I ordered a replacement coolant temperature sensor in an attempt to fix my annoyance of the Caravan's hot-restart minor stumble. It bugged me because it has done it since new and my Father in-laws which is a 2017 that I have driven enough didn't so while it was nothing to panic about it did bug me. (OCD)
Anyway... I had gapped the plugs, scoped it, read for codes, looked at each cylinder on my dad's scope, and looked at the oxygen sensors and couldn't seem to figure it out.
Finally I decided for the whole $10 USD that a new temperature sensor was worth a shot and it looked easy to change so I thought I would take the chance and try that and if not that I would look into the Map Sensor.
Before I put it in I measured the ohms at room temperature and at 32F (0c) on the new sensor and made a note of it. Then I replaced the sensor and let the other one cool to room temperature over the course of a day and measured its ohms and again at 32F (0C) using cold ice-water (Similar to how you calibrate a kitchen probe thermometer). There was a difference of 61 ohms between the two temperatures so clearly something is a miss in the old one seeing as the new one fixed the problem.
It was also a problem with the coolant reading 200F or more with the old one in place so the ohms could be drastically different between the two sensors at this temperature than just the 61 I could see at the cooler temperatures.
I waited a few days to be sure the problem wouldn't return because of the adaptives re-calibrating things and it hasn't. I went through a complete tank of gas in this time as well.
I'm posting here because I forget who else said they had a minor stumble as well in their 2018 PentaStar equipped vehicle. (My apologies I didn't make a note), and also for anyone else that might encounter the problem.
It now idles in gear and out of gear as smooth as glass and you can barely tell the vehicle is running at the lights it's so smooth and quiet. If it weren't for the injectors pulsing it would be hard to hear the engine at all with the hood closed.Changes I noticed
-Secondary ignition wave form looks slightly different from previous.
-Injector Pulse width has changed slightly under fully warmed up conditions compared to previous.
-The timing has changed ~2 degrees under various conditions verified with my dad's equipment and my scan-gauge.
-The temperature gauge doesn't bounce around as much when coasting down the highway as it did before.
-Long Term and Short Term Fuel trim numbers under various conditions as reported by my ScanGauge have changed from their previous numbers.
-During moderate acceleration it feels as though the engine pulls away better almost like it want's to go faster on its own ever so slightly. (Sorry best way I can describe it)
The sensor that came out was an Standard brand sensor and the one that went it was the same Standard brand. Only difference is that the one that went in didn't have the Mopar number stamped on the collar of the electrical connector.How to change the sensor the easy way
I changed the sensor quite easily while the coolant was warm. (It's located in the front head (Bank 2) in the Caravan on the right side, facing the radiator fan brass in colour with a 2 wire connector).
I took the upper radiator hose off the radiator and tied it to the crankcase fresh air breather line to keep it out of the way. (You don't need to remove the plastic clip holding it to the plennum)
I then took off the overflow bottle which just sits in slots on the radiator by sliding it upward. (Have to take off the hose going to the fill-neck of the radiator first though)
I Then slid the red safety lock on the sensors electrical connector backward using a small flat screw driver the length of my thumb, before squeezing and pulling off the connector.
Unscrewed the sensor using a 3/4" wrench and quickly put the other one in before too much coolant leaked out.
Tightened until just snug and then 1/2 turn to crush the sealing washer the sensor comes with.
I Put the connector back on and put the radiator hose / overflow bottle back in place. Topped up the coolant in the radiator and then somewhat burped the system running it without the cap on the radiator for a few minutes and then took it for a drive to continue the burping process.
Not that a coolant temperature sensor isn't important or doesn't play a big role in a vehicles engine management setup, but I think it's very important in the case of this engine because they run them as lean as possible for a PFI setup and even minor difference in readings between sensors that otherwise seem to function fine can make a big difference as noted above.
Anyway, happy it's fixed and happy to share with others that might be scouring the web for their 3.6L PentaStar Chrysler/Dodge engines in various models of vehicle.