Ford ignition problem (EDIS-6)

billr

wrench
Staff member
Joined
Mar 12, 2007
Messages
7,286
Points
63
Make
Ford
Model
F-150 2WD
Year
1999
Miles
169K
Engine
4.2L V-6 auto trans (4R70W)
This is wasted-spark, firing order is 1-4-2-5-3-6, so paired cylinders are 1-5, 4-3, and 2-6

The first code was P0303. Pulled #3 plug and took compression. Compression was 200+, plug was reasonably clean, but gap was about .100" Closed gap to .040 but P0303 came right back. Next we swapped #3 and 4 plug wires, at the coil. Lo and behold! Code now became P0304. that indicated to me that the coil was bad. Swapped the wires back a couple of times to ensure the P0303/304 "swap" was consistent

So, in goes a new coil and that resulted in P0302. Took that coil back, put in another new one, and now code is P352 (coil B bad)

First question: Which is coil "B"? I would think it would be the second one in the firing order (4-3), but that is not the way they are physically arranged. The coil at front of truck is 1-5 (A?), center is 2-6 (C?) and rear is 4-3 (B?). The physical layout seems kind of goofy, but it is a Ford...

Aside from the wonderment about which coil is B, anybody have any suggestions on WTH is going on here? Did we simply get two bad coil units in a row???

I should add, since the plug gaps are so badly worn they are all getting replaced; 1-2-3 already done. Likewise, one of the plug wires broke trying to get it off the plug, so those are also being renewed; 1-2-3 done
 

grcauto

Hero Member
Joined
May 29, 2014
Messages
906
Points
28
This is wasted-spark, firing order is 1-4-2-5-3-6, so paired cylinders are 1-5, 4-3, and 2-6

The first code was P0303. Pulled #3 plug and took compression. Compression was 200+, plug was reasonably clean, but gap was about .100" Closed gap to .040 but P0303 came right back.

Next we swapped #3 and 4 plug wires, at the coil. Lo and behold! Code now became P0304. that indicated to me that the coil was bad.

No. That screams bad wire not coil.

Swapped the wires back a couple of times to ensure the P0303/304 "swap" was consistent

So, in goes a new coil and that resulted in P0302. Took that coil back, put in another new one, and now code is P352 (coil B bad)

First question: Which is coil "B"? I would think it would be the second one in the firing order (4-3), but that is not the way they are physically arranged. The coil at front of truck is 1-5 (A?), center is 2-6 (C?) and rear is 4-3 (B?). The physical layout seems kind of goofy, but it is a Ford...

Aside from the wonderment about which coil is B, anybody have any suggestions on WTH is going on here? Did we simply get two bad coil units in a row???

I should add, since the plug gaps are so badly worn they are all getting replaced; 1-2-3 already done. Likewise, one of the plug wires broke trying to get it off the plug, so those are also being renewed; 1-2-3 done
 

billr

wrench
Staff member
Joined
Mar 12, 2007
Messages
7,286
Points
63
Did you miss that the wires were swapped at the coil? The "bad" #3 wire/plug suddenly became OK when going to the #4 coil tower; and likewise the "good" #4 wire/plug became bad going to the #3 coil tower. Nothing changed except what end of the coil secondary was firing each plug.

Plan is to check grounding of the coil/driver module and to swap back in the original, to see if the P0303 returns and can then be swapped to P0304. We need to get some consistency with these symptoms. All plugs and plug wires have now been replaced; probably were the originals from '99
 

billr

wrench
Staff member
Joined
Mar 12, 2007
Messages
7,286
Points
63
Put in yet another new coil module. This third one did the trick, no more codes and engine runs fine.
 
Top