not firing in # 6

I have a 225 v6 its not firing well in number 6

compression 120

has spark and wires are on right (cap rotor, and plugs all new)

one thing to note the bolt of the rockers on 6 came loose i tored it down seamed to help but still not right

I get a miss at high speed also

i am kind of lost

 

How do you know it is number 6 cylinder ?

 

2 reason

1. pulled the spark plug wire not change to the motor
2. poor a small amount of water on the hear #6 stays wet a lot longer that #2

 

I made a rig so i could blow air in the cyclinder could not hear any leakage

did get enough PSI to turn the motor

 

You say the compression on that cyl is 120, but what is the compression on the rest of the engine???

Basically there are only three things that can cause a single cylinder to act up, and you have nailed the two that are the most probable.

Fuel is the other, and for a crab it is pretty hard to mess up the fuel distribution to a single cylinder-------worst offender is usually a vacuum leak at the intake port gasket, or a hose off a fitting very close to that cylinder.

My $$$ is on an ignition problem, second choice is a compression issue, bad valve, stuck valve, broken piston or ring etc.

Good luck....

 

I did not do the hole motor

#6 110
#4 90
#1 120

I guessing Ingition also

i have spark at the plug i pulled the plug out and grounded it it sparks

 

OK, here is an idea for you.

Switch both the plug, and the plug wire from the bad hole, to one that is good.

Now, go run it again, and see if the problem is still there, and if it is now moved to a different cyl, or is it still at #6.

If the problem moves, it is either the wire or the plug.

Your use of water on the exhaust is a good way to check for a dead or not full time firing cylinder.

A spark plug can fire just fine in the free air, but still misfire when it is under cylinder pressure.

Good luck.

 

Look very closely at your valve springs on #6. A broken valve spring may not show up on a compression test.

 

I did the spark plug and wire change it did not change anything


#6 still not running at 100%


I will pull the value cover as soon as i can

 

O.K., now you know the problem is NOT ignition related----------------that is unless it is in the distributor.

Have you popped off the cap, and taken a good look at the inside-----and the rotor??

As Corveeper says, could be a valve spring also.

 

I think the fact that you had a rocker arm problem on that cylinder is the clue. I'll bet there's a valvetrain problem, and the valve isn't opening properly.

 

Cap, Rotor, plugs, and wires are all new

and yes the they still look new

 

next step is to pull the rocker cover off and see what going on in there

Was hoping it would not have to come to this

 

Yep, that is why I was trying to get you to do the easiest, cheapest testing first.

Is this an engine with stud mounted rockers, or shaft mounted rockers??

 

So I pull the cover and nothing looks wrong

cranked it over all the value open and close

Nothing looks to be broken

double checked the compression and still 120 cooled

There is a vaccuum line for the tranny on #6

could it be leaking enough to cause this would it only effect the one cylinder ?


I am running out of ideas can you tell

 

Yep, I mentioned that earlier. See post 6.

Try plugging the line, and see if it helps.

This may be a line to a vacuum modulator, if it ruptures the diaphragm, it will let in a lot of air----or depending on how things are built, maybe some tranny fluid.

How did the plug look from that cyl when you took out the original set???

 

plugs looked normal

ok i will put eveything back together and block the vaccum line

hopefully that will work

 

good news and bad news

bad news first

good thing about parking jeep on a slant it does not leak bad thing is all the fuel run away from the pick up lol so i am kind of out of gas =)

Good News

before i ran out of gas everything seamed better but i ran out of gas just as i went to pull the plug wire to see lol

so you will most likely be hearing from me again soon

 

Thank you everyone for you help

Hopefully this will be my last post (still need to get gas )