2002 Mazda B3000 - Sounding like a miss
 

I hope I'm in the right place here, if not, please let me know. I have a bit of a problem which sounds and feels like a miss in my vehicle. I'm not sure how to diagnose it though. My father's a mechanic by trade so some of the things I did were done at his advice.

A few weeks ago my pickup started "bucking" when I began to accelerate. A little hesitation if you will. A little later I started feeling this "bucking" while idling. A couple of days after that I finally got my first code - a misfire in cylinder 3 (P0303). I went ahead and replaced plugs and wires as the vehicle has 75k on it and nothing had been done as far as general maintenance. After replacing the plugs and wires I'm experiencing no more, or fewer, problems while accelerating but idling is just rough, vehicle is "bucking", and acceleration from a stop, overall is very poor. It has not stalled yet, but frequently feels that way. My wife says its better with the AC off but the jury is out on that still. It might just be better by coincidence. Another code came on today which has been read as "misfire in cylinder 1 (P0301).

My father suggested I spray carburetor cleaner over air hoses, etc, to try and determine if there's a vacuum leak somewhere. I suppose the engine would momentarily change the way it's running. Did that, no change.

I also purchased the silly fuel injector cleaners. I doubt it will make a difference. But I have it and will use it shortly.

Looking at the engine I see nothing arcing or otherwise out of the ordinary.

What would cause a misfire code to jump cylinders like that? What sensors going bad would lead to a general "misfire" like this. Any ideas on the most common problems that would cause something like this. Or a good first place to look.

I'm no good at diagnostics but I am good at following directions. Please help me follow the trail of breadcrumbs my car is leaving for me :) This vehicle has been pretty reliable up until now.

You never said what type of engine is in there, 4 or 6 cyl, size?
With plugs wires, it is gas.
Plugs and wires tells me to investigate further in to distributor, ignition coil.
Change distributor cap and rotor if it has one.
Wonder if distributor advance is working.

Otherwise misfires can be caused by many things:

Vac Leaks
Wiring Issues
Spark Plugs(Even Fresh Spark Plugs That Are Crappy Quality.... E3 And Such)
Ignition Coils
Alternators (Search EMI)
MAFS
Injectors
Injector O-Rings
Intake Gaskets
TB Gaskets
PCV Hoses
PCV’s
Malfunctioning EGR
Malfunctioning CAS
O2 Sensors
Aftermarket Intakes
Intake Hoses
Vac Lines
Timing Chains
Timing Chain Tensioner
Broken Cam Gears
Malfunctioning Cam Sensors
Incorrect Crank Gears(The I4 Has Like 40 Different Configurations For Whatever Reason)
Incorrect PCM Flash
Issues Within The PCM
PCM Wiring
Bad Diaphram Within The FPR
Issues Within The Fuel Pump
Dirty Fuel Filter
Dirty Fuel Lines
Pre-Cats/Poor Exhaust Flow

If the above gaskets/seals have not been changed, change them. Clean your MAF sensor, throttle body.
Change your PCV valve and probably that short hose as well.
Inspect the intake accordian tube for cracks. Inspect for vaccuum leaks.
Put in a good Fuel system cleaner: Red Line Synthetic Oil - Gasoline Fuel Additives - SI-1 Complete Fuel System Cleaner
Inspect wires. Re-set ECU after doing above.

Thanks for the reply, apologies on not including more information. 6 Cylinder, 3.0L engine. Appreciate the tips on what to change/replace. No gaskets or seals have been changed so will do that as well as work on the other things you recommended. I have looked for cracks wherever I can and have not seen any. Will also triple check those wires again.