3.0 hard miss fire

[hr8882]

I have a 2002 ranger 3.0 RWD that has a intermittent bad miss at idle and at cruising on highway [ low load ] NO codes. complete tune up done 15,000 miles before this. New coil 3 years ago . When miss happens the tachometer does change. It does act like a cam sensor but was wondering about the cam sensor synchronizer itself shaft chatter. it is not making any squealing or any other noise that I can hear. Any techs got some input as to what it may be? Thanks

 

[RonD]

Misfires at idle can be dirty injector tips, can of Seafoam in the gas tank can take that off the table, good to do that once a year in any case
Dirty tips DRIP fuel instead of spraying it, so you get a poor mix under low load(short open time for injectors)

Also clean MAF sensor, once a year

CAM sensor/synchro for the 3.0ls was an issue, never have read a reason for it, I would just plan on changing the sensor/synchro out as general maintenance every 80-100k miles
Same as upstream O2 sensors every 100k miles or 12 years, which ever comes first, they run out of chemicals to detect Oxygen and cause a drop on MPG and eventually will set codes, but the drop in MPG is a bigger deal since that's MONEY out of your pocket which could have paid for the new O2s, lol

Ultimately when there are misfires you should start with a compression test FIRST
Cold engine
All spark plugs removed
Press gas pedal to the floor while cranking, this turns off injectors and also gives full air flow
Test each cylinder, get at least 5 or 6 "hits"
write down results

3.0l should be running 160psi compression, but testing parameters vary, so its more about the average number and the difference of that number to the lowest numbers

You can end up chasing your tail with fuel and spark as far as a misfire, so taking compression off the table FIRST is best, because if it is the problem the money and time spent on spark and fuel was wasted

 

[hr8882]

Thanks for the input. I forgot to mention my truck has 132000 miles on it. I'm really anal about oil changes every 3500 miles . I'm not one to be a part changer. I like to find out what causes a issue.I have a good scan tool but it lacks a live graph which would help.

 

[RonD]

At 132k I would swap out the cam/synchro and both upstream O2s just as general maintenance
Also PCV Valve every 3 to 4 oil changes

Cam sensor may cause misfire but would expect a code if that was the issue
O2s wouldn't but you will see better MPG for sure

Compression test just to take that off the table or find out it is the misfire issue