1986 Mazda B2000 Cruise Hesitation

1986 MAZDA TRUCK

1989CAMARORS

MEMBER
2 POSTS

Hey, I have a 1986 Mazda b2000 LX short bed 5 speed manual transmission with only 80,000 miles. It runs great other than my small engine problem. The engine hesitates/shakes/jerks/pulsates when at around 2400 rpm- 3300 rpm when cruising steadily on the gas(this doesnt happen when the engine is cold, only after it reaches normal operating temperature). I checked out a Technical Service Bullitin about the subject on "All Data" and "Shop Key"and it says it needs some new modified parts. The problem is within the EGR System is what it is leading me to? Any help/suggestions would be very appreciative. Thanks alot.[b:a8cb884bf1][/b:a8cb884bf1][b:a8cb884bf1][/b:a8cb884bf1]v

Feb 8, 2006 at 4:12 PM

GLASSMAN55TB

MEMBER
1 POST

I had B200 that had the same problem. There are three reed valves in the front of the air cleaner that control gases from the exhaust system. They are a dealer item only, well they were when I had mine. It's worth checking into. You also might check the vacuume advance diafram on the distributor this also causes hesitation.
Good luck,
Tony.

Feb 9, 2006 at 4:52 PM

COSMO

✓Experienced Mechanic
347 POSTS

That sounds like a perfect symptom of the idle mixture solenoid. The sensor cannot be seen from the outside of the carb. The only thing you can see is two green wires coming out of the top of the carb when the air cleaner is off. Let me guess you have a stuble or hick-up around 100kph/65mph?

This could be a good posiblity

Cosmo..Mazda Tech

Feb 13, 2006 at 12:10 PM

1989CAMARORS

MEMBER
2 POSTS

Yes it does do it around 65mph. Is there a way to test the component? About how much does it cost? What would some other symtoms be? The engine kind of does it (hesitates) around any speed that is around 2000-3500 rpms while I am steady on the throttle and it doesnt matter whether the engine is under load or not it still does it. The only time that it doesnt seem to do it is when the engine is cold/not warmed up. I feel it has to do with the carb. Any more help would be appreciative. Thanks ALOT![/b]

Feb 13, 2006 at 4:35 PM

COSMO

✓Experienced Mechanic
347 POSTS

There is no real way to test this component. It was a TSB about ten years ago. You can replace it on the vehicle, you only need to take the top of the carb apart. This can be done, but you should take it to a Mazda dealer unless you are very very very very familiar with Mazda carbs and their settings., because after this you will need to set-up the carb and all the mixture settings.

Cosmo...Mazda Tech

Feb 13, 2006 at 9:47 PM

HELLCAT18

MEMBER
21 POSTS

My suggestion would be to replace the carburetor with one from another Mazda, preferably one that just found it's way to a junkyard... Most of the cars that are brought in from accidents will have good working components.

Mar 29, 2007 at 4:30 PM

HELLCAT18

MEMBER
21 POSTS

Sorry, but I forgot to mention this.... My Mazda b2000 had the same problem when I bought it used. The problem turned out to be a broken, cross-threaded spark-plug in the number 3 cylinder. Check that your spark-plugs are all in correctly and gaped, as that WILL cause hesitation in the engine. Also a side note, you don't HAVE to replace the reed valves usually, just take the filters out of the rubber gromit and the metal casing (don't worry about breaking anything but the rubber if it's dry, they are made to come apart) and wash out the filters with a strong anti oil dish soap. They should be a light brown when clean. When they are dry, put it all back together and fire it up! You should see a noticeable improvement in performance if they were oily or full of dead bug parts.

Mar 29, 2007 at 10:25 PM

86MAZDAB2000

MEMBER
1 POST

Hi, I realize this thread is older. I am having the same issues, jerking, hesitating, occasional stalling at lower RPM, but only in gear and driving, from second gear (5 speed standard) to 65MPH in 5th. It seemed like vapor lock at first (100 degrees) but then just does it even with the engine temperature and weather cool. I replaced the spark plugs and ignition wires. I am having a hard time finding the reed valves, to clean or replace (at the front of the air filter housing?) Also, could this possibly be a clogged fuel filter or fuel pump failing? Just curious what my next steps should be. Thanks for any help you can provide, I appreciate your time. :) P.S. It has a new timing belt, water pump, starter, coolant hoses, thermostat, not that this is relevant, just trying to supply information.

Aug 7, 2012 at 7:51 PM

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Suggested Repair

Have a Mazda dealer replace the carburetor idle mixture solenoid, identified by two green wires at the top of the carburetor. There is no reliable test; an older TSB covers this warm-engine cruise hesitation. After replacement, the carburetor and mixture settings must be reset by someone familiar with Mazda carburetors.

Conversation Summary

A 1986 Mazda B2000 owner reported hesitation, shaking, and jerking at about 2400-3300 rpm while cruising at steady throttle, only after the engine warmed up, and suspected the EGR system from a TSB. Other owners suggested air-cleaner reed valves, the distributor vacuum-advance diaphragm, a used carburetor, spark-plug installation, or cleaning reed-valve filters. A Mazda technician said the symptom, including a stumble near 65 mph, matches a faulty idle mixture solenoid that cannot be tested and should be replaced with a full carburetor mixture setup afterward.

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1986 Mazda B2000 Cruise Hesitation

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