Can a disconnected coolant temperature sensor induce severe misfiring?

bingothegreatdog

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Sep 5, 2024
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My mother's 1992 Camry, equipped with a 5S-FE engine, has developed a little oil leak in the vicinity of the distributor. I removed it and saw that the o-ring had hardened, with some oil present on the distributor side; thus, I shall replace it.

While awaiting the arrival of the part, I reinserted it and rejoined all other components; however, I inadvertently severed one of the coolant temperature sensor connecting wires in the process. I determined that it was not essential for the automobile to operate for a few seconds, so I activated the engine, which ran very roughly, barely beginning as if the timing were significantly misaligned, before ultimately stalling. To avoid any engine damage, I turned it off and concluded the day as it was becoming late.

The next day, I detached the distributor to see if I had installed it 180 degrees incorrectly, which might result in misfiring. Despite my efforts, even with the valve cover off, it would not fit as intended, so I reinstalled it as it was the prior day. I repaired the damaged connection wire and reconnected it; upon starting the engine, it operated well.

Could a detached coolant temperature sensor be the culprit, or may it be an alternative issue, such as a loose wire or connection that I neglected to reconnect, or perhaps I inadvertently dislodged something inside the distributor during its removal and reinstallation, therefore inadvertently rectifying the problem? Appears really arbitrary. It is possible that the distributor was initially misaligned when placed into the engine, but was correctly positioned upon the second attempt. I neglected to indicate that at its first removal.

Are there any oil lines next to the distributor, or only coolant lines, in the event that another source is responsible for the leak? I am replacing the valve cover gasket and half-moons, and have just changed the PCV, grommet, and breather line; I hope this will resolve the leak.
 
If the coolant temperature sensor used for EFI is faulty, it will undoubtedly result in engine performance issues. In the absence of a signal from this sensor, the ECU enters limp mode due to its inability to determine the appropriate richness or leanness of the fuel mixture. Restore the damaged wire and reinstate the coolant temperature sensor to operational status.
 
As previously said, I repaired the connection, and it thereafter functioned properly. However, I also made some modifications to the engine, so I was curious if this was only coincidental or maybe a result of those changes.
 
The coolant temperature sensor, supposing it is the component relaying the engine's temperature to the ECU, would undoubtedly influence its operation accordingly.
You are essentially indicating to the computer that the temperature is -100 degrees, resulting in an excessively rich fuel mixture and stalling with little warming.
 
It did not operate for a sufficient duration to reach optimal temperature. It misfired immediately and operated unevenly, as if the timing was significantly off or the firing sequence was erroneous. It is difficult to comprehend that this sensor may be responsible for it, while I lack expertise.
 
Additionally, prolonged operation will result in excessive fuel richness, leading to gasoline contamination of the oil and potential engine damage.
We used to verify that by extracting the dipstick and assessing its odor. In extreme instances, one might ignite the dipstick using a butane lighter. An immediate oil change was necessary.
 
I am ready to change my oil; if I have adequately resolved the misfiring problem, I should be OK. Diagnosing a problem is challenging when many modifications are made to the vehicle simultaneously, as I have done.