My '94 Explorer runs like it dropped a cylinder, rough idle, no power and smokes at open throttle. Its a v-6. I pulled the plugs and found all the plugs on the drivers side were fine but the ones on the other side were fouled and the middle one's tip was completely burned off/melted. I replaced and re-gapped all the plugs and it started up fine and seemed to run ok. The next day it was running bad like before. Any ideas what is wrong?

 

There are a # of possible causes.
1)bad injector to cylinder that had bad plug
2)Bad intake manifold gaskets
3)burned piston due to running lean (clogged injectors)
4)burned valves
Do a compression test on the cylinder that had the bad pulg
let us know what you find

Rich



Ford Trucks Built Tough!
not with rocks
Watch out "X" Mayor of Truckville

 

Thanks, I'll check that. What should normal compression be?

 

The actual compression value isn't that important.. What is more important is that they are within 10% of each other..

On our 1992 we had recessed valves and cracked heads. On the cylinders the the compression problems we only had 40psi or so.. On the cylinders without the problems we had 160psi.. (not bad for more than 236k miles)


With the new heads installed we now have 160psi on all cylinders..

BTW.. according to my book 110psi on the lowest cylinder is the limit. If any cylinder is < 110psi it is time to get some work done. Just like if the is more than a 10% difference between the highest and lowest cylinder..

btw.. you can check to see if the problem is rings or something higher by squirting a little oil in the cylinder before you take the compression test. If the compression is higher with the oil the rings are bad.. If it doesn't come up the problem is at the head gasket or higher (which means take the heads off and see what the problem is)

~Mark

 

I checked compression and all but nr 2 cylinder were good, 120-140 psi. Nr 2 cyl was practically zero and the plug was oil fouled. My feeling is that the pistons rings are gone, what do you think?

 

Looks like your either having some work done or your doing it yourself
Did you squirt some oil in there and see if it changes the reading.
Really not needed, you have to pull the head on that side to see whats going on.

Rich





Ford Trucks Built Tough!
not with rocks
Watch out "X" Mayor of Truckville

 

[updated:LAST EDITED ON 15-Mar-02 AT 06:40&nbsp;PM (EST)]Sounds like time for some work..

your kinda in a gray area.. If you had good compression all the way around (140psi or so) I'd say just replace the heads IF that is actually the problem.. but having only 120psi isn't exactly good (it is within spec, but low on the chart)..

if you crack the head you can get oil into the cylinder and these heads will eventually crack (ours did at 236k miles or so)..

if the heads aren't cracked between the valves you can get some money for your core.. If they are cracked you must pay the $200 core charge PLUS the $150 for rebuilt heads (that is what we paid last summer)..

If you drop a little oil in the cylinder and do the compression test again and the compression comes up, you have bad rings.. (go for the rebuild).. If it doesn't you may be able to get away with only doing the heads.. but you will eventually need a rebuild anyway.. If you have the time/money, go for it now..

~Mark