5.0L Miss... the saga continues - Voltage Test Help | Ford Explorer Forums - Serious Explorations

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5.0L Miss... the saga continues - Voltage Test Help

Cali' Explorer

Well-Known Member
Joined
December 14, 2003
Messages
477
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City, State
Sacramento, CA
Year, Model & Trim Level
'97 XLT 5.0
Hey Guys-
Well, its been a long long while since I've posted on here. After the fiasco with the motor chewing itself, I've been trying to just be happy driving it around. But at 8 - 10 MPG, its starting to get expensive again price wise to run.

If you don't remember my initial symptons, they are primarily a lack of power. In addition, I get a missing situation above 4,000 RPM (and sometimes as early as 3500 RPM now). It pops and loses power until it shifts. If I'm not at near full throttle (IE: 65% or less throttle), there's no popping. Also, no popping in the lower RPM range, even under WOT.

The entire motor has been replaced in the last 1500 miles with a brand new long block. This means all new block, cylinders, lower intake, cylinder heads, etc. In addition, it came with brand new spark plugs (they don't seem to last terribly long with how its running).

The engine does not throw ANY codes whatsoever. All the readings from OBD-II seem to be well within spec. Everything seems happy, minus the popping/missing.

I used a spark analyzer today to see what was up there. Here's where the help comes in. I measured the Peak voltage (Max, "Average" and Min) as well as Burn Voltage and Burn time.

I noticed that between the drivers and passenger side of the motor, there is a difference of about 7 kV from the highest reading to the lowest reading. The average readings from highest to lowest are: 18.4, 17.9, 17.1, 16.3, 15.8, 11.6, 11.4, 10.6 (This also happens to go from front of engine to back, and then from drivers to passenger side).

I also measure Peak voltage Max and compared, between the highest and lowest Max Peak Voltage, there is a difference of almost 14 kV. Now, all the docs from the scanner say to use the "Seen" value on the scanner, not the "Max", but I'm not sure. Does anyone have any experience with this or any suggestions?

I also did tests under load vs. not under load, but since there wasn't someone to help me with it, I can only compare the Max and Min values of each at Load vs. No Load. Again, not sure if this is an appropriate way to check the voltage.

I did replace the original coils with Accel aftermarket units about 3 years ago because the resistance on the Originals were just a hair out of range, but I still have them and could toss them in. But, I'd like to go about solving this more diagnostically because, after spending $5300 on a new motor, I don't have extra money to throw around.
 






Seems stupid- but I assume you have newish plug wires?

I had a wire crack- just a hairline crack. Under load, it would pop and backfire, in normal driving, it ran OK. It finally threw a missfire code and I pulled the plug wire, flexed it around and found the crack.
 






Yes, new wires about a year ago. I've put about 3,000 miles on the new wires so far.

When I really noticed the actual missing at higher RPM's, my wires had gone bad. It got to the point where all of a sudden one day it started stalling and sputtering. Checked things in the dark and all sorts of arcing was going on. I replaced the spark plug wires and that went away, but the missing at higher RPM was still there.
 






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