Smoke on startup, oil on threads & ash buildup on left 3 spark plugs, using oil Help!

[DeadlySteve]

Hello all,

My 1994 explorer has started running rougher and rougher and using more oil.

When I first start it, it cranks for longer than usual and there will be a puff of blue smoke (It then doesn't smoke at all).

It uses about a quart of oil every 1000ish miles.

I just changed the spark plugs and the 3 on the driver's side all had oil on the threads and substantial ash build-up. The 3 on the right had just a tiny bit of ash but looked just fine.

I'm guessing that means its the valve seals? Could it be anything else? Can anyone point me in the direction of a step-by-step video on how to deal with repairing / diagnosing this? I'm a DIY guy, but I've never replaced valve seals, head gaskets, etc. before specifically.

Thank you so much!

 

[Anime]

Could be valve seals, could also be blow-by from worn piston rings, a blown head gasket, or even a cracked head.

Cracked/damaged stock heads are not uncommon, though they seem to happen more on the 90TM heads of the 91-92 and less on the 93TM heads of the 93-94's.

Best bet is probably going to be pulling the driver's side head and have it checked for damage, see what shape the gasket comes off it, and check the seals too.

You could always use a compressor or other method of keeping the valves in to pull the seals with the head still on if you wanted to do that first. You might have to just replace the seals with new ones and pull plugs again in a few hundred/thousand miles to see if there's oil on them again to be sure, unless the old seals are in obviously damaged condition and were the cause.

If there's no head damage, the gasket is fine, and the valve seals were ok, and the pistons have burt oil on them, it's probably going to be rings.

I'd say it's most likely a damaged head, maybe a blown head gasket if the engine ever overheated.

There are plenty of videos on youtube on pulling heads, replacing seals, and lots of photos on the common 4.0L OHV head crack locatons.

 

[DeadlySteve]

Damn... Yeah, it did overheat last year unfortunately. Going down the highway and started blowing antifreeze everywhere. Engine went over into the red. When I've poked around on the net though, most people seem to say that blue smoke at start up and oil consumption is probably bad valve seals which you didn't even mention. Is there a reason you think it isn't that problem? Thank you for the help!

 

[vq5speed]

You could try Engine Restore additive. Some people don't believe in it but what do you have to loose. My X started smoking a little at start up and take off from a light. They say it takes 300-500 miles to stop your engine from smoking. I've had it in now for about 350 miles it doesn't blow smoke on start ups any more. I still see a little smoke occasionally but they say it take 500 miles were you should see no more smoke. If your engine is to badly worn out it may not work but why not try it.

 

[Anime]

If it overheated into the red, it's 90-99% likely to be either a blown head gasket, or just a completely cracked head. That's just how the 4.0L OHV is. The stock heads on these were kind of weak and didn't have enough material, so they crack when overheated.

On lots of motors, especially at high mileage, a worn valve seal would be a common cause of oil consumption. That would be if the motor was never overheated, and assuming the engine had no major known design flaws that would lead you to suspect something else.

It's just well known that the heads on the 91-94 Explorers eventually crack, and a stuck thermostat with coolant going everywhere sounds like it would do the trick. I don't doubt the valve seals are worn too, but they might be a small percentage of that oil leak, the rest is likely from the head or gasket damage.

The good news is that new aftermarket heads are thicker and stronger, so they don't have the weakness of the stock heads. That doesn't mean they will withstand overheating, but they are more likely to just have a blown gasket than a busted head. The bad news is that new heads are a few hundred dollars.