5vz problem...

[Mossyrocks]

I changed the plugs, started it up, backfired and runs on 5 cylinders... Dont know which one yet, hard to say. Pulled each on the driver side and couldnt tell a difference no matter which one we pulled.

put the old plugs back in and same thing. Pulled each plug one at a time on the driver side and checked for spark, they all sparked. Dont know the cylinder number but backside on the driverside was black when we pulled it. The new one, the entire end was black.

Im at a loss.

[Good Times]

By black are you saying the bottom end of the spark plug that's white is now all black too?

Check your air/fuel mixture as it might be too rich. Not sure why it's only on one cylinder but a black spark plug usually means you're running rich. Also you might have a problem w/ your plug lines or quite possibly the wrong plugs? Then again if this happened to your old ones I'd say it's either the a/f ratio or a bad plug line.

[Seanz0rz]

might be a stuck fuel injector, how does the exhaust smell (along the lines of running rich)

[Tankota]

I changed the plugs, started it up, backfired and runs on 5 cylinders...




:shake: Guys, let's not overthink this just yet.


Ok, I'm calling a plug wire in the wrong whole. The symptoms you described are classic mixed up wire syndrome.
You need to determine firing order on the dizzy cap and then confirm correct routing.

[Seanz0rz]

no distributor on a 5vz-fe...

[MTL_4runner]

I changed the plugs, started it up, backfired and runs on 5 cylinders... Dont know which one yet, hard to say. Pulled each on the driver side and couldnt tell a difference no matter which one we pulled.

put the old plugs back in and same thing. Pulled each plug one at a time on the driver side and checked for spark, they all sparked. Dont know the cylinder number but backside on the driverside was black when we pulled it. The new one, the entire end was black.

Im at a loss.


Few questions.....

1) So the new #6 plug was black and the others were all the normal color? Then when you reinstalled the old plugs the same #6 fouled again? Was the original #6 plug black when you took it out? Pics of the old and new plugs in order of the cyclinders they came from would go a long way towards sorting this out and what diagnosis could be made to fix it.

2) Did you change or move anything besides the spark plugs? Change wires, other engine work, etc?


Possibile culprits:

Spark plug (possible cracked insulator but not likely given what you did already, get 1 new plug to be sure)
Plug Wire (possibly damaged or swapped by accident, check wires with a DMM)
Ignitor (swap with another ignitor and see if the problem moves to another cylinder)
Injector (possibly stuck injector)
Mechanical issue (check for low compression)

[Tankota]

no distributor on a 5vz-fe...


Really, hehe. Ok yes I am old school. Is it coil on plug or something, or coil near plug?

Another common problem that comes up during spark plug changes is damaging the wires while removing them. MTL pretty much covered all your options there.

[MTL_4runner]

no distributor on a 5vz-fe...


Is it coil on plug or something......


Yep, it is.....100% computer controlled.

[corax]

if you could scan it for codes and find out which cylinder is misfiring, we could go from there (p0301=cyl 1 misfire, p0302=cyl 2 misfire, etc)

the simple dirty test would be to find which cyl it is (by code, most chain parts stores will do a simple scan for free and tell you the code) then start swapping components off that cyl to other holes - coil to one cyl, injector to another, etc. - take notes as to where each part went. If the misifre moves to a different cylinder, whichever component got moved to that cylinder must be bad, right?

[Mossyrocks]

Its fixed... dont ask me how, just know that it is.

however, its running extremely rich. it was before as well though so I dunno.

Ill just run it til it pops and put an LCE pro short block in it. hehe

[corax]

however, its running extremely rich. it was before as well though so I dunno.



Make sure you don't have any leaks in the exhaust near the O2 sensors. If there is a leak, it can draw in air between exhaust pulses and trick the O2's into thinking it's running lean (extra oxygen in the exhaust = lean engine), thus making it dump more fuel. Even if the leak is a foot or two past the O2 sensor this can happen.

[MTL_4runner]

An exhaust leak is definately a possibility for running rich.
Probably something you'll want to hook up an OBD diagnostic for.