Misfire #3 - Ranger-Forums - The Ultimate Ford Ranger Resource


4.0L OHV & SOHC V6 Tech General discussion of 4.0L OHV and SOHC V6 Ford Ranger engines.

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  #1  
Old 05-02-2016
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Misfire #3

Did a plugs and wire tune up October 15.
Now running with miss . Pewter says 3 misfire.
Think its injector.
How much top of engine has to come apart to replace?
I can't even see the injector to test.
Any thoughts ?
Thanks Keith
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  #2  
Old 05-02-2016
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what size engine?
what code are you getting?
How many miles on the truck and or engine.
Have you checked the compression and basics out before blaming the injector?
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Old 05-02-2016
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No code just misfire #3 on obde 2 scan.
97 4l V6
160,000
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Old 05-03-2016
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Recheck coil pack wires and wires at spark plug

Coil pack
3 4
2 6
1 5
Front

The 5 6 4 side always gets me, either at the coil end or spark plug end, I reverse 5/6

And pull #3 spark plug and change it with #1, I have gotten bad spark plug out of the box, if misfire moves to #1 get another spark plug.

If you think it is an injector then disable the coil pack, unplug its wire connector.

Crank the engine a couple of times
Pull out #1 and #3 spark plugs, both should be equally wet with fuel, you need #1 to compare.

If #3 is dry then remove wire on injector and check injector with OHM meter, should be between 11-16ohms
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Old 05-09-2016
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misfire #3

Did old fashioned spark check 3 is good at coil.
Did a screwdriver ear test injector clicking.
Could be clogged.
Next is compression test.
Thanks for all feedback.
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  #6  
Old 08-16-2016
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With a stethoscope you can easily hear if an injector is physically pulsing.
The injector could still possibly be blocked, but I don't know how common this is.
So this test is only to confirm electrical and physical operation of the injector.
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Old 08-17-2016
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col good, injector good. oil on plug.
compression good.
I assume it is valve seal
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Old 08-17-2016
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Is it the only spark plug with signs of oil?

Valve guide seals can be changed without removing the heads.
You remove all the spark plugs, so you can rotate engine easily
Remove valve covers, use rags to plug ALL the oil drains in each head
Rotate engine manually until the piston of the cylinder you want to work on is at Top Dead Center(TDC)
Now rotate engine backwards about 1/4 of a turn
Feed some flexible rope into the spark plug hole on that cylinder, so it coils up inside
Now rotate the engine back towards TDC for that cylinder, it will stop as the rope presses against the head and valves
Valves will now be held in place so you can remove the springs and replace the seals.
I put a bungy cord on the socket wrench on the crank to hold pressure on piston pushing the rope up, just seems to keep valve stems from moving when removing and installing the springs

repeat for all cylinders

The reason for the rags in the oil drains is because you WILL drop a spring keeper, lol, and if hole is not plugged it will fall down that hole.

And when getting the new valve guide seals it isn't a bad idea to get a couple of extra keepers, they can go MIA if one pops out and fly's away.
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Old 08-21-2016
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Thanks for response. RonD
I cant get to computer every day to respond.
Couldn't I just pressurize cylinder with compressed air and get same result?
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Old 08-21-2016
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Yes, many do use air compressors for this, cylinder still needs to be on TDC.

I don't trust my luck so won't use compressed air to hold valves closed, down side is too far down for me, lol.
If I should lose air pressure for any reason, i.e. broken hose or fitting I would have to pull that head.
With the rope method I just feel more comfortable.

Same amount of setup time for each cylinder so one is not easier than the other, just prefer the physical contact than the air only.
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Old 08-21-2016
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Quote:
Originally Posted by audioguy View Post
Thanks for response. RonD
I cant get to computer every day to respond.
Couldn't I just pressurize cylinder with compressed air and get same result?
If you use compressed air, make sure it's in gear so the air can't accidently rotate the engine.
I've had that happen.
Also, have the piston on it's highest point when doing this just in case you do loose your air.
If that happens, the piston will catch the valve and keep it from falling right inside the bore.
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