Help me diagnose a stumble on a 3.8 - DodgeTalk : Dodge Car Forums, Dodge Truck Forums and Ram Forums
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#1 Old 08-28-2007, 02:47 PM
Rick99
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Help me diagnose a stumble on a 3.8

My wife's '01 T&C with the 3.8l v-6 has an occasional "stumble" or what seems like a miss during idle. It doesn't happen rythmically, but if you let it sit and idle long enough it will occasionally stumble hard enough to shake the van-- not back and forth, but just one thump, then it just continues idling smoothly until the next time. This seems to happen whether the engine is cool or warm-- at home after starting it in the morning or at a stop light after driving for a while. Sometimes, but not always, it will happen when accelerating from a stoplight.

Oh, I should add that once in a blue moon-- not often enough to even be annoying, the van will be very hard to start-- it will crank, but not start for several attempts. Don't know if that's related, but I thought I'd throw it out there.

The plugs and ignition wires were old enough that I just replaced them rather than test them and the problem did not go away. The PCV valve is fine too. Also, there are no PCM codes-- none stored, none pending.

So any ideas on what I should check next?

2003 Durango SLT
AWD, 4.7l
Mods: Remote Start
Just got a new set of BFG All-Terrains
Planning retrofit to 4WABS

1999 Durango SLT+
4x4, 5.2l
Mods: B&M Supercooler, Ford OEM Remote Start/Keyless Entry/Alarm, Heated Seats

01 T&C Limited 3.8l
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#2 Old 08-28-2007, 04:25 PM
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Throttle body/Throttle positioning sensor? Ever notice any RPM jumps while in cruise? I had something similar happen to another Chrysler product. Cleaned the throttle body and replaced the TPS. Worked like a dream.
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#3 Old 08-28-2007, 04:53 PM
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Is it possibly the air conditioning clutch cycling?
My $.02
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#4 Old 08-28-2007, 05:12 PM
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Thanks for the thoughts. It's definately not the A/C clutch cycling. The TPS is a thought-- could that cause a miss/stumble at idle though? This is happening only when you aren't pushing the throttle at all.

2003 Durango SLT
AWD, 4.7l
Mods: Remote Start
Just got a new set of BFG All-Terrains
Planning retrofit to 4WABS

1999 Durango SLT+
4x4, 5.2l
Mods: B&M Supercooler, Ford OEM Remote Start/Keyless Entry/Alarm, Heated Seats

01 T&C Limited 3.8l
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#5 Old 08-28-2007, 07:34 PM
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I think it could cause it. Does it idle perfectly smoothly otherwise. Does it hunt around at all?

How about the map or maf (I don't know which it has). Possibly need cleaning/replacement? Crank position sensor? If the crank is walking at all it could cause it to stumble.
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#6 Old 08-28-2007, 08:14 PM
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I hadn't really noticed if it was hunting, so I went outside to give it a test. I used the scan tool to watch RPM rather than just watching the tach. The van was cooperating with me a bit as it was missing constantly as I was testing it and the RPM was fluctuating from about 800 to 680. That was after letting it run a couple minutes to stabilize.

I also checked out the TPS voltage readings and with the engine off, it seems to move smoothly from .78 volts to about 3.88 volts. I think that's in spec as far as the voltage ranges, but the strange thing is that the scan tool is reporting TPS % at only 85% with full throttle. I checked it by pushing the throttle lever under the hood with the same result, so no linkage problem.

The TPS seems to fluctuate about .02 volts with the stumble and the MAP about .10 volts. Not sure if that's significant.

So does anyone know how I can test some of this stuff out without just replacing parts?

2003 Durango SLT
AWD, 4.7l
Mods: Remote Start
Just got a new set of BFG All-Terrains
Planning retrofit to 4WABS

1999 Durango SLT+
4x4, 5.2l
Mods: B&M Supercooler, Ford OEM Remote Start/Keyless Entry/Alarm, Heated Seats

01 T&C Limited 3.8l
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#7 Old 08-29-2007, 10:59 AM
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my '98 has the same problem and it happens under just about all driving conditions. cold, warm, idling, highway speeds. it happens when the a/c cuts in and its like a hard bump when it does

there is a TSB on this issue that reprograms the PCM to dump a bit more fuel into the engine to allow the engine to absorb some of the bump when the compressor cuts in

but take note that the A/C WILL cycle in the defrost or defrost/floor setting no matter if the snowflake button is on or off

2005 Chrysler 300 (DD): 6000K 50W HIDs, Niteshades, LED Interior light Conversion...
'99 Caravan: Work van. 6000K HID headlights and fogs
'92 Chrysler Daytona IROC R/T (2.2L DOHC Turbo-III)
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#8 Old 08-29-2007, 12:31 PM
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The PCM supplies approximately 5 volts to the TPS. The TPS output voltage (input signal to the powertrain control module) represents throttle blade position. The TPS output voltage to the PCM varies from approximately 0.6 volt at minimum throttle opening (idle) to a maximum of 4.5 volts at wide open throttle.

Along with inputs from other sensors, the PCM uses the TPS input to determine current engine operating conditions. The PCM also adjusts fuel injector pulse width and ignition timing based on these inputs.

Also like the cam and crank sensors, a 5 volt reference is supplied from the PCM and returns a voltage signal to the PCM that reflects manifold pressure. The zero pressure reading is 0.5V and full scale is 4.5V . For a pressure swing of 0 - 15 psi the voltage changes 4.0V . The sensor is supplied a regulated 4.8 to 5.1 volts to operate the sensor. Like the cam and crank sensors ground is provided through the sensor return circuit.
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#9 Old 08-29-2007, 01:04 PM
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Donald-- Good thought-- I just flashed the PCM and the TCM up to the latest software two weeks ago and unfortunately, it didn't fix the problem.

XDGT03-- Thanks for the info on the TPS and MAP sensor. I think I read some factory materials that showed 0.78 volts at closed and 3.88 volts at WOT was within spec, but the fact that it should be as high as 4.5volts and that the PCM is reading it as only 85% makes me think that spec is off and something is wrong with the TPS in any case. I may replace that, since it seems to be messed up whether it is causing this problem or not. When I'm in there, I'll see if the throttle body and IAC are dirty.

Does anyone know what the MAP should be reading at idle? Maybe that's a way to test it.

2003 Durango SLT
AWD, 4.7l
Mods: Remote Start
Just got a new set of BFG All-Terrains
Planning retrofit to 4WABS

1999 Durango SLT+
4x4, 5.2l
Mods: B&M Supercooler, Ford OEM Remote Start/Keyless Entry/Alarm, Heated Seats

01 T&C Limited 3.8l
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#10 Old 08-29-2007, 08:00 PM
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Well, I think you would actually want to monitor it at the stumble to see if its reading varies prior to or after it. My guess would be something around 1.5 v at idle.
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#11 Old 08-29-2007, 09:07 PM
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miss

Could be a flakey or partially gummed up egr valve even if it doesn't throw a code .
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#12 Old 08-30-2007, 10:36 AM
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Quote:
Originally Posted by vipergg
Could be a flakey or partially gummed up egr valve even if it doesn't throw a code .

I'm going to have to take back some of the information I provided above. Last night I took off the EGR valve and it did have plenty of carbon in it but seemed to be opening and closing smoothly with a vacuum pump. I cleaned it up a bit anyway and put it back on. When I started the engine and let it idle it was smooth as silk-- great right?

Well, I realized the A/C was off and tried turning it on. With the A/C on, the stumble came back. The strange thing is that the stumble does not happen at the time that the A/C compressor engages or disengages (I can hear the click and watch it on my scan tool), which is why I said this wasn't related, but it definately happens while the A/C compressor is already engaged and it does not appear to happen when the A/C is off. I may run it a little more to verify this, but it seems to be what's going on.

2003 Durango SLT
AWD, 4.7l
Mods: Remote Start
Just got a new set of BFG All-Terrains
Planning retrofit to 4WABS

1999 Durango SLT+
4x4, 5.2l
Mods: B&M Supercooler, Ford OEM Remote Start/Keyless Entry/Alarm, Heated Seats

01 T&C Limited 3.8l

Last edited by Rick99; 08-30-2007 at 10:51 AM.
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#13 Old 08-30-2007, 10:49 AM
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IAC motor maybe? the PCM will open it up some at the same time as the A/C compressor to take up the extra load that the compressor puts on the engine

2005 Chrysler 300 (DD): 6000K 50W HIDs, Niteshades, LED Interior light Conversion...
'99 Caravan: Work van. 6000K HID headlights and fogs
'92 Chrysler Daytona IROC R/T (2.2L DOHC Turbo-III)
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#14 Old 08-30-2007, 08:06 PM
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Im having the same problem with my 99 3.8 caravan. This thread was helpful. Thanks
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#15 Old 08-31-2007, 06:19 AM
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Quote:
Originally Posted by STEAMFITTER
Im having the same problem with my 99 3.8 caravan. This thread was helpful. Thanks

Yes, it's been helpful for me too-- just to think through what may be causing this-- so thanks to all that are responding. My next step is to clean up the TB and IAC and I'll report back with results.

2003 Durango SLT
AWD, 4.7l
Mods: Remote Start
Just got a new set of BFG All-Terrains
Planning retrofit to 4WABS

1999 Durango SLT+
4x4, 5.2l
Mods: B&M Supercooler, Ford OEM Remote Start/Keyless Entry/Alarm, Heated Seats

01 T&C Limited 3.8l
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#16 Old 08-31-2007, 06:21 PM
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I found this TSB

NUMBER: 18-008-02

GROUP: Vehicle Performance

DATE: Feb. 11, 2002

THIS BULLETIN SUPERSEDES TECHNICAL SERVICE BULLETIN 18-008-01, DATED MARCH 16, 2001, WHICH SHOULD BE REMOVED FROM YOUR FILES. ALL REVISIONS ARE HIGHLIGHTED WITH **ASTERISKS** AND INCLUDE ADDITIONAL MODELS.
SUBJECT:
Engine Sag/Hesitation And/Or Closed Throttle Start Stall

OVERVIEW:
This bulletin involves replacing the Throttle Position Sensor (TPS).

MODELS:

2001 - **2002** (RS) Caravan/Voyager/Town & Country

2001 - **2002** (RG) Chrysler Voyager (International Market)
NOTE :**THIS BULLETIN APPLIES TO VEHICLES EQUIPPED WITH A 3.3L OR 3.8L ENGINE AND BUILT BEFORE OCTOBER 01, 2001 (MDH 1001XX).**

SYMPTOM/CONDITION:

Engine hesitation/sag, closed throttle start/stall, and/or Diagnostic Trouble Code (DTC) P0123 - "Throttle Position Sensor Voltage High". May be more prevalent in cold temperatures below 0C. (32F).

DIAGNOSIS:

If no DTC's are present or DTC P0123 is present, perform the Repair Procedure.

If other DTC's are present further diagnosis is required.



PARTS REQUIRED:

REPAIR PROCEDURE:
1. Disconnect the negative battery cable.

2. Remove the electrical connector from the Inlet Air Temperature Sensor.

3. Remove the air cleaner box lid. Remove hose from throttle body.

4. Disconnect the electrical connector at the TPS.

5. Disconnect the electrical connector at the Idle Air Control (IAC).

6. Remove the three (3) TPS mounting bolts and TPS.

7. Reverse the previous steps to install new TPS, p/n 04686360.

POLICY:
Reimbursable within the provisions of the warranty.
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#17 Old 08-31-2007, 09:05 PM
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Hey, nice find! I guess I will replace the TPS as well as cleaning the IAC then.

2003 Durango SLT
AWD, 4.7l
Mods: Remote Start
Just got a new set of BFG All-Terrains
Planning retrofit to 4WABS

1999 Durango SLT+
4x4, 5.2l
Mods: B&M Supercooler, Ford OEM Remote Start/Keyless Entry/Alarm, Heated Seats

01 T&C Limited 3.8l
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#18 Old 09-04-2007, 06:23 PM
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Post #16
I found this TSB

NUMBER: 18-008-02

GROUP: Vehicle Performance

DATE: Feb. 11, 2002

THIS BULLETIN SUPERSEDES TECHNICAL SERVICE BULLETIN 18-008-01, DATED MARCH 16, 2001, WHICH SHOULD BE REMOVED FROM YOUR FILES. ALL REVISIONS ARE HIGHLIGHTED WITH **ASTERISKS** AND INCLUDE ADDITIONAL MODELS.
SUBJECT:
Engine Sag/Hesitation And/Or Closed Throttle Start Stall

OVERVIEW:
This bulletin involves replacing the Throttle Position Sensor (TPS).

MODELS:

2001 - **2002** (RS) Caravan/Voyager/Town & Country

2001 - **2002** (RG) Chrysler Voyager (International Market)
NOTE :**THIS BULLETIN APPLIES TO VEHICLES EQUIPPED WITH A 3.3L OR 3.8L ENGINE AND BUILT BEFORE OCTOBER 01, 2001 (MDH 1001XX).**

SYMPTOM/CONDITION:

Engine hesitation/sag, closed throttle start/stall, and/or Diagnostic Trouble Code (DTC) P0123 - "Throttle Position Sensor Voltage High". May be more prevalent in cold temperatures below 0C. (32F).

DIAGNOSIS:

If no DTC's are present or DTC P0123 is present, perform the Repair Procedure.

If other DTC's are present further diagnosis is required.



PARTS REQUIRED:

REPAIR PROCEDURE:
1. Disconnect the negative battery cable.

2. Remove the electrical connector from the Inlet Air Temperature Sensor.

3. Remove the air cleaner box lid. Remove hose from throttle body.

4. Disconnect the electrical connector at the TPS.

5. Disconnect the electrical connector at the Idle Air Control (IAC).

6. Remove the three (3) TPS mounting bolts and TPS.

7. Reverse the previous steps to install new TPS, p/n 04686360.

POLICY:
Reimbursable within the provisions of the warranty.
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#19 Old 09-04-2007, 06:25 PM
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Thanks to the person who sent this to me. Much appreciated.
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#20 Old 10-13-2007, 04:47 PM
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this did not work for me. ill try a reset
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