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2002 ford ranger 3.0 misfire

Had a misfire in cylinder 1 so I put new plugs and wires. Still misfired. Changed fuel injector. Still misfired. Changed ignition coil and misfire on cylinder 1 is gone now cylinder 2 and 3 are misfiring. I double checked wires and they are properly installed. Any advice?

Double check the plug wires locations on the coils.

You don’t say…
Would you say the miss occurs mainly above 3,000 RPM?
Is the “Check Engine Light” on?

A 2005 Ford service bulletin that covers 2002-2003 Ranger, Taurus, and Sable models with the 3.0L engine and a miss with no DTCs (trouble codes) could be caused by a faulty Camshaft Synchronizer Assembly.

Checked Plug wires, will check again, cant hurt. Had codes read 2 days ago went home checked electrical connector to the ignition coil and plug wires. check engine light came on while i drove to work. Coworker said possible bad Ignition Module. was mostly curious because misfire on 1 cleared up and now on 2+3.

What Were The Specific Codes?
Please Give Us All The Symptoms And Clues You’ve Got.

Had codes read 2 days ago. Made sure wires were connected properly. Reset codes. Check engine light popped yesterday on the way to work. Just had codes read again, now only cyl 3 is misfire. codes are p0303 and p0172. i do plan on going out and checking #3 plug wire and resetting codes again. Will drive to work tomorrow and see if CEL pops again. Thanks for the help.

If the cam sensor is wonky it will tell the wrong coils to fire at the wrong time. The ecu fires whichever the sensor tells it to fire so if it screws up…you can get this.

What I would do is try another coil…I know I know…you replaced it… But I feel there is room for part suspect here…esp if it fixed the original misfiring cylinder and then it moved.

Its the cam sensor or the new coil pack. Would love to see what happens if you re-replaced that coil pack. Sounds silly…I know…but you would cry if you have seen the number of new part failures I have seen… I know i feel like crying sometimes.


Can an ECU fire a plug out of time @Blackbird? The only cylinder that is specifically identified is #1 on all the vehicles that I am familiar with and that includes Ford 3.0 V-6s

Once #1 cylinder is identified the ECU fires the plugs and injectors in the programmed firing order. I didn’t work on many Hondas though. And come to think of it I never had to diagnose a Honda missfire.

Swap whatever you can in the ignition system – spark plugs, wires, coils – between 1 and 3. If the problem follows the swap, you know you are getting to the bottom of it.

Edit: If you think the problem is timing, put a timing light on those cylinders, aim it at the timing wheel, and see if you notice anything weird going on. You might need to put some white marks on the timing wheel b/c 3 probably won’t line up with the 0 degree area.

A faulty cam sensor can’t cause a single cylinder misfire on that engine. The ignition system doesn’t work that way.

I would triple-check the plug wire routing and double check all the other work you did making sure everything is hooked up properly, and checking to see if a vacuum line somewhere didn’t fall off or something like that.

Like Rod Knox asked in his question… Can a faulty cam sensor fire a coil pack out of time… The answer is yes as its timing is dependent upon cam chain stretch usually. However ASEmaster is also correct stating that it cannot cause a single cyl misfire…but…when you mis your ignition window…and you are a spark plug in a cylinder. The delay or offset time in firing one plug or group of plugs will appear as a single cylinder misfire if it is timed just right…the ecu basically reports on just one of them… . Its a cascade effect essentially.

Now in a coil over plug system where everyone has their own coil…you will receive a much more accurate report card. When you fire them in groups you can get wonky report cards.

I think this engine still uses the wasted spark technique…firing plugs in groups of two. On many 4 cylinders this is the case…you will see 1 and 3… and 2 and 4 fire simultaneously which is why it is called wasted spark. 99 Audi A6 2.8 V6’s do this and those coil packs are like socks…you basically need to change them daily…Those coil packs fail like no ones business. My buddy keeps a spare in the trunk on an otherwise troublefree car. LOL… In that Audi example…you would never recieve just one misfire report…always grouped in twos. Depending upon the complexity of the ecu software or code…will dictate what kind of report accuracy it can reveal.

In this engine…with its single block coil pack…firing 2 at a time…how can it be super accurate when it knows it didnt fire one set of plugs? Or at least thats how Im thinking about it. This vehicle doesnt have the sensors or complexity to single out just one cylinder…so it reports as best it can

I will need to lookup what method this engine uses to trigger coil firing… Usually its an electronic sensor bolted into where the Ole Distributor used to be…this being on engines that were alive in the distributor days and have been updated over the yrs to more modern methods. Never know what you will get in the ignition department…especially when an engine is in production a long time.


Rod Knox…think about what would happen if the cam chain stretched so far that the cam is lagging behind and the number 1 cyl was no longer at TDC…and then the ecu just calculates the rest of its 360 rotation to fire the others…who also may not be cam phased properly at the moment of ignition.

Its a cascade of crap after that. I think you are correct in your assessment of this system on this engine. Its not very complex…more complex is sometimes nice…like coil over plug.