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Discussion Starter #1
1996 taurus OHV 3.0. When climbing a mountain on the highway (70 mph) engine light flashes, and engine misses badly. Upon throttling back, or reaching the top, engine runs normally. ONLY happens under these conditions. Code generated is cyl 4 misfire. I have changed and or tested the injector, plug, wire, and coil.....all are fine. My friend who is a 35 year ford mechanic is stumped....swears it must be electrical. (????) Any thoughts ? Thanks in advance.
 

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1996 taurus OHV 3.0. When climbing a mountain on the highway (70 mph) engine light flashes, and engine misses badly. Upon throttling back, or reaching the top, engine runs normally. ONLY happens under these conditions. Code generated is cyl 4 misfire. I have changed and or tested the injector, plug, wire, and coil.....all are fine. My friend who is a 35 year ford mechanic is stumped....swears it must be electrical. (????) Any thoughts ? Thanks in advance.



Sure sounds electrical to me too. When you say 'changed or tested' can you tell us what was replaced vs tested? I think it's probably plug, wire, or coil that is failing. If the plugs and wires haven't been replaced in a long time they are probably overdue anyway.
 

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Discussion Starter #4 (Edited)
replaced the injector and plug. swapped wires, but the issue stayed on cylinder 4, so not the wire. put in brand new coil..... issue still there. So... apparently not electrical. Compression is good on cylinder 4 when testing, but no idea if losing compression under load.
 

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Initial coil fails will first start to appear on high loads. I had a 89 Blazer that did that. My mistake was a new AZ coil that did the same thing. After pulling out my hair a switch to a Napa coil solved the issue. Motorcraft or BWD coil from Advance would my next step if plug and wire is new as those coil packs are the only good replacement ones.
 

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Discussion Starter #9
Initial coil fails will first start to appear on high loads. I had a 89 Blazer that did that. My mistake was a new AZ coil that did the same thing. After pulling out my hair a switch to a Napa coil solved the issue. Motorcraft or BWD coil from Advance would my next step if plug and wire is new as those coil packs are the only good replacement ones.
i replaced with a brand new BWD....same issue continued. definitely not the coil.
 

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Discussion Starter #10
thanks. compression was in the 140-150 range....a bit less than the other cylinders, but not much. engine has 385k on it, so pretty good compression, all things considered.
 

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Fuel pressure under load check is next. I'm assuming you already have a new fuel filter in place before pressure test under load.
I would wiggle the engine harness also with it idling as motor moves under load could be a harness issue.
 
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