99 ranger 155k 3.0 flex fuel. 304 is misfire in cyl number 4
I replaced the plugs and wires and checked the coil. the compression in cyl 2, 4, 5, 6 and got 80-90 psi so they are consistent but consistently bad right, it may be my compression tester.

The #4 plug was spotless after running 5 min, the #5 plug had some black on it allready. Its hard to tell but it seems I had fuel residue on the plugs on cyl 5 and 6 but none on 4?

Whats next pulling the intake to get to the injector?

 

Can you hear the #4 fuel injector "click" when the engine is running???? If not, is there B+ 12 volts to the #4 fuel injector electrical connector at KOEO???? If so, measure the #4 injectors resistance, it should Not be open circuit, but with resistance in the 12-16 ohms range. If all that checks out ok, maybe suspect a computer ground switching driver problem, or a ground wiring problem to the computer firewall connector.

 

ok I pulled the injector and tested with an ohm meter, #4 is open, as in no continuety #5 and #6 both are at about 14-15 ohms So I am guessing its bad. Does that mean the coil is burn out inside? any point to replacing them all or just the one?

 

OK, good trouble shooting on the #4 injector being open circuit. Yup it indicates an open circuit in that injectors coil, so replace it with a specified one, that Closely matches the other injectors resistance value, so they all closely match for load resistance. This keeps the fuel injectors circuit load in good balance, which it'll appreciate!!!!

 

Great slapped everything back together, and I have the exact same problem. I have spark, but apparently no fuel, what gives? I checked the resistance of the new injector before I put it in it was 15 ohms.

 

OK good feedback on the #4 fuel injector replacement & its resistance match.

Sounds like you had more than one problem. When your helper cranks the engine with the starter, can you hear the fuel injectors "click" as the computer driver ground switches them????

 

thanks for the help, hopefully I can work on it some more tonight, I guess I should mention it has the 1401 code too but it always has that one....

 

Depending on how the injector burnt out, it may have taken out the corresponding injector driver transistor in the ECU.

If the injector shorted out first, it would send a ton of current to the injector driver, and solid-state electronics almost always fail by going short-circuit. So now the injector driver is shorted out, and keeps flowing power until it burns completely out or the injector goes open circuit.

All the injectors get constant +12v, the computer fires them by grounding them. You'll want to verify that the injector plug is getting +12v on one of the pins. Then they have these things called "noid lights" that plug right into the injector plug. You start the engine, and if the light is flashing, then the computer is firing the injector properly. If the light stays on steady, then the driver in the ECU is shorted and will need replacement. If the light doesn't come on, then it could either indicate a wiring fault between the plug and the computer, or the driver in the ECU is completely burnt out. If you have a normal test light, you can do the same thing by hooking it to the positive battery terminal, then touching it against the injector plug pin that doesn't have +12v.

 

P1401 = DPFE sensor high voltage, so after you get the no start problem fixed, have a look at the DPFE sensor itself, its electrical connector & interconnecting vacuum hoses. The computer uses the difference between the intake & exhaust manafold pressures to figure out how much EGR feedback the engine gets.

 

ok more fun and games
I get the +12 at the injector
I get a flashing idiot light on the neg with the engine cranking
I can hear the injector clicking with a mechanics stethascope
when I stick my latex glove covered finger at the spark plug hole I get 5 times the gas on cyl #5 as compared to cyl #4
neg ground flashing seems consistent between cyl 4 and 1 but thats really hard to judge.

So I guess I am on too:
ecm bad having the wrong pulse timing
clog in fuel line (unlikely since number 4 is the first on the feed for that bank)
new bwd injector being bad.
what say you sages?

 

so I swapped the #4 and #1 (I am learning if the fuel injector was bad at least I wouldn't have to remove the intake )

and now it runs just fine, I don't know why. well I did have a big vaccum hose disconnected the first time around the one going to the FPR and I didn't clear the codes so maybe I thought it was just the same problem? but it didn't pull any new codes.

anyway after I swapped the injectors and put all the vacumn hoses on it correctly it sounded good and I cleared the codes and drove it for awhile no problems.

I am concluding it was just a bad injector.

Thanks for your help

 

BTW I bought the torque app for my smartphone $5 and a bluetooth diagnostic plug (no wires )$25. And I have to say it is pretty darn slick. it pulls the code and will display the meaning per manufacturer and will link to common troubleshooting for the code. It also does realtime monitoring, things like rpm, throttle position, temp, vaccumn and a couple other things. it will also calculate your 0-60 1/8 mile and 1/4 mile and HP I am not sure how accurate it is but it gave me 80 hp and a 20 second 1/4 mile.

 

After we make a repair, we're supposed to clear the trouble code so that the computer knows the repair has been made, that way it clears any corrupt things its learned & stored in KAM, so the computer can begin to relearn things like its cold & warm idle, begin to rebuild the corrupt fuel trim tables it built with the defective injector, idle correctly when an engine load is applied, like the A/C turning on, or when we turn a heavy electrical load on, ect.

Seeing as how the old injector was open circuit, that cyl bank was running lean, so the computer had gone to a max rich squirt time for that injector bank & because you didn't clear the code to tell it that a repair was made, it began to operate the new injector at max rich squirt time.

With the FPR vacuum line disconnected, fuel pressure was corrupt & fuel trim from the vacuum leak also had the computer Really confused about what to do for fuel trim, all a vicious circle for it to try to quickly figure out what was going on & what to do about it.

SO, all that said, the new injector was probably just fine, it was the repair Tech that got all excited about finding the problem & forgot to complete the repair lol. Anyway, good to hear all now seems well & your on the road again!!!!

If your having any driveability problems, go through the cold & warm idle relearn proceedure, a forum search will turn up multiple links for it.

Some thoughts for consideration. Good feedback on your trouble shoot & repair.

 

Woops, this was to have been in the reps reply for your repair!!!!