Might have some serious issues...

[MgMatt]

So I bought a 2004 Explorer 4.0 SOHC 2WD not too long ago, it had the check engine light come on not too long after, had the codes ran a P0193. but I had ignored it a couple days. After a couple days, my battery was dead and after it not holding a charge overnight, went and bought a new battery. The truck was running smoothly again for a couple days and the check engine had even turned itself off. But now today I go to start it, its making a horrible ticking noise (which after doing some research could be timing chain/timing chain tensioner/ or lifters or maybe something else) I also seemed to have a small oil leak today that seemed like it came from the chain tensioner (I think) either that or some gasket, oil had fallen onto the manifold below so it had some white smoke. But since the check engine light was on again, I figured maybe I'd pull up a definitive code so I can figure out the ticking, But to no avail, the code was just the P0193 again, which is "Fuel Rail Pressure Sensor High Input".

Also to describe the ticking more, it doesn't seem to happen at startup, maybe 30 seconds after cranking over, and gets not increasingly loud but increasingly faster with the rpms, but if I keep them low or coast then it doesn't seem to make it at all. I'm honestly way more frightened with the noise than the code, I can deal it with running choppy or rich for now as I have little to no money to fix. If anybody could help me that'd be cool Thanks

 

[Drewmcg]

How many miles on this motor? When was the last time the fuel filter was changed? Any performance issues (e.g., does it accelerate strong and smooth, or does it bog down?)?

Assuming you're keeping oil level topped off, your oil drip is not a priority. Except that if it really is coming from were one of the (two) tensioners screw into the head(s), then it might be a clue that the prior owner had concerns re. the timing chains and maybe pulled or replaced one or both tensioners to deal with it.

I'd (i) ask the prior owner some detailed questions, starting with where he had the truck serviced, and moving onto the timing chain topic;
(ii) you might go to the seller's local Ford dealership and have them run the VIN to see what, if any service, they've done on this truck. Could be they've already diagnosed a timing chain issue.

There are three (actually, four if its a 4X4 or balance shaft engine) timing chains: a primary and two secondary timing chains. The primary and the left (drive side) chains are on the front of the engine; the right (passenger) side secondary chain is on the rear of the engine. You basically need to pull the entire engine to repair that right (rear) timing chain. Big, expensive job. So if you finally nail down a timing chain problem, try to figure out which chain it is. If its one or both of the front chains, they can be replaced without pulling the engine, saving $$$.

The timing chains don't typically break--the guides do, causing rattle and, eventually, the chain to slip. This is an "interference" motor, so when that happens pistons hit the valves, and all kinds of bad things happen. Chunks of timing guide break up and clog oil passages (even the oil sump intake, potentially) causing even bigger problems.

I don't recommend driving the motor if there's a bad timing chain problem. You might make it 20k miles or 2k miles or 200 miles--but you'll never know when or where the motor will quit. If its really a timing chain issue (it might not be), either get it fixed or sell the truck and tell the prospective buyer you think its got a timing chain problem. If the body is in good shape, someone will buy it and fix it before the motor is truly trashed. Good luck.

 

[imp]

@MgMatt @Drewmcg
OTOH, from what I recall hearing over and over, is that failed/failing chain guide(s) make most noise upon initial start-up, tend to diminish or stop when the hydraulic tensioners get oil pressure. Some suggest starting with the pedal to the floor!

Am I on base with this or no? Valve lifters can make quite a clatter; usually it's just one, so the click only occurs every 2 crankshaft revolutions, therefore giving it a fairly low repetition rate at idle speed. I'd try stethoscoping along the valve cover tops to attempt to pinpoint if noise is originating away from the chain areas.

Regarding the P0193, this is a 2-function sensor, Fuel Pressure AND Temperature Sensor, new for 2004, needed for the new returnless fuel charging system. It is vital to fuel pump speed regulation, and "put the fear" in me when I got the code. IOW, if the sensor quit providing data, would the fuel pump stop running (in B.F. Egypt, of course)? Ford Engineers thought of that possibility, so if PCM stops getting data to run the fuel pump, it shifts to "full-on" operation, dumping the excess fuel volume generated right back in the tank. This ain't good either, but better than breaking down somewhere. I replaced the bad sensor. Agree that IF the noise is thought to be chain-related, it takes precedence over the P0193. imp