Ford 4.0 SOHC Timing

[mk378]

A neighbor has a 2005 Ford Ranger 4x4 with 4.0 engine, 206k miles. He brought it to me with a "misfire" -- meaning it would barely run or move. He wanted me to change the spark plugs, as they were original. I said that was unlikely to solve the problem but since he'd already bought new plugs I did it anyway. The old plugs were completely shot, they were base metal and worn down to about 0.100 gap.

Now it does at least start up and idle, though it has some misfiring and something is clearly not right. It does not make any rattling or other noises that others say are from the timing chains. On a test drive the engine has absolutely no power, the truck can't go more than 5-10 mph on a slight uphill.

Further interrogation revealed that he went to another amateur mechanic who did something related to a water leak near the thermostat and something related to the timing chains and it hasn't run properly since. This loss of performance occurred suddenly either just before or related to that work (It's really hard to communicate with the owner). I do see there is a new tensioner piston on the side of the left head, I didn't look for the right one. I did take the cam sensor out and look in the hole to confirm the left cam is at least turning.

The only OBD code is EGR flow because the DPFE sensor has melted and fallen apart, I plugged up the silicone lines and left it unplugged. There aren't any codes related to misfiring or crank or cam sensors. Engine coolant heats up to exactly 180 degrees, suggesting a 180 degree thermostat has been installed which is a hallmark of someone who doesn't know what they're doing.

So my question is are there any simple checks to make from outside to confirm the cams are in time? I'm thinking remove the valve covers and check the slot in the end of the cam is the only way.

Also I'm kicking around the idea that the cat may be melted and clogged, since those old spark plugs would have had some severe misfiring. The secondary O2 does exactly follow the primary-- not good-- but I likely didn't run it long enough to get a P0420 code. What is the best simple test for clogged cat?

 

[K-Man]

The 4.0 V-6 of that vintage Ranger had timing chain problems, and you wouldn't necessarily have any noise. Sounds as if your neighbor neglected the truck, which helps cause those issues. The backyard mechanic might not have known what he was doing when he messed with it.

So I would still suspect timing is (at least partly) to blame, and the obvious place to start is the chains. Working on the system is a real pain—just check the Ranger and Explorer forums to confirm this. The Haynes manual for the Ranger recommends removing the engine to do the work.

 

[BigCahuna]

If it were mine, I'd check each spark plug wire to be sure they are at least making a spark to the plugs. My '02 had one of the coils go bad and that was my miss. Start with the simple stuff first.,,,

 

[Rand]

IIRC: Chains are a pain one is in back the other in front.

 

[Kira]

The replaced tensioner on the left (driver's head, yes?) makes me think they know something's wrong.
Access to unscrew the right tensioner requires some disassembly. Any deeper work on the right (passenger's side) side requires removal of the engine.
2005 and later had the revised chain tensioners so ekrampitzjr's opening statement above is off target.
Earlier version had a weak spring which allowed wear until the oil pressure increased upon startup. Even then failure wasn't assured. Neglect maybe struck again.

See if the PCV valve is intact. It sticks out of the BACK SIDE of the left (driver's) valve cover and goes right up against the firewall. A plastic pipe goes from it, makes a 90* turn to cross behind the engine then takes another 90* turn to go to the intake.
It's a 16" L. It cracks at the ends and splits on the underside. The PCV valve itself "1/4 turns" into the valve cover and the plastic lugs involved can break. No "twist-lockability" with a good PCV valve means a new VC. The PCV L is a huge potential vacuum leak.

Get the single cylinder leak down test positions and see if the pistons and valves hold air. I'm not sure how to physically check the cams for correct position aside from that or attaching a cam locking tool.

Also see if your IAC valve is functioning. It sits atop the throttle body and is the only regulatory mechanism to set idle speed. Remove it and fire the truck up. It will move ~9mm but it will move.

See if the throttle cable and positioning sensor are intact.....or that the screw holding the working end of the throttle cable is tight.

Maybe the fuel filter is solidly clogged?

 

[t1snwrbrdr12]

(I may be mixed up a little because I work on USPS Ford 4.0, so our intake and a few things differ)

The driver side head / timing chain guide has a screw that likes to back out (it’s behind the p/s pump and bracket on our vehicles). If that screw backs out and you can find it, we can tinker with the chain guide and get it all back together. This may have happened to your neighbors. I’ve re-installed quite a few and had no issues after (noise ceases, timing is on)

That said, you need the dpfe sensor. It samples baro pressure at key on to set the fuel curve / maps.

I don’t know exactly why that likes to melt down, ours do randomly (seldom, but some do). We replace them and the hoses and are fine. Without the dpfe functioning correctly you shouldn’t chase down other issues. Fix the obvious and simple first.

 

[Kira]

Remember, the 4.0l OHV was gone by 2000 when the S.O.H.C. 4.0l took fully over. Gotta know which engine.
Any 2005 Ranger 4.0l will be the SOHC (Single Overhead Cam).....no idea what a "USPS 4.0" is.
I was told by a Ford mechanic that the DPFE can rot out (highest plastic part the 2 hoses go into) but never read that they melt>>and I'm not a mechanic. Good to know.

 

[Timmastertech]

Yes, there are ways to verify valve timing without taking the engine apart. On that engine there is only one cam sensor so looking at cam/crank sync with an oscilloscope would only tell you whether that particular camshaft is out of time, but not the other cam. Using a scope and pressure transducer in cylinder would be the preferred method looking at at least one cylinder on each bank. That said, that is a technique that takes a lot of time, training, and a significant tooling investment to master. Beware as well that there are no timing marks on that engine. To check or set cam timing you would need to pull the valve covers then there is a jig that goes around the reluctor wheel on the crank pulley to set the crank and then a jig that goes in the end of each cam to lock them.

 

[Junk]

Melted plastic DPFE sensors on Fords usually mean a plugged cat, if it were me I'd start with either checking the back pressure or unbolting the y-pipe from the manifolds and seeing if it runs any better; it's a lot less invasive than timing chains on these. As previously stated if you're doing chains on both banks the engine comes out.

 

[K-Man]

Kira said, "2005 and later had the revised chain tensioners so ekrampitzjr's opening statement above is off target."

Thanks. Couldn't remember whether '04 or '05 was the last year for the problem tensioners.

 

[The_Eric]

If it's primarily just way down on power, but running most smoothly, I would investigate a plugged converter.

To me, they have their own feel and sound. Pull an upstream o2 sensor and check back pressure.