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Fuel Injector Replacement

O'Rattlecan

Redneck Prognosticator
26,687
797
Belton, MO
Hi guys,

My 1994 has a chronic misfire. It's fouled 2 plugs (same cylinder, only it's done it twice.) It's cylinder 4 (passenger back).

The motor has about 5k miles on it since I rebuilt it a few years ago. I replaced the distributor cap, distributor rotor, spark plug wires, and ignition coil. I am ready to do the plug again, but wonder if it's probably the fuel.

If and when I pull the spark plug, I guess I'll determine whether it's running rich or lean.

Help me think through this. If it's black and soiled, is it running rich? And then if it's white and has carbon, is it running lean?

Are both scenarios likely to be the injector since it's the only cylinder that's fouling?

Ryan
 

LEB Ben

Arrogant A-hole At-Large
34,919
1,124
outside your house
It IS possible for both scenarios to arise from a bad injector. Just did all of them on my Lincoln not long ago. Middle two cylinders were throwing codes on opposite sides. Front was clogged, creating a lean situation (white to light tan plug). Rear had a nick in the nozzle and from what I can tell, letting too much fuel in the cylinder...causing it to run too rich (totally black plug). Both cylinders threw injector codes, both cleared up after replacement.
 

O'Rattlecan

Redneck Prognosticator
26,687
797
Belton, MO
Cool, that's good feedback. I was thinking about doing testing to verify it's only one cylinder, but the last time I tested (and replaced the plug) it was only one.

Having said that, I looked around, and a set of 8 injectors isn't much more than buying a single replacement. Since the intake plenum has to come out and the fuel rail has to come off, I may as well do them all. The only other scenario is that the wire loom is defective and causing it not to operate. But I'm praying that's not the issue because then I'll have to remove everything all over again.

Ryan
 

john112deere

caffeine junkie
Staff member
10,807
405
central Vermont
Is it fouling with fuel, or oil?
 

O'Rattlecan

Redneck Prognosticator
26,687
797
Belton, MO
I'm going to pull the plug shortly, but the last 2 times it fouled, it seemed fuel. If it's not obvious, I may share with you guys and see what you think.

Ryan
 
'94 would have batch fire EFI, so if it was a wiring problem causing a rich fuel condition, you would see it on 4 cylinders. Same if it was a lean condition. An intake leak could also cause a lean condition on one cylinder. With it being #4 cyl, that is a possibility. Really need to see if it is rich (black) or lean (white) fouling when you pull the plug to inspect.
 

dustybumpers

don't play well w others
There was also a problem with the PVC hose being in the #4 runner of the plenum, fouling out the plug starting in 1993

Drill and tap a new hole near the center of the plenum, and plug that hole

I remember there being a TSB, but that has probably timed out
 

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