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Discussion Starter · #1 · (Edited)
I am hoping someone can help me figure this out...

I was driving the car home from a trifive meet in Reno, and the car all of a sudden started running rough when I came to a stoplight. When I got the car home, I checked the plug wires, and #6 and #7 were shorting to the headers. So I replaced the plug wires, and started down my journey of gremlins. (note, not the same cylinders which are missing)

I am having at least 2 cylinders miss (#2 and #8). With the car idling, I can pull these plug wires and nothing happens, if I pull others, the idle gets rough.

Triple checked the plug wire order.
Checked the spark plugs and the are firing with a good spark.
I have replaced the plugs.
I have replaced the plug wires.
I have replaced the cap & rotor.
I have replaced the coil.
I have run a compression test and all cylinders are showing 170lbs (+-2).
I have checked the springs, and none are rattling or feel loose.
I checked the rods on those two cylinders and they appear fine. When the valves are closed, I can spin them without binding.
While running the pressure check, I watched the valves, and they all seem to be moving the same amount.

The distributor is an MSD 8360.

Visually, everything seems to be working, there is no odd engine noise that would indicate a problem.

Thank you for any help.

Cj
 

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Just a thought.... Did you check to see if the valve lift was in spec. might have a flat cam. Other than that everything you have done should have fixed the problem. Hope you find it!!
 

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Maybe bad lifters, possibly collapsing at idle. They may be plugged up and not pumping up.....it just sounds like valve train to me as all the electrical has been checked out.
 

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Misfire

Hi CJ have you hooked up a vac guage? it will tell you if a bad valve or valves is your prob by a very quickly fluttering needle. #2 and 8 same side .....poss wires crimped into something and grnded causing misfire and no change when plug wire pulled. run at night and look for some kind of electric lightshow... nothing like a relaxin hobby...CHEERS TERRY
 

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Just a thought sometimes when the spark plug leads are pulled off the rubber boot doesn't allow the internal spark plug lead connection to wrap round the sparkplug.
 

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Just a thought sometimes when the spark plug leads are pulled off the rubber boot doesn't allow the internal spark plug lead connection to wrap round the sparkplug.
Yes, mine are so tight you really have to push HARD to get them to snap on.
 

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I have a spark plug wire testing device that I got through a friend who is a mechanic. It is a sight glass with a light inside. It has a wire on one end that you plug the spark plug wire onto and another wire on the other end that you slip onto the spark plug. When the engine is running if the spark plug wire is good you will see the light inside the sight glass flashing. I use it to test all my plug wires. Maybe you can find one and test your wires one by one.

Don
 

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Everything else good?

Remove the distributor cap and wash the inside of the cap thoroughly with mineral spirits. Wipe and let it dry. Check the rotor also while you're in there, make sure it's OK. Change the spark plugs on 2 and 8 again.

JMO :anim_25:
 

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Discussion Starter · #10 ·
I will get at it again after work and try the suggestions. I will let you know what I find. Hope I can find a vacuum gauge.
 

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Discussion Starter · #11 ·
Ok... been checking everything tonight I could. I have triple checked the valves, and they are working properly. Right now, I am thinking it might have something to do with the intake manifold gasket having a leak.

Because the intake gaskets are reasonably cheap, tomorrow I am going to pull the intake and replace the gaskets hoping to find some damage?
 

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if you have an intake leak you can often find it by spraying carb cleaner around the gasket area. With the engine running A leak will suck in the fluid and cause the idle to increase.

I use a small propane torch. I open the valve on the tank without lighting the gas. Then In a well vented area I pass the nozzle of the torch around te gasket area with the engine running. A leak will show when the itdle increases.

either method will show a leak and is less work then pulling the intake!

Don
 

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Discussion Starter · #13 ·
Update

Ok... changed the intake manifold gaskets, and the car is firing on all 8.

I am trying to figure out what is going on, but when I pulled the intake the gasket on the passenger side was bonded to the intake and came easily off the head. I'm not out of the woods yet, have to see how it is this weekend and see if it fails again.

Cj
 
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