2003 4.0L loss of power, no CEL - Ford Explorer Forum - Forums for Ford Explorer Enthusiasts
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Old 04-30-2018, 02:00 PM   #1
JSargeSter
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2003 4.0L loss of power, no CEL

Hey all! Im new here- only because this is my first time around having an issue with my explorer!

I have an '03, 4.0L, XLT, 2WD, 192k miles.

I've been wrenching for years, so im here to get some explorer-specific junkies opinions before is start tearing into things.
I have no active codes.
I replaced the plugs with Autolite Platinum's about 2k miles ago. The plugs that i removed were so terrible, i have absolutely no clue how the engine even ran (i purchased the car 3 months prior)

Surprisingly, it seemed to run on all six. One day it was rough starting and had a slight miss so automatically, i figured what the hell- ill start at the plugs. I know motorcraft and autolite plugs are the go to for these engines, the autolites were on the shelf so thats the route i took.

Anyhow.. i could go drive it right now, and it will have enough power to lay down rubber. But on an occasional basis, mostly when at idle in gear or during acceleration, it almost feels as if it is running out of fuel. It hesitates, and misses. It will eventually pick up and go away in the higher RPM range. No loss of power uptop (WOT @ 3k+RPM)

Shortly after replacing the plugs, the MAF went out. I replaced it. Figured the sensor i purchased was the cause, i returned it and swapped it for a motorcraft unit. It did not change the problem.

Things ive thought about:
Upstream O2's on their way out
Fuel filter
Injectors
Debated a vacuum leak, but it does not idle high

Anyhow .. if you need more information ask away. I need this thing to be reliable, i have a baby on the way!

Thanks!

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Old 05-01-2018, 11:52 AM   #2
J_C
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Some of the following you probably already know or have checked...

At that mileage I would have changed the plug wires too, and made sure they are kept away from the exhaust manifold.

I would hook up a scan tool capable of showing live data, have it ready so you can use it when the condition pops up. It might show occasional misfires or fuel trims that aren't near 0 (might be a bit above 0 on an old engine but much above +10% tends to indicate a vac leak), might show out of range O2 sensor readings.

Running out of fuel? Sure you could have a fuel pressure problem, check it with a gauge on the fuel rail. Autozone and others provide a loaner tool free with a deposit. Unfortunately you can't climb out into the engine bay while driving to measure this but possibly you can reproduce it parked or at least it's off enough to notice parked.

At this age I would think about replacing the fuel filter but doubt that's it because if clogged, it should manifest the problem more constantly. I'd sooner thing the fuel pump or fuel pressure regulator on the in-tank sender unit "IF" there is a fuel pressure issue. Your '03 has a returnless fuel system and should be around 60-70 5PSI, if I recall correctly, and should hold pressure for a few minutes at least, from just turning the ignition key the first notch to the run position (not start yet) with engine off.

Injectors, sure it's possible but I would expect specific cylinders to start misfiring first, not all of them starting to do it at the same time, and yet they are the same injectors using the same fuel so if one were failing due to a clog or mechanical issue either way, might be time to replace all of them. If nothing above pans out then I'd put Techron fuel system cleaner in your next half tank of gas.

Cheapest way I know to get the live data is get one of those bluetooth OBDII dongles, something like the BAFX on Amazon which goes for around $22, links up to an android phone/tablet/etc with bluetooth or some other similar product that uses wifi instead of bluetooth for Apple devices, then use Forscan app for the most functionality or in this case Torque app might be enough.

Considering the mileage and age you could just replace the O2 sensors. I hate to throw money at things unnecessarily but eventually they are going to fail and there's no getting around them building up soot over the years and providing a little less accurate reading - often replacing them will raise fuel economy slightly... which isn't enough to me to justify getting new ones if there's no problem, but with a problem it might sway me to replace them with the consolation that it wasn't a waste of money long-term if that didn't fix the problem.

Other issues, say you find a specific cylinder is misfiring and test the compression and it's good, check the spark plug and wire and they're good, if you suspect the injector you could get new injector o-rings, swap the injector to a different cylinder and see if the problem follows the injector to the other cylinder, but I'd have put fuel system cleaner in and ran through that tank of gas and most other things mentioned above, long before I'd start taking the fuel rail off to do that.
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Old 05-07-2018, 06:31 AM   #3
tru-blue
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Welcome. Good advice from JC. Good luck with it.
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Old 05-07-2018, 04:46 PM   #4
sport40
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hey sounds like either your injectors are breaking down or your cats are plugged up, i had similar prob and hollowed mine out and it cured the problem.if you can use newer model injectors they are better, i used 2006 mustang.
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Old 05-07-2018, 05:41 PM   #5
J_C
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^ If the original injectors lasted 15 years and 192K mi, wouldn't another 15 yrs and 192K mi with stock injectors be long enough?

It reminds me of a different forum where there are people with 20 year old vehicles and their dash light bulbs are going out and people are suggesting that they'll get longer life if they switch to more expensive LED bulbs... as if another 20 years wouldn't be enough.
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Old 05-07-2018, 07:23 PM   #6
sport40
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LOL...i suggested 2006 mustang injectors because they are better, i didnt say used ones, i bought new ones(rebuilt) mine had 160,000 when i replaced them they where way out of resistance range...
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Old 05-07-2018, 11:16 PM   #7
J_C
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You totally missed the point. There is no reason for "better" if the originals lasted 15 years and it's not going to be an early failure point 15 years from now.

It won't run better with mustang injectors. It won't achieve more power or fuel economy (if higher flow injectors then they could be needed if there were other more extensive engine mods to get there).

2006 Mustang 4.0L injectors don't even have the same electrical connector so you'll be lopping off all the original wiring harness connectors and buying 6 new ones to solder or crimp on, or pulling them off a junkyard vehicle. More time and expense for negligible benefit.

There isn't any reason to substitute them now. Makes no sense, unless you have those lying around, then it makes perfect sense, to just save money by not buying more parts for a low value vehicle, except it'll still be a PITA to rewire the injector harness for them.
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Old 05-08-2018, 04:58 PM   #8
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My point was. it will clear his rough idle. and miss problem and will also give him better fuel economy.
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Old 05-08-2018, 05:41 PM   #9
J_C
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^ Except that we don't know for sure that it is the fuel injectors, and it would be a shame to hack up a wiring harness just for injectors that may not be needed, then have to use them anyway or un-hack the fuel harness back to factory state.

There are several things that can lead to the symptoms and we don't have any follow up info yet. He can check a lot of that without spending any money or doing any major surgery to the vehicle yet.
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