ECT Sensor

tommylg · Post by **tommylg** » 10 Jan 2022, 16:45

My S70 GLT starts and runs smoothly, idles steadily at 900 for 10-15 minutes, motor temp gauge goes to "normal" and then the motor develops a miss, rpm's are erratic and it acts like it wants to die.
I have fresh NGK plugs, Bougicord wires, Volvo dizzy cap installed. All five injectors are pulsing.
My read is that something is reaching x temp and creates this motor stumble.
Reasearch says that the ECT can send a false signal on fuel and timing thus creating the misfire.
So, the questions are:
can the ECT overheat?
if not the ECT, what other sensor could be the culprit?
I have a new Valeo Sensor and Wahler Thermostat. Additionally, I have soaked the thermo housing bolts for removal.
Please respond and thank you,
Tommy

tommylg · Post by **tommylg** » 10 Jan 2022, 16:58

Additionally, the MAF displays 12kg/h and load via MAF is 0.7 volts when disconnecting it there is no difference.
The ECT displays 2.498v and 2.334v on a revisit.
Throttle Position Sensor displays 0.5 v.

Post by **Sveedy** » 11 Jan 2022, 07:45

I would say - yes. Your ect is the culprit based on the symptoms. Clean the connector when you replace it.
Can be a PITA to remove, so I notched a cheap socket for the job.

tommylg · Post by **tommylg** » 11 Jan 2022, 16:38

A Robert DIY video say to just cut the sensor wire and then you get a wrench on the sensor.
I have done a serious 5 time soak w/PB Blaster to hopefully help things along.
Thank you,
Tommy

Post by **Sveedy** » 11 Jan 2022, 16:58

Never cut wires if you don't need to.

JMHO.

Post by **Chuck W** » 11 Jan 2022, 20:49

Accessing the sensor is the issue. Not much room to turn an open-ended wrench in there. Even if you cut the wires off of the old sensor, you're still going to have to figure out how to tighten the new one with the wires attached.

Sveedy's modified socket is a good idea. Kind of like the split O2 sensor wrenches.

On my car, the old harness had disintegrated, so I'd already replaced the connection with another weather-tight connector. I just removed the pins from the connector pigtail so I could get a closed-end wrench down around the sensor to remove it. Opening up a stock connector usually invites things falling apart. If I needed to leave the connector intact, I'd go for the slotted socket.

Post by **abscate** » 12 Jan 2022, 01:02

I’m going to say no to the ECT sensor causing your misfire. It sounds like you misfire when the car is going closed loop

Did you include a new rotor in thst list?

I would search for our good friend Mr Vacuum Leak

tommylg · Post by **tommylg** » 12 Jan 2022, 15:25

Anyone have thoughts that the rotor button could be the culprit?
Anyone have thoughts onthe voltage #'s in post one amendment?
Thanks,
Tommy

Post by **Chuck W** » 12 Jan 2022, 18:11

Replace the ECT and report back.

tommylg · Post by **tommylg** » 19 Jan 2022, 16:41

I replaced the ECT sensor, thermostat, the distributor cap, and hit the rotor w/aScotchbrite pad.
The car fired right up and warmed up as the rpm's setteled in at 900.
I let it idle w/an occasional opening of the throttle and it setteled back to 900 nicely.
I drove around the neughborhood several times and took a trip to the grocery w/some trepidation, but all went well.
Let's see what happens "After the night when I wake up and see what the world will bring" - The Vikings by Flava Fav.
Once again, thanks to cn90 for the "replace the ect sensor" post.
Good day,
Tommy