Mercury Mountaineer 4.0L 6-cyl engine developed zero compression

[pacem]

all of a sudden I got poor idle, it was impossible to idle, it would die. I pulled the codes, it had P0106 if I remember correctly. A quick search said it 's the MAP sensor on top of EGR. Swapped that and to no avail.
Got my mechanic involved, he on a hunch pulled compression readings and at least one cylinder, #2 had zero compression. The one next to it pulled good numbers. So it's basically a parts car. 190K miles. 2007 model year.
Is that normal for 4.0L engine? It never overheated although when I looked the coolant was about 3/4 of a gallon low.
What would cause cyl #2 to have zero compression?

 

[Shel_B]

I'd take a look inside that cylinder with a boroscope and probably the other cylinders as well.

 

[Lubener]

A burned valve and a coolant leak.

 

[atikovi]

Obviously something broke. Or maybe a valve hung open. I blown head gasket or burned valve would show some compression.

 

[vpr5703]

It's worth noting that the 4.0L Ford engines from this era were known for timing system issues. If the engine jumped time, there could be enough contact between the piston and valve to bend the valve stem. If the other cylinders are showing compression, I bet the contact (if this is what happened) is just slight enough to cause the valve not to seat properly.

 

[Junk]

The 4.0 sohc engines seemed to have valve spring issues as well, have seen a couple over the years. Only way to know more would be a leak down test and probably partial teardown to see what broke. It all comes down to how much it's worth to you to find out what's really wrong.

 

[JHZR2]

Replacement engine time?

 

[atikovi]

Replacement engine time?

A 190k mile 2007 Mountaineer with a bad engine is scrap. Not worth the hassle even for a $300 junk yard engine unless maybe the rest of the truck is mint and he did it himself. Next, the transmission could go any time.

 

[pacem]

A 190k mile 2007 Mountaineer with a bad engine is scrap. Not worth the hassle even for a $300 junk yard engine unless maybe the rest of the truck is mint and he did it himself. Next, the transmission could go any time.

I was under the impression the tranny has already been swapped by the PO. But it doesn't matter. Maybe I can sell it as a $1000 parts car. Lots of parts adding up to at least $1,000.

The interesting thing is, it never overheated, the gauges read normal, there is no obvious leak, or smoke, or exhaust anomalies.

The only symptom is terrible idle, it will not idle.

 

[someonesomewhere]

I was under the impression the tranny has already been swapped by the PO. But it doesn't matter. Maybe I can sell it as a $1000 parts car. Lots of parts adding up to at least $1,000.

The interesting thing is, it never overheated, the gauges read normal, there is no obvious leak, or smoke, or exhaust anomalies.

The only symptom is terrible idle, it will not idle.

You may get lucky and find someone that loves the platform and has a solid drivetrain sitting in a wrecked one who is looking for a new body/chassis.

If you have the space to let it sit for a month or so, may be worth listing as a whole vehicle. Never know!