Misfiring 4.0l with no check engine light?

[redriderdan7]

I have a 98 ranger 4.0 ohv engine. having some ignition issues. wont fire on cylinder 4 and is spotty on 5 and 6. There are no codes on the computer. None have ever popped up. Truck is not driveable. I have replaced the ignition col, cam sensor, crank sensor, computer, andevery other sensor this truck has. All cylinders have between 125 and 135 psi of compression. Please help. 3 wyotech mechanics and a dealership dont know what is wrong.

 

[97ranger19]

plugs mine was misfiring on number 4 and would shoot code for the others but the back resistor of the sparkplug had a crack thew it and chiped off with my fingernail replaced that and been running good ever since

 

[shane96ranger]

Yeah, like above.....mine has had a cylinder 4 misfire (common theme it looks like) three times now and it's been the plug every time.

I recently posted on this because it seemed weird to me that I keep losing that plug specifically. They told me at Autozone that I should try the Motorcraft finewires, so I changed it over. That was last week, and again today my truck seemed like it was chugging again. Rather than me reiterate what was said, here's a link if you're interested:

http://www.therangerstation.com/forums/showthread.php?t=99877

I was looking at some of the receipts from the the previous owner, and remembered he had someone "fog" the intake manifold and they found a leak in one of the front runners and the EGR valve. The EGR has been replaced, but I'm going to replace those gaskets when it gets warmer outside. This may be completely unrelated though.

Also, a misfire can be caused by a fuel injector. Have you looked into that?

 

[modelageek]

I have a 98 ranger 4.0 ohv engine. having some ignition issues. wont fire on cylinder 4 and is spotty on 5 and 6. There are no codes on the computer. None have ever popped up. Truck is not driveable. I have replaced the ignition col, cam sensor, crank sensor, computer, andevery other sensor this truck has. All cylinders have between 125 and 135 psi of compression. Please help. 3 wyotech mechanics and a dealership dont know what is wrong.

what you are saying is that when you pull the wire off of the #4 cylinder and test for spark you are getting NOthING as in NO spark and on 5 and 6 you are getting a weak spark......IS THIS CORRECT?.........If so. have you replaced the wires?

 

[modelageek]

you might want to start a new thread in the 4.0 engine forum. you will get more action from people familiar with this motor

 

[adsm08]

I'm with modelageek here. You have replaced everything but the two cheapest, and most common, points of failure in the ignition system. The plugs and wires.

This sounds like a case of bad wires to me.


Also, it is possible for a misfire to be noticeable when driving, but not severe enough to set a code.


Finally, my little sister, who can change a tire but needs supervision to change her oil, knows more about how to fix a car than 3 wyotech graduates.

 

[redriderdan7]

plugs and wires were the first step. done it twice since. it acts as though its not getting a signal at all from the cam or crank sensor, but my friend back probed both and both had god signal. i tried a timing light and two kinds of plug wire testers. no spark of no. 4 and weak/intermitent spark on 5 and 6.

 

[redriderdan7]

i tried that to. also checked the resistance of all sensor wire to make sure they dead ended at the computer to.

 

[Ranger44]

If you've replaced the PCM (which contains the EDIS ignition drivers), coil pack, crank sensor, plugs and wires.....your only options are wiring, and or a bad part from the box.

 

[adsm08]

Ok, do this:

Put your spark tester on, then swap all the wires to the tower on the other side of the coil. Re-run spark test. See if your results change.

 

[Ranger44]

Ok, do this:

Put your spark tester on, then swap all the wires to the tower on the other side of the coil. Re-run spark test. See if your results change.

Now that would be alright.