Misfire at constant speed : 302 EFI

[jakester888]

Consistent misfire on the 302 EFI at steady speed. No problems under acceleration. Research suggests to check the TFI module. I have an aftermarket MSD distributor with the black TFI module mounted on. Do I need the grey TFI?

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[frankeeski]

Sounds like a bad wire to me (spark plug wire).

[Jeff Kleiner]

Sounds like a bad wire to me (spark plug wire).

Or incorrect firing order.

Jeff

[frankeeski]

Or incorrect firing order.

Jeff
Nah, That would show up while accelerating.

[Ram4x4sprt]

Make sure to separate wires 7 and 8 in looms as fords will sometimes cross fire

[jakester888]

Make sure to separate wires 7 and 8 in looms as fords will sometimes cross fire

I'll check 7&8.

I'm pretty sure I need to swap the black for a grey TFI, however... Since the motor is from a 93 LX and all the references I find online seem to suggest grey with that year.

[skullandbones]

Jakester,

I did the same thing. I was putting my distributor back together after cleaning it up and had more than one set of stuff for the different engines (used the black one, accidentally). It works but just not good. I had a 92 system so I found several references to the grey TFI. Hope that is the only issue.
WEK.

[jakester888]

Problem solved: it was not a TFI issue. I simply added a grounding strap from the frame to the starter/engine. This solved 3 problems: misfire under constant speed, no startup when hot and one solenoid click - no start. Yes!

42593

[CraigS]

Good job. Over 30 or so years as a tech, I can't tell you how many problems have been caused by bad grounds. When looking closely at modern engines the big ground cables are obvious. A longer look will show small ground wires in many places especially around the intake.

[6t8dart]

I agree, I always run a ground strap between the block and frame...now I have to remember to do so on my MKIV.