running rich on 4 cyl?

[Mephisto]

without going into a drawn out diatribe here's what's happening...

the truck runs like its not firing on all cylinders or the timing is off...

there's no power and you can hear the exhaust popping at idle.

i pulled the spark plugs on the passenger side and all 3 are black. On the drivers side 1 and 3 look fine and #5 is black.

so i know i'm running rich, but how could i be running rich on only 4 cylinders and the other 2 are fine?

the only thing i can think of is that i was installing my fuel psi gauge before this started happening. I removed the shrader valve and put on the adapter hose from RPM. There's no fuel leaks and i didn't crack the rail or anything like that.

the fuel psi is at 45

i messed with the timing a few degrees in each direction with no improvement.

i'm at a loss as to what could be causing this...

I have a hard time believing that 4 plug wires could go bad all at once.

can't really 'search' this without getting a phonebook of threads that are all unrelated.

 

[berzerker]

Re: running rich on 4 cyl?

how do you know it's only firing on four cylinders ?

do a check on the exhaust manifold temps with a spray bottle of water by running engine and spray each cylinder exhaust port with the water .. the water will steam or sizzle off if the said cylinder is firing correctly .

the hotter the temp on the manifold ports the better... it then show a good cylinder firing - contribution...


you'll then be able to narrow down what cyliders are firing or not.

then look into ignition , broken valve train components , or injector issues .



good luck

 

[Mephisto]

Re: running rich on 4 cyl?

i'm sure all 6 cylinders are firing... but I'll try the spray bottle anyway just to be sure.

i haven't driven the truck more than 5 miles since this started happening and 2, 4, 5, and 6 spark plugs are covered in black soot like the cylinders are just getting flooded and can't burn all the fuel that's being dumped in there.

i don't think there could be an issue with the computer that would cause that on only 4 cylinders... wouldn't it do it to all of them?

If it's an injector issue it's odd that it would happen to 4 of them all at the exact same time.

don't think it could be the coil, since 2 cyl seem to be working fine.

and much like the injectors, i don't think i could arc 4 plug wires all at the same time.

i'll pull the cap and see if anything is going on in there.

thanks for the tips berzerker

 

[Norm]

Re: running rich on 4 cyl?

Intake leak?

 

[Don W.]

Re: running rich on 4 cyl?

IIRC 1,3,5 fire off one ECM circuit and 2,4,6 fire off the other, The injectore are "hot" all the time. The ECM provides the ground so some wiring checking might help. I actually had a simular issue before my teardown. I was rich on 2,4,6 and normal on 1,3,5. Motor ran fine. I ended up putting one heat range hotter plug in 2,4,6. My motor did not miss like you're describing. You could easily swap a couple plug wires to check them. Timing will prolly not fix this IMHO but check the inside of the cap and also make sure all wires are inserted all the way. Same with the plugs. How old are the wires? I did have some issues a year ago which were cleared by replacing the ign wires. In your case could it be just coincidence?

All I can think of, HTH

 

[Mephisto]

Re: running rich on 4 cyl?

ahhh so maybe this is the problem.... i pulled the chip out and popped the blue cover off and turns out it's not a stock chip but the ATR shitbull chip...

anyone got a stock chip to sell/borrow???