Irregular EOT and ECT readings
Thread Starter
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Tuned
Joined: May 2012
Posts: 332
Likes: 42
Irregular EOT and ECT readings
I have a 04 CC F250 6.0. Lately my EOT and ECT have been all over the place the ECT has been fluctuating more than the EOT. For the past 100K miles my deltas have been within the 15 degree range. The ECT will vary up to 25 degrees from the EOT; EOT may be 180 and ECT 155. I purchased a new water temp sensor thinking that was the culprit, but haven't replaced it yet. I am using a scanguageII to monitor engine parameters. I have noticed when starting the truck in the morning the temps seem to be stored from the previous night, ex. ambient temp is 75 and SGII shows 90 then comes down to match the ambient temps. For the past few days I have been noticing the truck runs and starts smoothly until I get up to 50 mph, when cold, then starts to develop a miss until it reaches operating temps. Once reaching operating temp the truck runs smooth.
Could the ECT sensor cause this or is there something else going on, missing at hwy speeds until warmed up?
Any advice would be greatly appreciated.
Could the ECT sensor cause this or is there something else going on, missing at hwy speeds until warmed up?
Any advice would be greatly appreciated.
Fleet Mechanic
Joined: Jan 2012
Posts: 1,841
Likes: 6
If your only getting 155° ect you need a new thermostat. Ect should be 188-192. You need to see what your your temps are after the truck sits all night turn the key on and turn on the scangauge manually and wait for it to update. No need to replace a sensor till you figure out if one is bad or not. Ect and eot should be within a few degrees of each other after a cold soak.
Lead Driver
Joined: Dec 2006
Posts: 6,496
Likes: 94
From: So. Jersey
The 2 sensors are the same so you could swap them around and see if the low reading follows and reads low on oil temp after the swap.
Also when it is reading low, try wiggling the harness and connector and see if it fluctuates.
Also when it is reading low, try wiggling the harness and connector and see if it fluctuates.
Thread Starter
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Tuned
Joined: May 2012
Posts: 332
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I did the key on engine off test the ambient temp was 58 deg. My sgII displayed Fwt 71 deg and Eot was 71.3 deg. I recall the sgII use to be about 1 to 2 degrees from ambient temp. This has been after the truck has sat overnight. It seems like the Eot is close to what I am normally seeing about 185 to 190 range, the Fwt is the one that fluctuates. Would it be possible that both sensors went out? Could this cause the misfire at speed until the truck reaches operating temp?
Fleet Mechanic
Joined: Oct 2012
Posts: 1,558
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From: Bay Area
where are the sensors located?
Lead Driver
Joined: May 2014
Posts: 6,545
Likes: 13
From: Virginia Beach VA
a difference 71-71.3 is good after sitting overnight.... that proves they are both working. Nether of those sensors are out.... your thermostat is hosed! It should be ECT of 188-192 and oil above that and not more than 15* above ECT.
Could be you FICM is not at 45v or above or stiction, run synthetic oil 5w-40.
Could be you FICM is not at 45v or above or stiction, run synthetic oil 5w-40.
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Thread Starter
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Tuned
Joined: May 2012
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a difference 71-71.3 is good after sitting overnight.... that proves they are both working. Nether of those sensors are out.... your thermostat is hosed! It should be ECT of 188-192 and oil above that and not more than 15* above ECT.
Could be you FICM is not at 45v or above or stiction, run synthetic oil 5w-40.
Could be you FICM is not at 45v or above or stiction, run synthetic oil 5w-40.
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Thread Starter
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Tuned
Joined: May 2012
Posts: 332
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I recorded these on my 1.5 hour trip to work this morning.
FMP: 47 to 49
VLT: 13.5 to 13.8
BAT: 13 to 14
FLP: 13 to 13.5
FVP: 13
The reading seem pretty consistent to what I have seen for the last 100K.
FMP: 47 to 49
VLT: 13.5 to 13.8
BAT: 13 to 14
FLP: 13 to 13.5
FVP: 13
The reading seem pretty consistent to what I have seen for the last 100K.
Thread Starter
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Tuned
Joined: May 2012
Posts: 332
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I will have to check that, I am pretty sure the lowest I have seen it was 47.
Thread Starter
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Tuned
Joined: May 2012
Posts: 332
Likes: 42
I changed the Engine coolant sensor and it seemed to correct the temperature difference problem. On my 1.5 hour drive to work the deltas never exceeded 8 degrees.
I am still getting the misfire though. I did monitor the voltage when cranking and it never dropped below 47 volts.
I am still getting the misfire though. I did monitor the voltage when cranking and it never dropped below 47 volts.
Lead Driver
Joined: May 2014
Posts: 6,545
Likes: 13
From: Virginia Beach VA
Your initial post was ECT at 155°... that says the thermostat is bad and the sensors were reading correctly based on the cold soak of 71-73° by both sensors.
I'd watch it for anything less than 185° ECT. Then replace the t-stat.
I'd watch it for anything less than 185° ECT. Then replace the t-stat.
Hotshot
Joined: Jul 2005
Posts: 13,834
Likes: 25
From: Middle Tn.
Personally anything under 190 should get a new t-stat. The warmer a diesel runs, too a point, the more efficient it is since it relies on heat and compression for combustion.
