03 Explorer 4.0 multiple cylinder misfire

Asked by Feb 18, 2017 at 09:46 AM about the 2003 Ford Explorer XLT V6 4WD

Question type: Maintenance & Repair

A few months back I bought a 2003 explorer 4.0 4X4 with
170K miles. It ran perfect until recently it developed an
occasional misfire at highway speeds that gradually got
worse over a couple weeks, to the point where it wouldn't
accelerate over 75-80 mph because it would misfire so
bad. It would still idle good but it'd only do it when trying
to pass or on a steep incline, then one day after it
misfiring nearly the entire 50 mile commute to work, i go
to start it after my shift and it will barely idle and has no
response when I gave it gas. I attempted to drive it and
it's top speed was about 10 mph and would die shortly
after taking off. At this point, the check engine light comes
on for the very first time since this all started and starts
blinking so I had no choice but to park it. I get a ride home
and come back the next day with a code scanner and get
four codes: P0300 - random/ multiple cylinder misfire,
P0301, P0302, P0303 - misfire in cylinders 1,2, and 3. I
changed the coil without any luck then had it hauled home
on a trailer. At this point it stalled about 15 times (no
exaggeration) before it was backed off the trailer. I later
changed the fuel filter and I'm still having this problem. It
hardly won't even fire now. It'll start if you try long enough
and but most the time it only cranks. White smoke comes
out of the exhaust and it smells like unburned gas.  I'm
waiting on new plugs and wires to be delivered , although
I doubt that's the problem, I'll just go ahead and change
them to rule it out. My question is, is there anything that
commonly goes bad on explorers that would cause it to
misfire on 3 cylinders? And what can cause misfires only
on one side of the engine? Why does it have no response
to throttle? I need help diagnosing this problem and would
greatly appreciate any suggestions of what to do or where
the start. I don't want to spend a lot of money throwing
parts at it because it's not even worth $2k. Thanks a lot in
advance!

6 Answers

98,345

A lot of things can cause this, leaking injectors, bad fuel pressure regulator, incorrect sensor readings, faulty computer and sensor grounds, shorted ECM and the list goes on. Do you have access to a live data scanner, as that maybe the only way you are going to find the actual problem if it is engine management related.

50,735

I wonder if the spark plugs have ever been replaced?

73,035

P0300 FORD - Random Misfire Detected...Possible causes; Faulty spark plug (s), Faulty ignition coil (s), Clogged or faulty fuel injector (s), Intake air leak, Fuel injectors harness is open or shorted, Fuel Injectors circuit poor electrical connection, Ignition coils harness is open or shorted, Ignition coils circuit poor electrical connection, Insufficient cylinders compression, Incorrect fuel pressure...The P0300 code means that a cylinder(s) is misfiring or is randomly misfiring. Start by checking for intake leaks, intake gaskets are common caused of multi-cylinder misfiring. If no leak are found the next step is to replace the spark plugs. If the problem persist more tests needs to be done to diagnose problem.

I have a scanner, but my only problem is, it won't even start now so I can't see live data.

73,035

Check this out.... https://youtu.be/7qPc-fl29LI?list=UUnNYOHy9KCVneECxJy8XU6A

98,345

The engine does not need to be running to view live data, I've found bad sensor readings and wiring problems without the engine running.

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