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normanahoyt, ASE Master Tech
Category: Mazda
Satisfied Customers: 371
Experience:  I am a Mazda Master Tech
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1998 mazda b4000: between 1500..1500-2000 RPM under load..Coil Pack

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I have a 1998 Mazda B400, 4.0V6, it hesatates between 1500-2000 RPM under load. I have replaced the Coil Pack and #3&4 Plugs and wires. What else could it be?

Can you get codes from the computer for me?

There are parts stores that will retrieve codes for you and if you pass those on to me it will help immensly.

Customer: replied 6 years ago.

I retreived these codes; P0306, P0303, P0125. I filled ther cooling system because it was low and the over flow jug was empty. Cleared the codes and the Check engine Light came back on on the way home which is aXXXXXfrom the parts store.




P0306 is a misfire on #6 cylinder.

P0303 is a misfire on #3 cylinder

P0125 is excessive time to enter closed loop.

At this point there are a number of items that it could be. I hate to run you back to the parts store but it would be helpful to see if P0303 came back. If it didnt' and P0306 did then finish changing your plugs and wires as doing part of the job can be "shooting yourself in the foot"

If P0303 did come back then I believe we need to look for a vacuum leak first. Spraying carb lean near at the seam of the cylinder head and the intake next to #3 and #6 cylinders can help you find a vacuum leak....just be careful that you do not spray on spark plug wires or anywhere near the high voltage as it will result in a fire.

If the engine reacts to carb clean in those areas then your intake manifold gasket will need replaced.

The third code was probably set by low biggest concern at this time is "why was the coolant low". These are prone to head gaskets and cracked heads so I would want to find a leak and fix it and if it is not an external leak I would not proceed with diagnostics until that is resolved as coolant entering the cylinder will also cause a misfire under certain conditions.

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