My car is a 5.3 V12 1988. On acceleration, I get a misfire. But once it reaches the target revs, the misfire disappears. Eg. if l'm at 1,000 pm and accelerates to say
3,000 pm, while getting there, I get a misfire. Once at 3,000 pm and I keep the revs consistently there is no misfire. Could it be ignition coil related or fuel filter/ pump related?

 

Welcome to the Forums.

Please do your thing in the New Members Area while we sort this simple beast.

The list goes:

How old are the spark plugs, AND< are they gapped at 0.025"?

How old are the 13 HT leads??, average life is 5 years.

Is the misfire noticed at Idle/?

It may be an Injector, rare down here, but you are up there. They fire in 4 batches of 3
1,3,5A
2,4,6A
1,3,5B
2,4,6B
Injector loom, the snake looking thing in the bottom of the V are failing now due to age.

How old are the dizzy cap and rotor, average life is 10 years.

Coils, fuel filter, fuel pump, ECU, Amp,etc ALL affect the WHOLE system, NOT one cylinder.

My bet would be plugs and leads.

 

If it's the plugs are the leads, the misfire wouldn't disappear right. Because there is no misfire when the car idles or when the revs are kept stable.

 

Maybe.

The V12 is not an easy engine to detect a misfire when not under load, and I have many hundreds of hours with these beasts, I am NOT perfect by any means.

The facts are the facts.

If the list I have given has an answer of "I dunno", then until they are sorted quietly and methodically, a lot of tail chasing will be done.

 

Under acceleration load the ignition system is doing far more work than at a steady cruise, and your ignition system sounds like it is breaking down under load. If you want a reliable car, do all the following, say I!: If they have not been done, then as Grant said renew the:

• plugs (gapped to 25 thou);
• the HT leads;
• the dizzy cap and rotor;
• the coils
• clean the resistor pack connector
• assuming a Lucas igniton car (?) lubricate the advance retard mechanism and make sure it snaps back properly when you turn the rotor against the spring
• check that the dizzy vac capsule is working (highly unlikely if not renewed recently), if not renew it

This is 100% necessary preventative maintenance for a reliable car. If the misfire persists thereafter, renew the amplifier.
It is also a good plan to rewire the ignition12v feed to the coil by taking the white 12V feed to the coil and using that to trigger a relay which takes its 12v load side direct from the bulkhead 12v post. A fused relay is a good idea in this case but use a 20 amp fuse.