New Blue (for those that remember), 90 MEFI upgrade, AOD. Last weekend while towing boat from stg to water, she started BAD valve rattling under any load, only WOT alleviated it.

So I figured, hey this sounds like a chevy with EST when the module heads south. Mebbe I lost my module/timing advance.

1) I was unaware the TFI can fail THIS way, I thought they failed with zero spark, not bad spark?

So I figured ok, next trip to the lake (I leave the truck down there) I will swap out ign module and check timing (I used the chisel method to set the timing).

However, when I last worked on her, I moved the TFI off the motor and used a bad TFI in the jumper/piggyback configuration (I got the wiring diagram from here) to send PIP and get back the spark signal

2) the foil wrapped PIP line, was of course bad so I went to home depot and got 2 conductor shielded wire, and used both wires in the shield to keep resistance low since the distance is now 4ft (not sure how critical distance was, I dont have an ohm spec) but assuming I didnt shield enuf (I think the last 6 inches are open) where can I get the shielding tape? I wonder if the 2 lines used are causing a little spark echo?

And yes I will be checking cap/rotor (perhaps 3K miles old - accel components) and plugs (AP24's? 25's? whatever the ford size is)

Any ideas? I will be doing this in a field (my electrical tools travel well)

 

You can use foil tape available at most hardware stores. Peel back some of the rubber insulation to allow the foil tape to come into contact with the existing shield.

Not too sure what 2 conductor shield wire you purchased, but you could have induced a problem if the wires at not of the twisted pair variety.

I have not had an ICM fail with the symptoms you are having, they usually fail as no spark when warm. But with the mods you made, anything is possible.

 

Note that you can only ground the shield at one end, not both.
If you ground a both ends it will not work.

 

IIRC I used the ground wire ford provided and simply wrapped that around the shield. why not both ends tho? Im curious about that.

 

If you ground the shield at both ends you can introduce ground loops.