All of a sudden running on 4 cylinders??

Hey guys I went out to warm up my 73 cj5 258 1bbl this morning and it started fine and sounded like it was running fine. When I went out to leave for work it sounded like it was running on 5 cylinders and did the same to and from work. When I got home I unplugged the spark plug wires one at a time and found no difference in idle when I unplugged cylinders 4 and 5. I have pulled the plugs out and hooked them to the spark plug wires and held them close to metal and they both have spark.

Another idea I had was maybe the timing chain jumped so I checked the timing. It is still at 6btdc.

Then I thought maybe the intake is leaking and causing it to run so lean it wouldn't fire so I retorqued the bolts. A couple were loose especially the one by the fire wall but thats near cylinder 6. After torquing the bolts down I sprayed carb cleaner around the intake runners to cylinder 4 and 5 and it made no difference in idle.

Does anyone have any ideas what caused this to happen?? Could it be a blown head gasket??

Also I have a little bit of oil on the plug of cylinder 4 but none on the one from cylinder 5. I changed the spark plug to number four even though the old one was still sparking.

Please help me figure this out.

Thanks

 

Do a compression check, might hace a blown head gasket.
betwene 2 cylinders
Andrew

 

:iagree: Compression check, good pressure try 2 new plugs. I have seen them be ok laying on the block to check for spark. But when installed they would short out through the threads, no spark. They looked good too.

 

In addition to new plugs, I would pull the distributor cap, give it a close inspection, and wipe it out well. Voltage can jump around and do funny things with a defective cap.

You don't mention what type of ignition you are running, but I always use copper based anti seize on my plugs. Any FLAPS should have it, don't get the silver stuff, it will say copper on the package.

I have a DUI ignition, and that coil is capable of putting out something like 50,000 volts. I want to give the plugs every chance to ground properly so that each plug gets the full coil voltage when it should, instead of leaking and jumping around in the cap.

Another thought is to fire the thing up on a dark night (not under a streetlamp or some such, dark) and look for a light show from your plug wires. You shouldn't see one. If you do, time to replace the wires, too.

 

Dave,
Why do you preferr Copper rather than Silver anti seize???

 

Simple, hard to find a better conductor than copper. AFAIK, there is no "silver" in the non copper stuff.

 

Hey guys. I found out why it was running on 4 cylinders. When I was replacing the spark plug that I thought was oil fouled I somehow switched the spark plug wires for cylinder 4 and 5. I switched them back and now it runs like normal. The problem must have been that spark plug I replaced.

Since I already bought a compression tester I decided to do a comp test because of the oil getting in cylinder 4. Here is the results.

Cylinders
1 130
2 130
3 140
4 113
5 127
6 131

Since cylinder 4 was low I put a little bit of oil in cylinder 4 and it raised to 132. would this mean I have worn rings on this cylinder? Is this prob why I have some oil coming out of my oil dipstick or could it be something else?

Thanks

 

bump

 

Yep, rings are wearing out. Not real bad yet, but I would be saving my money and paying a little more attention to my oil level.

As for the dipstick issue, yes, blowby can cause your problem. However I'd make REAL sure that my PCV system is up to snuff and there are no oil leaks, vacuum leaks, misrouted or clogged hoses or PCV non op. All that stuff is cheap to get right, and can make a huge difference.

My motor used to be buried somewhere under an inch of grease, oil leaks, air cleaner full of oil, the whole bit. Time, patience, and not much money later, I'd eat my lunch off the motor. No leaks, dribbles, or mists. Air cleaner dry as a bone.

Replaced PCV valve, new grommets in the valve cover, replace all the rubber hoses, get them routed correctly, get the dipstick to seal properly (by bending the metal pieces that cause the friction fit in the tube enough to get the thing snug) new oil cap, replace the valve cover gasket, and a new oil drain plug with gasket, and wonder of wonders, a 34 year old motor that doesn't leak, spew, spray, or seep oil.

It's like magic, I tell ya!

If you get all that stuff right, with the readings you gave, you should just BURN oil a little, but it shouldn't escape, be pushed out, or wind up in your air cleaner.

But save your money for rings, the time is coming.

Just my experience...