"Programbo" <programbo5@[EMAIL PROTECTED]
> wrote in message
news:93f2e598-60c1-4e93-9765-21c51a8286c9@[EMAIL PROTECTED]
> My 1994 Jeep Cherokee (Inline 6 4.0) started running really rough last
> week as if one of the cylinders was missing. I changed all the plugs
> and wires and cap/rotor and that fixed nothing. I was thinking maybe
> an injector wasn`t working and turned the Jeep on and unplugged each
> injector one at a time. Unplugging 4 of them made the engine start to
> die off right away but the #2 and #3 injectors didn`t seem to change
> anything when I unplugged them. So I figured those injectors were dead
> and replaced them. No change again. Still running really rough. (I
> know it was stupid wasting money but I really needed to try and get it
> running as I had a trip down the highway I had to take on the
> weekend.) I finally got tired of messing with it and took it to a
> repair shop and the guy there called and told me, "There`s no
> compression in those two cylinders." To make a long story short I just
> told him to leave it alone and I`d come pick it up. But today I was
> off work and went out to mess with it and I unplugged and removed the
> 2 spark plugs for those 2 cylinders (They were black with soot) and
> when I fired the Jeep up there was a lot of air being pushed out of
> the plug holes as the engine stroked. So I guess my question is: Isn`t
> that compression? I`m trying to eliminate possible simple fixes before
> junking this thing. Thanks for any input.
So, with no plugs in it, the piston will push air. When the plug is
replaced, the rings/valves seal to create compression. I am willing to bet
there is still compression but very low.
Do you have a compression tester?
Put a teaspoon of motor oil in the plug hole and check compression again.
If
it goes up it is rings, I believe. Stays the same, if it is valves. Did
mechanic do this test?
The soot is basically unburnt gases and blow by gathering on plug. I
believe
that would be normal with a bad cylinder.
Could also be head gasket in which case you probably would have oil in
coolant as seen in radiator.
Could also be blown between cylinders which may explain the two being
dead.
Mechanic should be able to narrow it down and recommend fix.
Let us know what gives!
Warren
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