Can't edit the title. It's cylinder #5. Drivers side middle cylinder. Front passenger-most wire on the coil.

My 2001 Ranger 4.0 has recently developed a misfire on cylinder #5 - It has came and went a few times for hours or days at a time, and I drove it to work and back (40 miles total) for two days with no misfires. Then it came back again.

I've changed the coil pack, plugs, plug wires, Motorcraft crankshaft sensor. The fuel injector on #2 is functioning. Additionally, I know the injector is still supplying fuel because the resonator starts to smoke as it loads down with fuel.

Holding the pedal to the floor while cranking it doesn't try to fire, so no leaking injectors.

The computer connector is dry and free of corrosion.

The MAF is clean and the idle drops and almost dies if I unplug it.

The only codes I've had were related to the cylinder #2 misfire, and the truck has throw a code for the evap system for years, which should just disable the EGR.

I am NOT driving the truck in the meantime.

Any ideas?

 

I would do a compression test just to take that off the table
Because if it is a compression issue you will be chasing your tail for a long long time

Spark, at the right time
Fuel, mixed with air
Compression

That's really all there is to it for a cylinder to fire, lol, simple as that and as complicated as that
Take any one away and misfire

You seemed to have covered spark and fuel pretty well, so.......................................compressi on remains, and if its more of a steady misfire now then should be easier to detect

You can swap spark plug wires around at the coil pack
3 4
2 6
1 5
to
4 3
6 2
5 1

see if misfire moves to #1

 

I'm not against doing the compression test, and it had been thought of, but what baffles me is the misfire going away for several days and then coming right back again. More than once. That made me think it was ignition related. Or electrical connections.

Or EGR possibly? I'm not sure how bad a misfire can get when faulty EGR parts are involved.. Never been down that road just yet..

Thanks for the suggestions Ron. you've always been a huge help on the forums.

 

I have a misfire also but it's not throwing a code. Did a block test block has no leaks. I'm thinking one of the push rods are screwed.

 

The valves rotate each time they open, an exhaust valve can stick and not rotate so gets a hot spot which causes the start of a burnt valve, misfires, then starts to rotate again, no misfire, then repeat, this would get steadily worst over time, i.e. more misfires as time goes by, as the effected cylinder's compression rides that psi line between firing and misfiring
So in the beginning a burnt exhaust valve will be intermittent issue

Its certainly possible its spark or fuel related, the compression test is done because it is a black and white test, eliminates compression as an issue or confirms it as an issue
Spark and fuel are not so black and white

You can use the old time timing lights on a spark plug wire to watch the spark pulse to see if its "skipping a beat" on a specific cylinder
So don't get rid of these, and if you can find one at a garage sale get it, lol, they still have a use

 

Today's testing after buying two new tools

Compression on the missing cylinder: 180lbs
Fuel pressure at the rail is 58lbs after cycling the ignition, and it drops to about 55lbs and holds there after about 3 to 5 minutes.

Moved the spark plug from cylinder #5 to cylinder #6 and the misfire stayed at cylinder #5 so it's not a bad plug.
Swapped the plug wires on #5 and #6 and the misfire stayed at cylinder #5 so it's not a bad wire.
Swapped the plug wires on the #5 and #1 coil towers and the misfire stayed at #5

Tested the resistance between the top two pins on the DPFE as shown in this video: I probed the connector pins and I'm getting 4.8volts at the pins. He shows 5 volts on his meter.
Though I didn't try the vacuum test like he does on one of the hoses while checking the voltage. Yet.

Only thing left to check is the #5 injector I suppose. They do have 210,000 miles on them.. Though I have often ran Lucas injector cleaner in the fuel, as well as Heat from time to time in the winter. That still doesn't explain why the resonator is loading up with fuel and running extremely hot. The #5 spark plug comes out mostly dry looking though, so I'm thinking the injector is bad.

 

Swapped the coil pack wires 5 and 1 is what you meant right?

What were some other cylinders compression numbers?
Point of a compression test is to compare multiple cylinders tested on the same day with the same equipment, not a specific number
If other cylinders tested as 170 or 190 then there would be a fault in 5

And on a 4.0l SOHC you really want to do BOTH banks as one bank's cam can get out of time with the other causing higher or lower compression numbers on that bank
So just do all 6, all spark plugs out for the test

Also do a sanity test for the cam sensor and computer by disconnecting spark plug wire #2 or #3
Firing order is 1 4 2 5 3 6
Misfire codes are detected by lack of added power to crank/cam spin, so micro-second timing differences
2 and 3 surround 5, and as good as computers are they can goof
so you could have an issue with 2 or 3 not 5 at all, so you are focusing on the wrong cylinder

You should get 2 misfire codes with either #2 or #3 disconnected

 

Yes, coil towers #5 and #1. I edited that info.

I didn't check any other cylinders because 180lbs is within specs for the 4.0 sohc from the research I've done, and in-line with numerous other Ranger and Explorer owners past results. No other cylinder on this engine is going to test any/much higher. It has over 210,000 miles.

When disconnecting the #5 plug wire at the coil (while running) there is a spark that jumps to the plug wire but the engine sound and rpm doesn't change, so the offending cylinder is indeed #5

I had two misfire codes before, but I can't remember them.

I'll try to disconnect #2 or #3 while #5 is misfiring and see if it throws another code, but it didn't the other day when pulling wires from the coil one at a time.

I also plan to pull the cam sensor and see how much metallic material is stuck to it.

 

The reason you test all the cylinder is because of false readings
What if you tested another cylinder and it was 250psi, so a pressure gauge issue
So yes the 180psi is spec but what if the pressure gauge is not, lol

 

I know that much, but I have zero reason to not trust the gauge.

I will pull some more numbers.

I'm still leaning towards injector or cam sensor, but I'm not a professional by any means. I've just owned nothing but Rangers and Bronco II's for over 30 years.

It very well could be a sloppy chain/no guide material left on the drivers side as well.. Throwing the timing off a minute amount. It's always had a timing chain rattle at around 2300 to 3000rpm. Though I baby it because of that.

 

Well, my personal junkyard here on the farm came in handy once again. This old 2002 ex cab gave it's life so that other Rangers like her can live.. I bought it purely for parts with a supposedly blow up engine. I've never tried to turn it over. This truck has paid for itself 5 times by now, and I still have a manual trans and transfer case in it should I want to convert to manual in my 2001 Ranger. So far I've used several small electronic parts, the coil, a couple plug wires to get me by, the rear frame section and the rear frame "horns" below the rear of the cab to weld on to my truck/then bolting on the rear frame clip with grade 8 hardware, the rear window, bed bolts, etc.


My 2002 parts Ranger, amongst it's fallen brethren.


I pulled the cam sensor and it was nice and clean for having 210,000+ miles on it.

I checked compression on a couple other cylinders and came up with 185 to 190lbs on each. Those numbers compared to cylinder #5 are probably within the accuracy variance of the gauge itself.

I bought a $20 NOID light set and was getting pulses to the injector, so I removed it and replaced it from one that I pulled from the passenger side of the parts truck.

Turns out I had a faulty fuel injector on the #5 cylinder after all.

So if anyone has a misfire that comes and goes, then comes back permanently, and new plugs, wires, coil, and crank sensor doesn't solve it, look to your injectors. Especially if the misfire stays at one cylinder when you move plugs and then plug wires.

The down side is now my oil pressure gauge doesn't work. I must've accidentally unplugged something or bent a pin in the large connector by the coil when I reconnected it. Further investigation is needed on that, but overall she's running stronger than she has in a few years. I dumped in a full bottle of HEAT and a full bottle of Berrymans fuel additive. Then treated her to a full tank of premium at $5 a gallon.

I also (hopefully) sealed up a water leak at the top passenger corner of the rear window and reattached the cab corner trim on top with the same sealer. Currently drying out under the vinyl floor with a small fan and the flooring pulled up. Hopefully she stays nice and dry now. She's getting worked hard tomorrow falling a huge cherry tree, so....

Thanks for the assistance Ron!

 

Good work