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Help! 4.0 OHV Stuttering/ CYL 6 misfire

428CJ

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Oct 23, 2013
Messages
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Location
Boise, ID
Vehicle Year
1997
Make / Model
Mazda
Engine Size
4.0
Transmission
Manual
My dad's 1997 B4000 has developed a severe misfire on the 6th cylinder and is almost undriveable from the subsequent stuttering and hesitations, especially when their is more load on the engine. It has been cold starting a bit harder than it used to, and the stutter has been getting worse with time. We bought it in July and sometimes it would cut out for a split second in third when accelerating. Now it stutters and shakes and hardly accelerates in all gears, especially above 1st.

So far, we have changed:

-All new Autolite plugs.
-New Fuel filter
-New plug wires (the obscenely expense motorcraft ones).
-Sprayed the MAF with MAF cleaner because the MAF looks like it is integrated into the intake tract.
-New coil and cleaned up the old coil contacts. Neither helped.
-New Air filter
- 1/2 can of seafoam in gas tank.

The 6th cyl doesn't seem to be firing at all because the plug looks brand new, but is getting spark.

We are thinking that perhaps the 6th cyl fuel injector is bad or clogged, the lower intake gasket(s) is leaking, or the cam or crank position sensors need replaced.

Anyone have any insight or expierence with this problem. It doesn't always through the cyl 6 misfire code, but always stutters and misses btw.

Thanks.
 


aspevacek

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Jul 10, 2009
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Location
Harrisburg PA
Vehicle Year
97
Make / Model
Ford
Engine Size
4.0 OHV
Transmission
Automatic
Get a can of brake cleaner and with the mother running spray around the intake where the intake bolts to the heads and around the upper and lower intake. See if the engine idle goes up, smoothes out or the engine dies.

have all engine codes pulled and see what codes you are getting.

do a compression test on all cylinders.
do not look for how high the numbers are but rather the amount between the highest and lowest numbers.

you could hook a noid light to the number 6 injector connector to ensure it is getting the pulse from the computer. another thing is you can use a long screw driver against the injector and use it as a stethoscope.
 

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