Fox Misfires Under Hard Acceleration - Carburetor Experts Needed

[FastDriver]

That plug and the 2nd one on the bottom both look fouled to me. Could be a bad head gasket, poor control from the oil control ring, a valvetrain issue, or an very rich condition specific to that cylinder. Time to break out a compression gauge and check them. Take a close look at the wires. Incidentally, what is the heat range of those plugs? Gap looks big, but can't tell from a pic

 

[Demustangs]

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[Demustangs]

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[Demustangs]

Autolite i cleaned them still same results

What kind of plugs and what is you gap

 

[General karthief]

That bottom right (#1?) Plug looks suspect, white specks and deteriorating electrode is telling us something, check timing chain and balancer for accuracy, like said above new plugs and check wires.
What type of ignition system?

 

[General karthief]

Autolite i cleaned them still same results

What number autolite?

 

[Demustangs]

That bottom right (#1?) Plug looks suspect, white specks and deteriorating electrode is telling us something, check timing chain and balancer for accuracy, like said above new plugs and check wires.
What type of ignition system?

All replacement stock parts new but stock

 

[Demustangs]

That bottom right (#1?) Plug looks suspect, white specks and deteriorating electrode is telling us something, check timing chain and balancer for accuracy, like said above new plugs and check wires.
What type of ignition system?

Stock for a 89 I already replaced with new stock months back

 

[General karthief]

I need specifics, stock would be for efi, you have a carb

 

[Demustangs]

I need specifics, stock would be for efi, you have a carb

89 Crown Victoria distributor GT40 heads the cast iron ones e303 cam Autolite spark plugs Ford stock spark wires all of that is less than 6 months old 650 Holley double Pumper electric choke 1.6 roller rockers pedestal mounted stock fuel pump stock fuel filter I didn't replace those the filter in the pump I didn't replace those I have a fuel pressure regulator from Jegs down to 6 PSI for idle

 

[Demustangs]

Its a 89 crown vic block and bottom end all stock with a e303 cam cast gt40 heads dual valve spring upgrade dual plane intake 1.6 roller rockers 650 Holley DP stock 89 mustang fuel pump and filter which I haven't changed at all

 

[General karthief]

What is th part number on the spark plugs and are you running the efi ecu

 

[MustangIIMatt]

Wrong plugs for your application.

If you're running iron GT40 heads from an Explorer, try a set of NGK 3951 or Motorcraft SP-413.

Those platinum Autolites you're running are: 1. The wrong material, 2. The wrong reach, and 3. The 2nd worst brand of plug on the market.

 

[Demustangs]

At work don't know the number right off hand and yes efi ecu

 

[Demustangs]

Ok I'll give those plugs a tr

Wrong plugs for your application.

If you're running iron GT40 heads from an Explorer, try a set of NGK 3951 or Motorcraft SP-413.

Those platinum Autolites you're running are: 1. The wrong material, 2. The wrong reach, and 3. The 2nd worst brand of plug on the market.

I'll give those plugs a try thanks

 

[General karthief]

I'm not familiar with running a efi ecu and a carb, also that crown vic 5.0 has different pistons in it and lower compression, I had valve clearence issues with a crown vic 5.0 and an f cam with gt40p's.

 

[Demustangs]

Wrong plugs for your application.

If you're running iron GT40 heads from an Explorer, try a set of NGK 3951 or Motorcraft SP-413.

Those platinum Autolites you're running are: 1. The wrong material, 2. The wrong reach, and 3. The 2nd worst brand of plug on the market.

What gap do I gap the plugs so it's fine right the first time?

 

[Demustangs]

I'm not familiar with running a efi ecu and a carb, also that crown vic 5.0 has different pistons in it and lower compression, I had valve clearence issues with a crown vic 5.0 and an f cam with gt40p's.

The E cam works with lopo pistons like I said the car ran great for like 3 months straight no problems hard launches and everything just one day I stomped on it a little and it started backfiring and the plugs are oily and stuff cleaned plugs still pops under hard or WOT

 

[MustangIIMatt]

What gap do I gap the plugs so it's fine right the first time?

Factory gap in the orignal application is .054".

 

[jrichker]

You probably have 2 plugs that are not firing.