2002 Explorer 4.6L dies when warm

[ab_slack]

Seems to start fine and run fine till it gets warmed up then suddenly runs rough and stalls. My guess the issue is when tries to get into closed loop operation.

Prior to this, about 4 days ago I got a CEL and P0174 code, later P0171 as well but it was continuing to run well. I was getting ready to do some diagnosis when new behavior started. Reading I did suggested most likely it was vacuum leak or O2 sensor. I have had the occasional intermittent codes about O2 heater for a few years under harsh conditions that always cleared so was suspicious of O2 sensor.

Just after it started shutting down I was taking a look at how accessable the O2 sensor are and saw the passenger side downstream connector had melted against exhaust. Melted pretty badly. The connections didn't appear as if they open but signals could have shorted against exhaust.

Does it make sense that bad connection to the O2 sensor could cause the symptoms I see when warmed up? if one of the connections shorted (4 wires) to the exhaust, is there a fuse I should check?

Thanks,

Andrea

 

[Josh B]

Do you drive it at night? After some miles at highway speeds if you stop in the dark somewhere(maybe in your case at home) somewhere there's no lights look underneath at the catalytic converter(just to rule that one out) If it's glowing red you'll know

 

[ab_slack]

Do you drive it at night? After some miles at highway speeds if you stop in the dark somewhere(maybe in your case at home) somewhere there's no lights look underneath at the catalytic converter(just to rule that one out) If it's glowing red you'll know

What would I be looking for? I can't really drive it any distance right now since it dies as soon as it warms up

 

[ab_slack]

Just a follow up. Replacing the connector and O2 sensor seems to stop it from stalling. I had a couple hiccups after but that may have been from a hill climb and low fuel.

 

[alwaysFlOoReD]

Hopefully that cured it. Let us know how it goes...

 

[ab_slack]

Hopefully that cured it. Let us know how it goes...

It worked for a couple hundred miles fine and then I started getting some hiccups. Now it starts and runs, but not quite right, after a minute it gets very rough and stalls. After a few instances it spit out a P0351 code. Ignition coil A primary secondary circuit. Is coil A cylinder 1? I've never had this kind of symptom with a bad coil. Since it is an 8 cylinder, it loses power but the other 7 keep it going.

 

[alwaysFlOoReD]

I don't know. Hopefully someone else sees the question.

 

[acsnowrider]

Seems to start fine and run fine till it gets warmed up then suddenly runs rough and stalls. My guess the issue is when tries to get into closed loop operation.

Prior to this, about 4 days ago I got a CEL and P0174 code, later P0171 as well but it was continuing to run well.

Just after it started shutting down I was taking a look at how accessable the O2 sensor are and saw the passenger side downstream connector had melted against exhaust. Melted pretty badly. The connections didn't appear as if they open but signals could have shorted against exhaust.

Does it make sense that bad connection to the O2 sensor could cause the symptoms I see when warmed up? if one of the connections shorted (4 wires) to the exhaust, is there a fuse I should check?

Thanks,

Andrea

YES--The melted/shorted O2 can, when the system goes "closed loop", trash fuel control--Repair what is "known" first, then go from there--You may still need to address the P0171/174 codes, but I had several over the years, with shorted O2 sensor, and upon going "closed loop" wouldn't run properly. Cold start (open loop) , engine ran/with "high idle".

 

[ab_slack]

YES--The melted/shorted O2 can, when the system goes "closed loop", trash fuel control--Repair what is "known" first, then go from there--You may still need to address the P0171/174 codes, but I had several over the years, with shorted O2 sensor, and upon going "closed loop" wouldn't run properly. Cold start (open loop) , engine ran/with "high idle".

The codes went away. But if you see my other follow-up post, after most of a week of a bunch of small trips and four 50 mile trips...a new problem with stalling that threw a P0351code. When cold it ran fine and at least one warm up didn't re-occur. Not the most reassuring when I have a thousand mile trip coming up Tuesday night and then another 1500 miles next week

 

[acsnowrider]

The codes went away. But if you see my other follow-up post, after most of a week of a bunch of small trips and four 50 mile trips...a new problem with stalling that threw a P0351code. When cold it ran fine and at least one warm up didn't re-occur. Not the most reassuring when I have a thousand mile trip coming up Tuesday night and then another 1500 miles next week

I don't have any manual access anymore, but if memory serves me, P0351 is primary side of coil, cyl # 1--Generally, caused by one of three things-Bad coil, problem with wire from coil to PCM/computer, and the Computer itself/internal issue. Over the years, I've had to replace/repair all three, but not a code you routinely see! Driving a extended amount of mileage, with a misfire can trash the catalytic converter, due to excessive raw fuel entering the converter. Changing the coil is a pretty quick check, but if I was out on a long trip, and had a issue like this, HAD to keep going, I'd pull the connector at the injector, on the cyl with the issue, shutting off the fuel delivery, and get it fixed when I could.

 

[ab_slack]

I don't have any manual access anymore, but if memory serves me, P0351 is primary side of coil, cyl # 1--Generally, caused by one of three things-Bad coil, problem with wire from coil to PCM/computer, and the Computer itself/internal issue. Over the years, I've had to replace/repair all three, but not a code you routinely see! Driving a extended amount of mileage, with a misfire can trash the catalytic converter, due to excessive raw fuel entering the converter. Changing the coil is a pretty quick check, but if I was out on a long trip, and had a issue like this, HAD to keep going, I'd pull the connector at the injector, on the cyl with the issue, shutting off the fuel delivery, and get it fixed when I could.

That is what I have been reading. That it is one of those three causes. For diagnostic purposes I did exactly what you said and disconnected the fuel injector and coil pack for cylinder #1 and it wouldn't stay running. On a few past occasions, I've had to run on 7 cylinders including one where it blew a spark plug out in the middle of the night and plug and coil pack were lost on the road. I could tell power was down but in all those occasions it ran fairly smooth.

It ran so horrible I was wondering if the timing got messed up somehow, maybe even the timing chain had jumped a tooth if such is even plausible, but after cooling down it started and ran smoothly. Could still be wiring or the PCM I supposed. Yuck to both those.

 

[acsnowrider]

To clarify, unhooking the injector, was something I would do to protect the Catalytic converter!! To diagnose some of your issue, swap the coil to another hole-clear the codes, reset the KAM (keep alive memory-this resets fuel trims, ect back to default), and retest with nothing unhooked. If the coil is the cause, the code should, in theory, switch over to the new position/follow the bad coil. Blew a plug earlier?? Must have quite a few miles on her???
And I replaced ALOT of Coil on Plug coils! many more than PCM'S/circuit repairs. Hope this helps.

 

[ab_slack]

To clarify, unhooking the injector, was something I would do to protect the Catalytic converter!! To diagnose some of your issue, swap the coil to another hole-clear the codes, reset the KAM (keep alive memory-this resets fuel trims, ect back to default), and retest with nothing unhooked. If the coil is the cause, the code should, in theory, switch over to the new position/follow the bad coil. Blew a plug earlier?? Must have quite a few miles on her???
And I replaced ALOT of Coil on Plug coils! many more than PCM'S/circuit repairs. Hope this helps.

Thanks. I didn't think of resetting the KAM after I did the fix on that one melted O2 sensor connector which involved replacing the sensor as well. So that maybe that is related?

I swapped out the plug and coil on cylinder 1 for the new today to eliminate that. All the coils and plugs were replaced about 50K miles ago, Autocraft plugs and genuine ford coils. Putting in the new parts made no difference.

Last night after the issue cropped up, it started fine after 30 minutes left off. I had not replaced parts yet. This morning it ran fine. After replacing parts it ran fine, then I proceeded to get it hot to see if I could reproduce. It warmed up, no issue until I turned off the inigition and then restarted it. Then it wouldn't run right and stall. I did that again and again with same result and eventually it started and ran fine again. So puzzled by that.

Yes quite a few, 312K miles. Engine was replaed about 160 K mile ago. The plug blowing out was somewhere around 190K miles (30K miles on the remanufactured engine).

 

[acsnowrider]

Wish I had a wiring diagram for your rig--Does your 2002 have a relay, powering up the pcm/computer??--if so, replace it!! Almost sounds like your getting weird voltage, to the computer. I replaced a lot of these, and they caused really strange issues, some of which happened while the vehicle was running.--resistance in the relay,(or else where, if no relay) would trick the computer/make it think a restart had happened, when it didn't, and ect. Just a thought

 

[ab_slack]

Wish I had a wiring diagram for your rig--Does your 2002 have a relay, powering up the pcm/computer??--if so, replace it!! Almost sounds like your getting weird voltage, to the computer. I replaced a lot of these, and they caused really strange issues, some of which happened while the vehicle was running.--resistance in the relay,(or else where, if no relay) would trick the computer/make it think a restart had happened, when it didn't, and ect. Just a thought

there is a relay and I just swapped it with the blower mower. Both the same part number relay. If that was an issue it should make a difference. There are so many things interacting it is hard for me with my limited experience to find a solid footing. I have learned lots, found some vac leaks, possibly a big one, but just not sure. A new MAF sensor seems to cause more problems than the existing. Maybe the existing is not right and hiding a problem that I see with the new sensor, Just don't know