I have a 2000 Explorer 4.0 SOHC that I'm having a persistent problem of cylinder 3 misfire. I've changed plugs with Motorcraft plugs set to the proper gap, put on new wires and have checked the resistance across the ignition module, both primary and secondary without change. I doubt that the problem could be the ignition control module as only cylinder 3 is affected. I have Auto Enginuity that I use to read the codes, attempt a repair and then clear the codes only to have P0303 appear again. Obviously the engine stumbles and has poor acceleration. Can anyone offer and other suggestions???

 

Are you up to the challenge of swapping fuel injectors between cylinders? I'd also suggest you swap the spark plug from cylinder #3 with a different cylinder, and preferably from a different cylinder than where you moved the injector to. Then see if the misfire remains on cylinder #3, follows the injector, or follows the spark plug. If it remains on cylinder #3 then you need to figure out if that wire is getting spark or if the compression is low. You could also check the injector wiring to make sure the injector is getting pulse.

-Rod

 

compare injector ohms to the other ones

 

Measuring the resistance of the injectors would be a simple starting point, but could also prove inconclusive. The measurement can indicate a faulty injector, but a static DC resistance measurement will not identify a stuck injector or one that is partially or completely plugged. The injector coil could still be fine, but yet no fuel will flow through it.

-Rod

 

Thanks Guys,
I'll swap the plug (unfortunately it's the most difficult to get to). Then I'll check the resistance on that injector before I attempt to move it to another cylinder. If after swapping the plug and checking the injector I still get #3 misfire I'll pull the injector and move it. It's kind of making sense that it may be the injector as the misfire occurs under load as in accelerating up a hill but subsides when I level off speed. At first I thought that I had a fuel related problem as it felt as though I was "running away from my fuel supply" but I'm holding 65 psi fuel pressure which rules out the pump or filter. On second thought I may swap out the injector first if it's easier to get to. This problem began several months ago with an occasional "hiccup" that never set a code but within the past 2 weeks has gotten much worse. Is there a reliable cleaning procedure for an injector or is replacement the best option? I'll kep you posted.. Thanks again!

 

I have one of these in my tool box Fuel Injector Cleaner | Mechanics Tools Warehouse, has worked like a charm on several vehicles... Philip

EDIT http://www.youtube.com/watch?v=bKGI9N_yWd0

or less sophisticate way. http://www.youtube.com/watch?v=VFJlT...eature=related

 

Sorry to butt in on your thread but I am having the exact same problem. My 06 FX4 5.4 started hiccuping a few months ago, i was at the dealership for something else and they told me it was my #6 fuel injector. I decided not to fool with it then b/c they wanted like 800 bucks to fix it. I am a girl but a girl that thought that was ridiculous. This weekend it started misfiring really bad whenever I accelerated or tried to idle. The check engine light finally came on, so I am taking it to my buddys house tonight to put it on the machine and confirm that its the #6 injector. If the machine confirms its the #6 I am just going to fix it myself. .
My friend told me I needed to do them all if I was going to replace one, but I dont feel like dishing out the extra money if I dont have to.
So my question is, will I get the best results out of my engine if I replace them all? and how long can I get away with not fixing them with the truck driving as badly as it is?

 

In my opinion replacing all injectors for only one bad one is not something i would do, they go out too far and in between to replace them all for one bad one ,besides you really dont feel the difference changing good injectors

 

I agree, I would only replace the one that is proven to be bad, not all of them for one bad one.

With that said, the scan tool is not likely to identify a bad fuel injector. It is more likely to give you a code of P0306 which still just tells you the PCM has identified a consistent misfire on cylinder #6. You'll still need to determine if the misfire is spark, air/fuel ratio, or compression related.

-Rod

 

For what's it's worth, my mom's Dodge Grand Caravan had a misfire under certain loads. Most often she would notice it when backing up the hill of her driveway. It turned out to be caused by a flat spot on the intake valve. After checking spark and replacing the fuel injector, Dad and I performed a cylinder leak down test and found air hissing through the intake. He replaced the valve (which interestingly was less expensive from the dealer than from the parts houses) and now all is well.

-Rod

 

sorry to jump in this thread, but I'm having the same problem. my check engine light has been on for years and codes were for oxygen sensors on catalytic converters. replaced plugs, wires, fuel filter this summer. started hiccups when driving. took to mechanic who ran B-12 thru injectors (I'm assuming--he just mentioned he ran B-12 thru) and after that was when rough idle and acceleration started and it smelled horribly of exhaust. he suggested I replace cats-after replacing my catalytic converters my truck is still runnin rough and another mechanic told me my rings are bad at 4 and 6 which will cost me $4,995. supposedly he did a compression test. I do not have and have never had any smoke coming from my exhaust. Just extremely rough running, no power, and hiccups or coughs when accelerating. Any suggestions or thoughts would be greatly appreciated as the cost of ring replacement is WAY MORE than my vehicle is worth. 98 Ford Explorer 4.0

 

What are your current fault codes?

 

A cylinder decarb will cause the thick exhaust until it either evaporates out completely or the carbon burns out. It could take a week before the thick exhaust completely goes away after a decarb, but it should get less intense over the course of that week. It depends on how carboned up the cylinders/valves are. I would certainly goes for a second opinion before dumping the truck or dumping that kind of money in to this one.

-Rod

 

codes are P0304 and P0306.

 

I would start the misfire process of elimination, easiest to hardest , first change 4 and six plugs or swap with others,if no luck, ohm injectors and compare to others, if out of range ,replace ,no luck swap with others to see if code moves ,no luck, check connectors for injectors , no luck, see if injectors are pulsing their is a light tool for this,if ok move to wires swap ,the lengths are close, next coil , all these can cause a misfire code good luck