Ford 4.0 v6 engine cylinder 5 carboned

[willys54wagon]

Have torn apart a 1993 ford explorer engine 4.0. Only cylinder 5 is carboned up. Hard carbon about .5 inch thick by valve seats on the head. rest of cylinders are cleaned and good.

General symptoms before taking apart were: misfiring, low gas mileage, spark plug fould, no codes, good compression. lots of oil by valves

MIleage on engine unknown becaseu it is not orig. This could be a new year engine and one source said that a new engine in a 93 could cause problems.

mechanic diagnosed as cracked ring but cylinder walls look good. Is it possible the rings are stuck? and how would we know. top of piston looks silver like it is brand new, other pistons have normal wear.

Are there any know problems with this engine? Have a chance to buy a used engine with 71,000 miles for $550. What are the options you would suggest.

 

[wavinwayne]

I would suggest a water de-carbon treatment, performed S L O W L Y, & with extreme caution. That should clean the carbon out.

 

[Matt_S]

Lots of oil on the valves, but none on the piston crown and no scoring on the cylinder wall would lead me to suspect the valve seals before anything else. I wouldn't necessarily junk the engine over it, though.

 

[willys54wagon]

Local machine shop thought it is stuck rings. This is a friends auto. Engine already apart. Would it work to just clean the rings for that piston and put it together again? Or is it better just to go get the $550 engine and be done with it?

Why would just one piston get stuck rings?

 

[javacontour]

You've already done a lot of the work. If everything measures out, why not hone the cylinders and install new rings as well as re-work the heads.

At least this way, you know the condition of the engine. You have no idea about that $550 engine. I would go with knowing it was re-freshed properly if spending my money.

T

 

[Hirev]

I'm not understanding this? If the engine is torn apart than just looking at the piston in the ring area should tell you if the ring is stuck or broken. You can have a broken ring and still have cylinder walls look fine. If the valve guide and or valve seal is bad than you should be able to tell if the motor has been taken apart (head striped).