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PentaStar Hot Stumble - Fixed #4973413
01/08/19 05:07 PM
01/08/19 05:07 PM
Joined: Aug 2008
Posts: 24,091
ON, Canada eh?
StevieC Offline OP
StevieC  Offline OP

Joined: Aug 2008
Posts: 24,091
ON, Canada eh?
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.

cheers

Last edited by StevieC; 01/08/19 05:19 PM.

'18 Dodge Grand Caravan GT - 25k KM - AMSOIL SS 0w20

Fear 20wt oils if you want your engine to last. smirk2
Re: PentaStar Hot Stumble - Fixed [Re: StevieC] #4973440
01/08/19 05:53 PM
01/08/19 05:53 PM
Joined: Nov 2004
Posts: 1,915
SD
zrxkawboy Offline
zrxkawboy  Offline

Joined: Nov 2004
Posts: 1,915
SD
Thanks for the tip. Good job on fixing the problem!


"Think of all the Ford owners who will someday want an automobile." John Dodge

Re: PentaStar Hot Stumble - Fixed [Re: zrxkawboy] #4973446
01/08/19 05:58 PM
01/08/19 05:58 PM
Joined: Aug 2008
Posts: 24,091
ON, Canada eh?
StevieC Offline OP
StevieC  Offline OP

Joined: Aug 2008
Posts: 24,091
ON, Canada eh?
Originally Posted by zrxkawboy
Thanks for the tip. Good job on fixing the problem!

thumbsup You are welcome...

Last edited by StevieC; 01/08/19 05:59 PM.

'18 Dodge Grand Caravan GT - 25k KM - AMSOIL SS 0w20

Fear 20wt oils if you want your engine to last. smirk2
Re: PentaStar Hot Stumble - Fixed [Re: StevieC] #4973453
01/08/19 06:09 PM
01/08/19 06:09 PM
Joined: Nov 2018
Posts: 455
Chicagoland
Skippy722 Online content
Skippy722  Online Content

Joined: Nov 2018
Posts: 455
Chicagoland
Good too know! I’ll lkeep this in mind if mine ever starts acting up.

The Grand Caravan doesn’t use the PUG engine does it? Or did they finally update that?


2016 Chrysler 300S v6
2018 Dodge Grand Caravan GT

Slight Mopar obsession
Re: PentaStar Hot Stumble - Fixed [Re: StevieC] #4973460
01/08/19 06:13 PM
01/08/19 06:13 PM
Joined: Apr 2018
Posts: 479
south dakota
joekingcorvette Offline
joekingcorvette  Offline

Joined: Apr 2018
Posts: 479
south dakota
Good to know thanks for the tip!


2005 Chevrolet Corvette
2014 Ford F-150 4x4 supercrew
2014 Jeep Grand Cherokee Limited (wifes)
2012 Honda Civic 4 door (my daily driver)
2007 Lund Tyee Grand Sport Mercury 115HP 9.8HP
Re: PentaStar Hot Stumble - Fixed [Re: StevieC] #4973470
01/08/19 06:21 PM
01/08/19 06:21 PM
Joined: Dec 2002
Posts: 42,513
'Stralia
Shannow Offline
Shannow  Offline

Joined: Dec 2002
Posts: 42,513
'Stralia
Didn't ethanol blends fix it ?


Because sometimes the simple things in life...
...simply don't know any better
Re: PentaStar Hot Stumble - Fixed [Re: Shannow] #4973536
01/08/19 07:51 PM
01/08/19 07:51 PM
Joined: Aug 2008
Posts: 24,091
ON, Canada eh?
StevieC Offline OP
StevieC  Offline OP

Joined: Aug 2008
Posts: 24,091
ON, Canada eh?
Originally Posted by Shannow
Didn't ethanol blends fix it ?

I thought so originally and then it came back. It was weird though because it only came back on 91 E-0 it appeared but as time went on it appeared with the 87 E-10 so it was just a fluke. I posted that in that thread.


'18 Dodge Grand Caravan GT - 25k KM - AMSOIL SS 0w20

Fear 20wt oils if you want your engine to last. smirk2
Re: PentaStar Hot Stumble - Fixed [Re: Skippy722] #4973537
01/08/19 07:53 PM
01/08/19 07:53 PM
Joined: Aug 2008
Posts: 24,091
ON, Canada eh?
StevieC Offline OP
StevieC  Offline OP

Joined: Aug 2008
Posts: 24,091
ON, Canada eh?
Originally Posted by Skippy722
Good too know! I’ll lkeep this in mind if mine ever starts acting up.

The Grand Caravan doesn’t use the PUG engine does it? Or did they finally update that?

The GC's only use the PentaStar until their discontinuation at the end of 2019. The Pacifica vans also use the PentaStar but with a 9-Speed transmission instead of the 6-speed in the Caravan. Ram 1500's use it is used in the Jeep line as well. Waiting on the new straight six coming. slobber That will be my next vehicle if it turns out to be a winner like the PentaStar.

I think the 6-speed 62TE and the PentaStar is a great match and really enjoy my commute in it daily.

Now that I have that squared away and I found 1/2" Fuel line I'm going to put my Catch Can that I had on the Highlander on this and see what it catches. Just for fun, not because I think it needs it. Although the line from the PCV on the rear camshaft to the plennum is like 8" at best so it might catch some stuff diverting it to the can first. (Can't stop tinkering).

Last edited by StevieC; 01/08/19 07:56 PM.

'18 Dodge Grand Caravan GT - 25k KM - AMSOIL SS 0w20

Fear 20wt oils if you want your engine to last. smirk2
Re: PentaStar Hot Stumble - Fixed [Re: StevieC] #4973543
01/08/19 07:59 PM
01/08/19 07:59 PM
Joined: Mar 2016
Posts: 1,719
Toronto
PeterPolyol Offline
PeterPolyol  Offline

Joined: Mar 2016
Posts: 1,719
Toronto
Good thing it wasn't misbehaving that badly and good job IDing it. My old Camry use to stall the engine out and not start up again from a bad ECTS giving wild and erratic readings. Never once tripped a CEL which made diagnosis a real bear


There's no replacement...'scosity for natural viscosity
Re: PentaStar Hot Stumble - Fixed [Re: StevieC] #4973550
01/08/19 08:05 PM
01/08/19 08:05 PM
Joined: Dec 2013
Posts: 2,838
Fort Worth, Texas
clinebarger Offline
clinebarger  Offline

Joined: Dec 2013
Posts: 2,838
Fort Worth, Texas
How did you obtain a Secondary Waveform on a COP Coil?
In my experience.....I've never seen much difference in secondary waveforms if the ignition components & engine is in good health.........Unless it's running so lean that the engine is actively misfiring.

I find it easier to tag Primary Current on Ford & Chrysler COP vehicles as the Transistor is remote (PCM).


2001 Chevy Camaro L92/4L80E
2006 Chevy 2500HD LBZ/Allison 1000
2010 Toyota Corolla 2ZR-FE/U341E
2000 Toyota Avalon 1MZ-FE/A541E
Re: PentaStar Hot Stumble - Fixed [Re: StevieC] #4973613
01/08/19 08:54 PM
01/08/19 08:54 PM
Joined: Aug 2008
Posts: 24,091
ON, Canada eh?
StevieC Offline OP
StevieC  Offline OP

Joined: Aug 2008
Posts: 24,091
ON, Canada eh?
My dad has a pick-up that goes between the boot and the coil over and another going after the boot to the plug. Pico does a good job explaining how it works although his isn't a Pico. I would love to have a Pico though. slobber https://www.picoauto.com/library/automotive-guided-tests/secondary-coil-output-test/

It's a royal pain in the you know where to do this on the PentaStar with the plennum needing to be removed and then trying to fit all this mess with the coils underneath it while testing as the plennum has to be back on for the test. We ended up doing 1 cylinder at a time and just using 2 of the bolts to hold the plennum in place in between testing the front cylinders.

Back cylinders are easy because it just involves removing the throttle body and air tubing/box at the back to change from one cylinder to the next.

I have access to his big arse garage at his rural home and it's semi-heated and there is always fresh coffee mum makes so I have all the time in the world to mess around. Like a kid in a candy store plus I get to spend time with my dad before the inevitable happens.

Last edited by StevieC; 01/08/19 09:08 PM.

'18 Dodge Grand Caravan GT - 25k KM - AMSOIL SS 0w20

Fear 20wt oils if you want your engine to last. smirk2
Re: PentaStar Hot Stumble - Fixed [Re: StevieC] #4973619
01/08/19 08:57 PM
01/08/19 08:57 PM
Joined: Dec 2006
Posts: 8,362
Canuck living in California
KrisZ Offline
KrisZ  Offline

Joined: Dec 2006
Posts: 8,362
Canuck living in California
Nice diagnostics and fix, will file this just in case I need it. Thanks for sharing this thumbsup


2015 Grand Caravan 3.6L - 31k miles.
2006 Mazda 3 2.0L - 171k miles
Re: PentaStar Hot Stumble - Fixed [Re: KrisZ] #4973625
01/08/19 09:01 PM
01/08/19 09:01 PM
Joined: Aug 2008
Posts: 24,091
ON, Canada eh?
StevieC Offline OP
StevieC  Offline OP

Joined: Aug 2008
Posts: 24,091
ON, Canada eh?
Originally Posted by KrisZ
Nice diagnostics and fix, will file this just in case I need it. Thanks for sharing this thumbsup

Glad folks might get use out of this. It was a weird one because it wouldn't set the misfire counter on the cylinders either and no MIL/CEL.


'18 Dodge Grand Caravan GT - 25k KM - AMSOIL SS 0w20

Fear 20wt oils if you want your engine to last. smirk2
Re: PentaStar Hot Stumble - Fixed [Re: StevieC] #4973698
01/08/19 10:15 PM
01/08/19 10:15 PM
Joined: Aug 2017
Posts: 797
MN
14Accent Offline
14Accent  Offline

Joined: Aug 2017
Posts: 797
MN
Great diagnosis! Just goes to show how reliant engine computers are on coolant temperature readings for proper operation.

Reminds me of a tough one I had come through the shop earlier this week. 1994 Econoline with the 4.9 straight 6. The complaint was a surging and stalling when up to temp, coming to a stop or taking off from a light.

I could tell right away on my test drive that something wasn't right. It's idled OK, cruised OK, but throttle tip-in was awful. It wanted to stall almost every time. Being OBD1, I figured I had a long road ahead of me.

Long story short, a quick scan of the limited data stream showed an engine coolant temp of 400!! I almost couldn't believe it. I tested the wiring to confirm the PCM was alright, and replaced the sensor. It solved all the problems!


2013 Chevrolet Volt - Saves enough in fuel to pay for itself!

2003 Cadillac Seville STS - The winter "beater", it uses the Volt's fuel
Re: PentaStar Hot Stumble - Fixed [Re: StevieC] #4973700
01/08/19 10:17 PM
01/08/19 10:17 PM
Joined: Aug 2008
Posts: 24,091
ON, Canada eh?
StevieC Offline OP
StevieC  Offline OP

Joined: Aug 2008
Posts: 24,091
ON, Canada eh?
400, wow. LOL


'18 Dodge Grand Caravan GT - 25k KM - AMSOIL SS 0w20

Fear 20wt oils if you want your engine to last. smirk2
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