, and it also moves linkage that pulls “steps” under a “high idle screw” that allows the throttle plate to open some increasing idle speed. It’s common for these mechanical parts to get gummed up and to get worn as they get old, causing the high idle system to not come down once engaged.

It’s also not uncommon for the throttle plate shaft to wear grooves over the years, causing the throttle plate to stick open. Correcting this requires a partial carburetor rebuild. If with the mechanism cleaned and the bimetallic spring changed you still have the problem, this is a possibility to consider.

I have clean everything and it seems to be working fine. I guess it is kind of like a British sports car in that it seems to have fixed itself.
Thanks everyone for the comments.

Congratulations on a successful repair. It’s good to hear that a good cleaning was all it needed.
Happy motoring.