gatzdon
Well-Known Member
- Joined
- July 17, 2007
- Messages
- 347
- Reaction score
- 15
- City, State
- IL
- Year, Model & Trim Level
- 2000 Exp XLS 4WD V6 OHV
I saw quite a few threads lately describing a similar problem.
If your engine is starting just fine when it has been sitting overnight, but you have difficulty restarting it when the engine is still warm; you should be checking your engine coolant temperature sensor.
If you have a '96 or later, you are in luck. With an OBDII reader and cheap/free software, you can access the PID values including, engine coolant temperature. Personally, I use Forscan Lite on my Android phone because it can pull ALL of the extended fault codes and access all of the Ford PID values.
If you are lucky, when you pull your codes, you will see the pending P0125 code and only codes related to the ECT sensor (P0115, P0116, P0117, P0118, P0128). This code indicates that the PCM thinks the engine is not warming up to temp within an acceptable time. Since you know your engine is warmed up, the problem lies with the ECT Sensor circuit with the most likely culprit a corroded ECT sensor.
If you see other codes (very likely given the age of our explorers), then you will need to make a judgement call to prioritize which codes to chase down first. Since some conditions will have a cascading effect causing multiple codes, you need to research all the codes to figure out which ones are phantom codes. Rarely will something unrelated to the ECT sensor and it's wiring cause a P0125 code, but it’s possible (for example: winter time with thermostat not restricting flow allowing the radiator to over cool the engine).
If you have a '96 or later, you can access the engine coolant temp PID values that the PCM is using. If your engine is warmed up and the temp is less than 180F, your PCM is most likely trying to compensate for a 'cold' engine. If the temp is low enough, the PCM will also try to increase the RPM’s and limit the engine power, amongst other things. Applying the cold mode strategy to a hot engine can cause all kinds of starting and running issues that look seriously bad.
If you have a '95 or older, you can easily check ECT sensor and wiring with a multimeter. (or you want to check before you buy a new sensor which is ~$20 at Autozone with lifetime warranty)
First, don't get confused, our explorers have two temp sensors. The one wire sensor is for the console gauge and has no impact on your engine's performance. The two wire sensor is to tell the PCM what the engine coolant temperature is and is the one you want to check.
Lucky me, on my V6 OHV, the ECT sensor is right out in front of the engine (at least as far out in front as you can get
).
The two things to check are the 2 wire connector and the sensor itself.
For the 2 wire connector, check for voltage with your multimeter. With the key on, engine off, and the connector disconnected, touch one multi-meter wire to the engine and the other to one of the two wires. One of the two wires should give close to 0 volts and the other close to 5 volts. If you get close to 0 and 5, then your PCM, wires, and connector should be fine. You may not get exactly 0 and 5 since the PCM supplies its own reference for the ECT sensor and you are comparing against the vehicles ground, but it should be close (mine reads ~4.8V).
Next, if you can get at your ECT sensor without pulling it, you are lucky. If not, you need to pull it to check it. Measuring resistance on your multi-meter, check the resistant across the two pins in the sensor. With our ECT sensors, the higher the resistance, the colder the temp reading. For an ECT sensor at room temp, the resistance should be about 3,000 ohms. For an ECT sensor at 190F (about normal engine temp), the resistance should be about 250 Ohms. If you see a resistance above 10,000 ohms, it means that the PCM thinks your engine is a block of ice. If you really want to be particular about checking the accuracy, you can put the probe end of the sensor in CLEAN boiling water and check how close the resistance is to 177 Ohms.
Keep in mind that the resistance to temp scale is not linear. Even a resistance reading as high as 100,000 Ohms is only -40F.
Checking your ECT sensor shouldn’t take too long with the hardest part being that ability to get at the pins on your ECT Sensor. Good luck and hopefully this helps someone chasing down starting problems when the engine is warm to hot. When this happened to me, with 260,000 miles on my original engine, the engine ran so bad, I thought I should just drop it off at the junk yard. It would take 30 seconds plus to start with the gas pedal to the floor. Even then, I would have to flutter the gas pedal to keep it running. Only got like 5 miles per gallon. Engine RPM’s would race up and down while I was at a red light. But in the end, all it took was some time researching the pending PCM fault codes (my MIL never came on) and a $20 sensor from autozone. Now she starts and runs like champ again.
If your engine is starting just fine when it has been sitting overnight, but you have difficulty restarting it when the engine is still warm; you should be checking your engine coolant temperature sensor.
If you have a '96 or later, you are in luck. With an OBDII reader and cheap/free software, you can access the PID values including, engine coolant temperature. Personally, I use Forscan Lite on my Android phone because it can pull ALL of the extended fault codes and access all of the Ford PID values.
If you are lucky, when you pull your codes, you will see the pending P0125 code and only codes related to the ECT sensor (P0115, P0116, P0117, P0118, P0128). This code indicates that the PCM thinks the engine is not warming up to temp within an acceptable time. Since you know your engine is warmed up, the problem lies with the ECT Sensor circuit with the most likely culprit a corroded ECT sensor.
If you see other codes (very likely given the age of our explorers), then you will need to make a judgement call to prioritize which codes to chase down first. Since some conditions will have a cascading effect causing multiple codes, you need to research all the codes to figure out which ones are phantom codes. Rarely will something unrelated to the ECT sensor and it's wiring cause a P0125 code, but it’s possible (for example: winter time with thermostat not restricting flow allowing the radiator to over cool the engine).
If you have a '96 or later, you can access the engine coolant temp PID values that the PCM is using. If your engine is warmed up and the temp is less than 180F, your PCM is most likely trying to compensate for a 'cold' engine. If the temp is low enough, the PCM will also try to increase the RPM’s and limit the engine power, amongst other things. Applying the cold mode strategy to a hot engine can cause all kinds of starting and running issues that look seriously bad.
If you have a '95 or older, you can easily check ECT sensor and wiring with a multimeter. (or you want to check before you buy a new sensor which is ~$20 at Autozone with lifetime warranty)
First, don't get confused, our explorers have two temp sensors. The one wire sensor is for the console gauge and has no impact on your engine's performance. The two wire sensor is to tell the PCM what the engine coolant temperature is and is the one you want to check.
Lucky me, on my V6 OHV, the ECT sensor is right out in front of the engine (at least as far out in front as you can get
). The two things to check are the 2 wire connector and the sensor itself.
For the 2 wire connector, check for voltage with your multimeter. With the key on, engine off, and the connector disconnected, touch one multi-meter wire to the engine and the other to one of the two wires. One of the two wires should give close to 0 volts and the other close to 5 volts. If you get close to 0 and 5, then your PCM, wires, and connector should be fine. You may not get exactly 0 and 5 since the PCM supplies its own reference for the ECT sensor and you are comparing against the vehicles ground, but it should be close (mine reads ~4.8V).
Next, if you can get at your ECT sensor without pulling it, you are lucky. If not, you need to pull it to check it. Measuring resistance on your multi-meter, check the resistant across the two pins in the sensor. With our ECT sensors, the higher the resistance, the colder the temp reading. For an ECT sensor at room temp, the resistance should be about 3,000 ohms. For an ECT sensor at 190F (about normal engine temp), the resistance should be about 250 Ohms. If you see a resistance above 10,000 ohms, it means that the PCM thinks your engine is a block of ice. If you really want to be particular about checking the accuracy, you can put the probe end of the sensor in CLEAN boiling water and check how close the resistance is to 177 Ohms.
Keep in mind that the resistance to temp scale is not linear. Even a resistance reading as high as 100,000 Ohms is only -40F.
Checking your ECT sensor shouldn’t take too long with the hardest part being that ability to get at the pins on your ECT Sensor. Good luck and hopefully this helps someone chasing down starting problems when the engine is warm to hot. When this happened to me, with 260,000 miles on my original engine, the engine ran so bad, I thought I should just drop it off at the junk yard. It would take 30 seconds plus to start with the gas pedal to the floor. Even then, I would have to flutter the gas pedal to keep it running. Only got like 5 miles per gallon. Engine RPM’s would race up and down while I was at a red light. But in the end, all it took was some time researching the pending PCM fault codes (my MIL never came on) and a $20 sensor from autozone. Now she starts and runs like champ again.
