OK so starting from the beginning I have an 04 F1 50 Fx4 with 239,000 miles , with the obvious ticking sound they seem to all develop .. so my buddies dad was listening to it and heard a vacuum leak up by the passenger firewall, which he plugged back in and said it was to my four-wheel-drive and that my wheels have been locked in but not my transfer case .. well I said that I hadn't noticed any mileage difference or difference in the truck. so after this I didn't know if it was just in my head or not but it seemed like my truck was laboring harder going down the road . three days later after he did this my truck shows a flashing engine light which is the third and fourth cylinder misfire ring and the engine is shaking all over . now I'm told the engine has no compression and is basically toast. when he plugged in that vacuum back in did he engage my wheels actually then ? also now that apparently the motor is gone am i better off just buying a replacement motor ?

 

No compression doesn't tell us much. Zero or low compression and in what cylinders?

If the valve timing is off that could affect compression. Maybe investigate the problems a little more before throwing mucho dinero at it.

 

When I do compression tests I write down each cylinder's readings and compare them to manufacture specifications

 

Regardless of the compression on which cylinder, after 239,000 miles you have to know that the truck is tired. Unless you've spent a bunch of money on it to keep it pristine, you'll be throwing money into this truck like it was a money pit. The transmission is tired, as is the bearings, transfer case, brakes, cooling system, alternator,power steering, etc. If the truck is pristine with the exception of the engine, you need to know that to do it right will cost more than just a long block. You'll want a new water pump, hoses, etc items to make sure the new engine doesn't kill itself due to a faulty high mileage part.

 

yeah i was gonna plan on changing a few things along with the engine that would basically "be due" to fail, but i have otherwise kept up with the maintenance well, honestly im more interested in knowing what happened when he plugged that vacuum leak back in. my buddy said i should have cycled my 4x4 in and out to clear the system. think i should just scrap/salvage the thing?

 

Get another compression test done and get the numbers for each cylinder.

 

I doubt hooking the vacuum line did anything to it. It's probably just coincidence.At 239,000 miles, it was time for something to come apart. The only one that's going to know if the truck is salvage or repairable is you. You're probably going to throw 4 grand at a truck that's only worth about $6800. around here. If you have any other parts that crater afterwards, you're out even more money. As I remember correctly, the 2004 FX4 came with a fixed set of driveshafts that the entire drive shaft assembly has to be replaced. You can't just replace U Joints. They have to be tired. But only you can make the decision to throw the money at this one or look for another one. Might even consider a junkyard engine, replace the bad one, get it running decent and sell it. Then look for another truck with a lot lower miles.

 

Oh S@%*it ! I just got a FEW miles left!