1992 3.1L Missing #6

[corbetts_auto]

Here is one to scratch your heads over....I have a 1992 Isuzu Rodeo...it has the 3.1L just like the same year S-10s....you can hear the miss and if you pull the plug wire off the #6 plug there is no change...pulling the wires off of any other plug will change the idle.

It has a bad miss on #6. Below is a list of what has been done


new plugs, wires, cap, rotor
FI injection flush (the good pressurized can stuff)
removed valve cover and check the tightness of the rocker arms...they felt a little tight, so we backed them off a little to be sure the valves were closing all the way
Compression is 115 - 120 on all cylinders
swaped wires to be sure the #6 wire was good.
swaped plugs to be sure #6 had a good plug..
removed, cleaned and tested EGR valve


The #6 has fuel, spark and compression...why is it missing...what am I overlooking.

[71350ss]

Did you check the injector ? Also pull the wire connecter off the inj. and install a noid lite to make sure the wiring is OK to the injector.

[corbetts_auto]

It has a throttle body, so I can see both injectors firing...Thanks for the thought..

[Philip]

If the TBI was the culprit 3 cylinders would be missing. It has to be related to the #6 only. What does the plug look like? Is it real clean like a lean condition? If could be an intake leak bad enough to rob the power from that cylinder.
Did any codes come up?
When you had the valve cover off to did you start the engine and look at the lift on the #6 valves as compared to #2 or #4?

[corbetts_auto]

...When you had the valve cover off to did you start the engine and look at the lift on the #6 valves as compared to #2 or #4?

We checked the intake bolts and them seemed fine....of course there still could be a leak...May just buy a set of gaskets and remove it to eliminate that.

It may be hard to believe but the plug actually looks fine...a nice honey brown color.

We didn't run it with the cover off (too messy), but we did watch the rocker arms. They felt a little tight so we loosened them up just a touch. Just to be sure the valves were seating...

I guess I'll try the replacing the intake gasket....I'm sure when I find the problem it will be simple :clonk: