Changed cap and rotor, now it runs rough and has a misfire under load.

[Nikkormat]

Alright this is throwing me for a loop. Yesterday I noticed a rough idle while we were out for memorial day with CFSJA.

So today I poked around and found the graphite electrode in the cap was worn away to almost nothing.

I got a replacement cap and rotor from Napa for a 1985 F350 and it all went in fine.

Now its running rough, and has a very noticeable misfire under load. Coasting down hill it is backfiring out the exhaust more than usual. It almost acts like it has way too little timing.

Yes the timing connection is plugged in.

Could the phasing of the cap have changed from the old one to the new one?

I have reset the ecu twice without change.

[jsinajeep]

Sound like you got two of the spark plug wires wrong

[Nikkormat]

I have confirmed the firing order. I'll check my base timing now that you got me thinking about it.

[Tatsadasayago]

Yeah, I'd look at the timing. I experienced this a bunch back in the day with Echelin GM HEI caps that somehow got indexed improperly. They would retard the base timing about 10 degrees and had me scratching my head for a bit.

[Nikkormat]

It's an echlin. Hopefully that's my problem.

[FSJ Guy]

As they say, timing is everything... :- )

[babywag]

What type of cap was on it before? Large TFI style and replaced with same?
Only ask because small cap marked #1 is in a different position than TFI marked #1.
You wouldn't be 1st to not notice immediately.

[Nikkormat]

Autozone cheapie big TFI to "fancy" (overpriced) Napa echlin TFI.

[Nikkormat]

To followup, the echlin cap retarded the timing by 7 degrees. My base timing with the TBI was set to 0 degrees so that definitely explains some weird behavior.