Need Help with Missing Engine
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Joined: Jul 2009
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Need Help with Missing Engine
I have a 2002 F150 with a 4.2L 6cyl. I started running like crap, so I put new plugs, wires and coil on. No help. A compression test showed the number 2 cylinder was low. I pulled the heads and had a valve job done. I put it back together and it is missing. There is good spark coming out of the coil for cylinders 1/2/3. The spark for cylinders 4/5/6 is weak.I am not sure what to look at next.
Lead Driver
Joined: Sep 2006
Posts: 7,907
Likes: 143
4.2 ignition.
It is a waisted spark system not used on the v8 or v10 motors.
The cylinders are paired. Three coils for 6 cylinders.
Pairs are 1-5, 2-6, 3-4.
One plug get the positive side, it's mate gets the negative side for voltage. As you see the leading cylinder number on the passenger side is paired with a cylinder on the other side to keep mechanical balance during firing along with an internal balance to finish out the smoothing process.
Depending on how you tested spark, if by color it may mislead you but still be good.
.
Are you sure you have to correct fire order wired per cylinder to terminals on the coil pack. The coil terminals are numbered. #1 cylinder is front passenger side. Coil post numbering is 1,2,3 toward the back on it's passenger side. 4, 5, 6 on the other side.
Again there are three coils in the pack feeding 6 cylinders and need to be in the correct pairs.
Did you get any misfire codes?
Recheck your work.
Good luck.
It is a waisted spark system not used on the v8 or v10 motors.
The cylinders are paired. Three coils for 6 cylinders.
Pairs are 1-5, 2-6, 3-4.
One plug get the positive side, it's mate gets the negative side for voltage. As you see the leading cylinder number on the passenger side is paired with a cylinder on the other side to keep mechanical balance during firing along with an internal balance to finish out the smoothing process.
Depending on how you tested spark, if by color it may mislead you but still be good.
.
Are you sure you have to correct fire order wired per cylinder to terminals on the coil pack. The coil terminals are numbered. #1 cylinder is front passenger side. Coil post numbering is 1,2,3 toward the back on it's passenger side. 4, 5, 6 on the other side.
Again there are three coils in the pack feeding 6 cylinders and need to be in the correct pairs.
Did you get any misfire codes?
Recheck your work.
Good luck.
Mountain Pass
Joined: Apr 2017
Posts: 170
Likes: 9
Are you not getting any codes? Is the CEL on?
I had a miss a couple months ago that turned out to be a failed injector, but it tripped codes indicating a lean bank and real time analysis showed a faulty injector. When I tested the electrical resistance of the injectors, the bad one showed an open circuit while the rest were something like 22 ohms.
I had a miss a couple months ago that turned out to be a failed injector, but it tripped codes indicating a lean bank and real time analysis showed a faulty injector. When I tested the electrical resistance of the injectors, the bad one showed an open circuit while the rest were something like 22 ohms.
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