I have an ongoing problem with my 92' Ford Ranger with 2.9 V6. Every 4 months or so for the last year, I have engine roughness, misfiring, and occasional loud rattle from engine. It's the same story. I pull out the #2 cylinder spark plug and find that the porcelain insulator is gone. I replace the plug and the symptoms almost completely disappear and the truck runs fine. Then in another 4 months, the symptoms come back, I replace the plug, and I'm ok for another 4 months or so.

All routine maintenance/replacement with fluids, filters, cap, rotor, plugs, spark plug wires, belts, battery, fuel injector cleaning, fuel pump is current. The mechanic did some diagnostic with his "scope". But all it did was lead him to the spark plug. It didn't tell him what was causing the spark plug to go bad.

By the way, the truck passed emissions inspection yesterday. It has 242,000 miles on it.

Can anybody narrow down this problem further? What other diagnostic should be done?

 

I would look at egr flow, as the absence of it in any cylinder would cause that a cylinder to run "hot" and that would eat the porcelain off of it. Another thing would be coolant entering the cylinder. A thing exhaust valve seat could possibly cause it, but not as likely as the other two.

 

If nothing else run the truck for 2 months and pull the plug. Check the back of a Chiltons for the deposit references, and go from there.

 

If coolant was entering the cylinder, wouldn't the oil have a "milky" appearance. I have done 3 oil changes and the oil looked normal.

Dave

 

No ifcoolantwas entering the oil system you would. If it enters thecylinder if will be burned out,IE white smoke and if enough you will get a sweet smell at the exhaust. EGRand other emmission issues will show on the pluds as well.

 

I changed the oil last week, and this is what I observed:

There was a little bit of green slime on the inside of the oil filler cap, and some steam came out. I assumed the green was coolant. I noticed coolant seemed to be disappearing too.

When I changed the oil, the drained oil looked normal.

I don't know, seems to me that I am in the early stages of a failing head gasket, or maybe a small crack in the cylinder head.

Don't know what to do yet. I wonder how long I can go before it gets bad. The current engine has 243,000 miles, so I would have to replace the engine....very expensive. It wouldn't make sense to repair an engine with this much mileage.

Is there a less severe problem that might cause the coolant to seep into the combustion chamber?

 

Daveranger,
If you have a cracked head or block that would require replacement. But a rebuild if you have thebasic skill and tools (maybe a freind to lend a hand mostly and knowledge sometimes....IE it 1am time to stopfor the night)to do most of your own work you could do a basic rebuild. Rent/Borrow the special items cherry picker etc.Pull the heads, clean carbon build off valvesand replace valve seals. Drop the crank (here is were you will spend money well worth it) and have the crank TURNED not polished, and install new properly oversized bearings. Use the spacer puddy for checking clearence upon install (take your time and be **** about this part being perfect). Hone the cylinders and install new rings. Your done, and in most cases for under $1000in parts and machining. Takes time have a place to work. And prior to instlling the motor, if any other items are in need replace them, IE water pump, oil pump etc.....and the drive it another 100k.......