Spark issue

Joined
Apr 22, 2015
Messages
22
Points
1
Age
50
Make
Ford
Model
F-150
Year
2003
Miles
160,000
Engine
4.2
2003 Ford f-150 4.2l, 160,000 miles.

My main problem first is that on bank 1 side. Cylinders 1,2,3. Have a KV meter put on it then I get 4.5k to 6k volts on that side only. On the bank 2 side 4,5,6. Then get 17k on each of ignition wires or better. Have replaced coil pack. Ignition wires and plugs. Checked for grounds on engine ok. What could be my problem? Also do get the lean code but will post more info this. However could this be the cause? Have to go for now but will contact asap on this post.
 

billr

wrench
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Mar 12, 2007
Messages
6,879
Points
48
Are you reading these voltages with the engine running, with the plugs installed and firing? If so, first take compression readings. Compression pressure greatly affects the voltage it takes to cross the plug gap. At the same time that you take compression you could either swap the plugs from bank-to-bank after gapping them, or just replace them if there is any doubt of the condition. Have you checked resistance of the plug wires? That should be roughly 10K ohms/foot, but certainly they should all be about the same per foot.

Is this a wasted-spark system with three dual-tower coils? Maybe that spark tester doesn't work as well on the two different polarities of the tower/wires. Try swapping the wires at each coil and see if the results also magically swap from bank-to-bank.
 

NickD

wrench
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Aug 28, 2007
Messages
5,149
Points
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Since I was designing these things from distributors to distributorless, what a name, very curious as to what type of meter you are using for spark voltage. Essentially, a direct current flows through the primary winding that produces magnetic flux in the core. The greater the core size, the greater the number of joules for the spark. The only time high voltage is seen at the spark plug is when the current flow through the primary is stopped, and it must be stopped very quickly. The field collapses at a high rate, dv/dt to induce a voltage across the spark plug gap, in this voltage is only present for at most, about a microsecond.

One way to increase the spark gap voltage is to increase the gap, but since the voltage is greater, the current is much weaker and can be blown out by tuberulance in the cylinder. More important is to measure the current, need a darn good scope for this.
 
Joined
Apr 22, 2015
Messages
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1
Age
50
I do get a p0171 and p0174. The condition of the vehicle did run bad. I replaced the intake gaskets. Now the vehicle runs great now. But these codes keep comming up. The pcv is located in the throttle body. However, I do have a light rear main seal oil leak. Would this (main seal oil leak) affect my lean/rich condition or is it the spark issue? The rpms is a slight higher than normal. Will post how many rpm at operating temp when get a chance.
 

NickD

wrench
Joined
Aug 28, 2007
Messages
5,149
Points
48
That PVC in the TB is another weird EPA requirement. PVC is returning carbon that builds up everywhere on the intake circuit, especially the fuel injectors. Just cleaning the face of them off, fouls up the spray pattern.

Both left and right banks are running lean and lean translates to more combustion heat, warping exhaust valves.
 

billr

wrench
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Joined
Mar 12, 2007
Messages
6,879
Points
48
Can you do a compression test instead (or along with) of the leak-down? I find that compression is quicker/easier to do, and gives more reliable results.
 
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