04 4.0 Hesitation

[mikeinri]

Hey guys,

I have a 2004 Explorer, 4.0 L, with 170,000 miles.

The engine starts, idles and drives fine. However, when cruising along, and lightly pressing the gas (such as to climb a slight hill), the engine seems to hesitate like it's skipping.

Replaced plugs, wires, fuel and air filter, even the harmonic balancer and belt (they were due anyway), changed oil; no improvement.

There is a ticking noise at idle, sounds like upper internal.

Mechanic pulled valve covers, says valves and springs look good.

What's left? Is this likely to be as simple as the coil pack? Any other ideas?

Mike

 

[Dave8338]

Have you checked the fuel pressure at the rail, yet ? Original fuel pump ?

 

[mikeinri]

Yes, original fuel pump. Why would that cause it to run OK except as noted?

Mike

 

[Dave8338]

If your pump is working well enough to run on level grade or at idle, it may still see a pressure drop significant enough to cause a slight starvation under heavier loads. Best way to confirm that is to connect a fuel pressure gauge to the valve, with a long enough hose to reach up to the wiper where you can see the gauge face. Then take it out for a drive and see what your pressure readings do under various loads.

Cheap / easy way to rule out a fuel pump.

 

[mikeinri]

How does one rule out the coil pack? My wife had a Pontiac which behaved in a similar way, turned out to be the coil pack.

The fuel pump would be a last resort, I hope, given that you have to remove the tank to replace it, correct?

Mike

 

[Dave8338]

Coil packs can, if shorting to open air, be seen by spraying them with some window cleaner in a dark setting (at night). If they fail internally, there is little than can be tested without swapping out another unit.

As for the fuel pump replacement, yes... you have to lower the tank to replace it.

 

[mikeinri]

Thanks Dave.

In general, I hate part-swapping, but the coil would be a very easy thing to try.

Not sure if this could be related, but the thermostat housing blew out on me a few weeks before I noticed this problem. The top of the engine (including the coil pack) was completely covered in coolant.

Any way that could contribute, and in what way (what else might have been ruined)?

Mike

 

[mikeinri]

The skipping problem is worst right around 1500 RPM, especially noticeable when cruising along in OD.

There is also a lot of mechanical rattling or tapping noise at the front of the engine at idle, sounds like top, passenger side, but tough to tell.

Mike

 

[mikeinri]

Ugh. New coil pack, same problem. Runs fine except at 1500 RPM...

Mike

 

[mikeinri]

OK it's getting rougher under 1900 RPM in general now, and now there's a CEL...

Mike

 

[Exproblems]

The fuel pump would be a last resort, I hope, given that you have to remove the tank to replace it, correct?

Mike

Yes, removing the gas tank is the "correct way" and more expensive way to take out the fuel pump, but I saw a post in here a while back, where a forum member cut a 3 sided hole (peeling back the floor plate) thru the floor board in the rear, passenger seat foot well, where he gained access to remove and repair the fuel pump. I'm sure that post can be found using the search box at the top of the forum if you are interested in that method. His post has photo's and the directions to do it this way. Just something to consider according to how much work or money you would want to put into a vehicle that is nearly 10 years old and has 170K miles on it.

BTW, I found the link to that post where the guy cut the hole in the floorboard to remove the fuel pump. It is post #1, written by "High Order 1".

http://www.explorerforum.com/forums/showthread.php?t=322730

 

[Exproblems]

There is also a lot of mechanical rattling or tapping noise at the front of the engine at idle, sounds like top, passenger side, but tough to tell.

Mike

Mike,

pray that rattling noise you hear isn't the front/left bank cylinders, "timing chain" going bad on you. The rear timing chain controls the right bank cylinders, which is my current problem. A "rattling" noise in the 4.0L engine has been known to be a broken apart, plastic "timing chain tensioner guide". Those broken pieces can cause havoc in the motor. The front timing chain can be repaired with the motor still in the vehicle.

 

[swshawaii]

OK it's getting rougher under 1900 RPM in general now, and now there's a CEL...Mike

Any trouble codes?

 

[mikeinri]

Codes as follows:

P0300

P0303

P0316

P1000

Mike

 

[swshawaii]

Logic would say remove the "not so easy" #3 plug and wire for inspection. Keep posted and GL.

 

[mikeinri]

Dumb question, but if I remove the #3 wire and try to start the engine, would that hurt anything? Just want a quick sanity-check to see if it actually gets worse when the wire is removed.

Mike

 

[Exproblems]

Dumb question, but if I remove the #3 wire and try to start the engine, would that hurt anything? Just want a quick sanity-check to see if it actually gets worse when the wire is removed.

Mike

I can't see pulling one spark plug wire off of the spark plug tip doing any damage to the engine while it is running other than possibly throwing a CEL code warning and make it run rougher on 5 out of 6 cylinders. I'm thinking it may throw a code because when I changed my spark plugs for the first time in my EX, one of the plugs rolled off of a small table in the garage and fell approx. 2 1/2 feet to the floor. I thought nothing of the short fall to the floor damaging the spark plug in any way, seemed harmless enough, but after I fired up the engine, it ran rough and threw a CEL code on the fallen plugs cylinder. Turned out the short fall to the floor bent the plug tip inward closing the plug gap I had set prior to installation, throwing the gap way off and setting off a CEL code.

 

[zpn_by]

Mike, did you by any chance double check the wire for #3? Or, is it possible your injector or wiring for #3 got contaminated by the coolant blowout? Generally two causes for a misfire - no spark or no fuel. With new plugs, wires, and coil pack, the spark should be OK. Next is the fuel system. As it's only one cylinder reporting a problem, I'd check that injector and its wiring first.

 

[mikeinri]

One of those codes was multiple misfires at startup. It seems to run fine over 2000 rpm.

The coolant leak was all over the top of the engine, sprayed out of the thermostat housing on the top front of engine. Not sure how that could get into the injectors. I was worried about the coils, but I've replaced that.

I do have another garage that I could bring it to for a fuel problem.

It's terrible that I have two dealers near me, but can't trust either of them not to screw me over.

Other than the codes, this problem existed before changing the plugs, wires or coil pack...

Mike

 

[swshawaii]

Not uncommon for #3 to be damaged installing. Since access is restricted at an awkward angle, the porcelain can easily break, or the plugs ground strap gap can close when bumped on the snout. Disconnect the wire at the coil and tie it far away as possible. Start and run the engine for a few seconds. The best method is still removing the plug for inspection.