Cross country road trip was a success, but I may have some problems?

[Harley McIntyre]

Roughly 20mpg the whole way which was nice, however when monitoring my coolant temperature with my scan tool, I noticed it would have random drops to -40 and sometimes jumps to 234 and 304, even once with the engine off it jumped to 304, every time was only for a split second, is this a bad cylinder head temp sensor?, Also I noticed when idling my fuel pressure would jump to between 50-65 psi, usually 65 and it would stay there until I started moving again then would go back to 40 psi, vacuum leak? Bad regulator?, Last thing, while engine braking down the steep grades, my rpm would start rapidly fluctuating (see attached picture) and it would almost feel like the vehicle would stop engine braking for a split second then start again and go back and forth doing that, but it only started doing this after I was going down the grade for a bit. Any suggestions?
My coolant temperature on average though would stay at 205ish, but 207 if the AC was on full blast, I always turned it down when going up grades, I really think the cooling system for the v8 explorer's is extremely under engineered, my moms (now gone) expedition would stay at 189 the whole time in 90+ degrees with the AC running and the 5.4l although she had electric fans so maybe that's why. Pretty stupid of ford to use the same radiator for the v6 and the v8 imo but maybe mine is just meh, I'm planning on replacing my radiator with an all aluminum one that's basically the exact same design but just all aluminum which should definitely help with cooling.

 

[94Eddie]

It could be problems with deterioration of wire insulation. Early 4th gen models are know to have these problems in their wiring harnesses. Was there any physical symtoms of the issues indicted by the readings? For instance was there a coolant loss from actual overheating etc.?

 

[Harley McIntyre]

It could be problems with deterioration of wire insulation. Early 4th gen models are know to have these problems in their wiring harnesses. Was there any physical symtoms of the issues indicted by the readings? For instance was there a coolant loss from actual overheating etc.?

Nope, it never actually overheated, but would get somewhat hot going up grades, I've thought it could be the wiring harness too but I honestly have no idea where to start looking, other than just replacing the whole harness which is a nightmare

 

[Bill MacLeod]

Have you checked for any stored codes? Has the ecu gone into fail safe mode when you monitored any extreme engine temperatures?

What cooling system components have been replaced or are they all still original?

 

[Harley McIntyre]

Have you checked for any stored codes? Has the ecu gone into fail safe mode when you monitored any extreme engine temperatures?

What cooling system components have been replaced or are they all still original?

Yes, I haven't had any new codes for at least 8 months and the most recent was for the fan clutch, roughly 3 weeks ago I replaced my fan clutch, water pump, and I'd say 95% of the coolant, and actually when it had those random split second spikes, nothing happened, that's why Im thinking it must be a bad sensor, unless I still somehow have air in the system, but at this point with how far I drove, it should have bled the system the rest of the way

 

[94Eddie]

Nope, it never actually overheated, but would get somewhat hot going up grades, I've thought it could be the wiring harness too but I honestly have no idea where to start looking, other than just replacing the whole harness which is a nightmare

I don't think replacing the entire harness is justified at this point. I would start by looking at the wiring from the sensors to where it goes into the harness for any deterioration. Then start checking output voltages etc. Dealing with wiring problems is not one of my stronger areas of trouble shooting. There are a lot of YouTube videos on repairing these type of problems. Also, someone with a very good scan tool and knowledge of how to use it well can probably track down where the problem is located by reading real time data outputs.

 

[Harley McIntyre]

I don't think replacing the entire harness is justified at this point. I would start by looking at the wiring from the sensors to where it goes into the harness for any deterioration. Then start checking output voltages etc. Dealing with wiring problems is not one of my stronger areas of trouble shooting. There are a lot of YouTube videos on repairing these type of problems. Also, someone with a very good scan tool and knowledge of how to use it well can probably track down where the problem is located by reading real time data outputs.

My scan tool can read mode 6 data, so that might work but I'm not sure, I'll have to look into what it can show me. Hopefully I just have a vacuum leak somewhere, considering my high idle I must have one at least, I'll just have to check for any leaks with some smoke

 

[MNgopher]

Well, if you believe the cooling system is undersized due to the radiator, you may be surprised to learn the radiator in the Explorer, including the V6's, is actually larger than the radiator in the F150's and Expeditions of the same generation using the same size or larger V8's by roughly 5%. Different shape and configuration, but hardly"undersized".

The wide fluctuations in temps (particularly the -40 reading, which is often the bottom of the temp many temp sensors have in their range) point to a sensor or electrical fault. Not a physical one.

That being said, what kind of fan clutch did you install? Aftermarket or Motorcraft/Ford? My experience with aftermarket fan clutches has told me these are virtually always an OEM only replacement as the aftermarket ones are so inconsistent...

 

[Harley McIntyre]

Well, if you believe the cooling system is undersized due to the radiator, you may be surprised to learn the radiator in the Explorer, including the V6's, is actually larger than the radiator in the F150's and Expeditions of the same generation using the same size or larger V8's by roughly 5%. Different shape and configuration, but hardly"undersized".

The wide fluctuations in temps (particularly the -40 reading, which is often the bottom of the temp many temp sensors have in their range) point to a sensor or electrical fault. Not a physical one.

That being said, what kind of fan clutch did you install? Aftermarket or Motorcraft/Ford? My experience with aftermarket fan clutches has told me these are virtually always an OEM only replacement as the aftermarket ones are so inconsistent...

Wow that's surprising to be honest, I guess these engines really just put out that much heat then, or it's the inefficiency of the fan clutch design, and I used motorcraft everything except for the thermostat cause it was like $20-30 which is insane for a thermostat. I guess I get to do a full inspection of my engine wiring harness then and check for shorts. Does the insulation just strip off the wires? Or does it melt away or what? Just wondering if it's something I can patch up

 

[Bill MacLeod]

I would suspect a malfunction with your scan tool. The fluctuations in temperature readings are just too extreme.

 

[Beachcomber86]

Everyone that has a 2006 or 2007 Explorer should look at this thread BEFORE spending a lot of money. Checking for and fixing these issues will prevent a lot of tail chasing!

Found my ghosts in the machine

Hey guys, If you've got unexplained, and intermittent, problems, here's a possible cause. My Ex has developed what is best described as the "hiccups" at idle. It doesn't happen all the time, and feels like a misfire. No codes, though. So I thought I'd just inspect the engine for (esp the...

www.explorerforum.com

 

[zerodevil]

If you have a 4.6L, check for cheap/failing ignition coils. Ford ran pretty much the entire wire harness for the vehicle directly over the top of 3 or 4 of them. Cheap coils, and coils that are failing start throwing off EMI, and it doesn't take a whole lot of induction from a 25,000 volt coil to mess with sensors reading 1-12 volts. Can cause all kinds of funky behaviors, including loss of communication with the transmission.