Truck occasionally dies when stopping
#41
07-21-2011 | 04:01 PM
Registered User
Joined: Jul 2011
Posts: 12
Likes: 0
2001 Dodge Dakota 4.7 V8 QUAD Cab *Updated 5/25/2011*
This started happening about a 6 months ago where the engine will occasionally die when stopping at a red light or at a stop sign. Sometimes it feels like stopping on an incline causes it to die more but it does die even on flat ground.
Here are my symptoms:
Here's what I've done to try and fix the issue to no avail:
What to do next?
Replaced the IAC sensor, there is def. improvement however the idle does still dip when going in reverse or stopping.
*Update 5/31/2011*
Replaced the TPS. Sadly zero improvement.
This started happening about a 6 months ago where the engine will occasionally die when stopping at a red light or at a stop sign. Sometimes it feels like stopping on an incline causes it to die more but it does die even on flat ground.
Here are my symptoms:
- Dies while stopping
- RPM tries to fight but ends up dead
- RPM struggles when AC is on
- Truck is shifting hard both up and down *updated 7/18/2011
- RPM struggles a tiny bit when using power steering
- Truck dies sometimes when going from drive to reverse
- Truck starts back up easily every time
- MPG on my truck seems pretty bad at 12MPG
- RPM idles at a tad bit above 500.
- Battery is less than 6 months old. *updated 5/25/2011
Here's what I've done to try and fix the issue to no avail:
- Replaced Spark Plugs
- Replaced Spark Wires
- Cleared air filter
- Reset truck computer (unplug battery)
- Put Seafoam in gas tank *updated 5/11/2011
- Replaced IAC *updated 5/25/2011
- Replace the TPS sensor *updated 5/31/2011
What to do next?
- Go to dealer and get new PCM firmware
Replaced the IAC sensor, there is def. improvement however the idle does still dip when going in reverse or stopping.
*Update 5/31/2011*
Replaced the TPS. Sadly zero improvement.
The truck would start ok and idle, and as soon as I put it in Drive and started to roll
and apply the brakes, the rpms on the tach would drop down to 0 and the engine would stall.
Started ok and would idle but again same thing as soon as it started to
move and stop. Turned out to be a bad aftermarket sensor (2.5 v on
closed throttle and 4.75 volt on fully open).
I ended up putting the original TPS sensor back on and measuring it's o/p with a DVM.
Positve lead of DVM to center wire on the TPS 3 wire plug.
(you will need to push the point of the probe into the insulation),
the neg probe to a good engine ground.
*Turn the key on but do not start the engine.*
Measure the TPS voltage with the throttle body closed (you will need to take the air hose off to see this),
then slowly open the throttle by hand all the way up to full opening, and note DVM voltage reading.
The sensor if working should go from around 0.5 v (closed throttle) to 4.5 v full throttle.
(mine read 0.66v (closed) and 3.77 fully open. It was still good.
NOTE: Ignition key on but dont start engine..just operate throttle by hand.
My original TPS is back l on and works ok now, now that I found the
real reason for the hard shifts.
Anyway, the reason I replaced the TPS in the first place was because of
hard shift symptom (engine would rev up to 3500 during 1-2 and 2-3rd.
These are hard shifts because the fluid build up more pressure at those
rpms and forces the shift, rather than the PCM making a shift point determination
at a lower rpm (typically 1800 to 2200rpm).
Some users stated that replacing the TPS helped, but in my case
with a defective replacement TPS sensor, it threw me off.
I had to put the original back..fortunately today... the PCM finally provided
a clue with a check engine lite that my code reader indicated was a P-720
(VSS) Vehicle speed sensor (in my 47re transmission) was too low.
I had that replaced today, now the hard shifts are gone.
I've had this problem for a couple months now, and being intermittent,
it made it harder to troubleshoot.
With the VSS replaced today..tranny is shifting just like it used to.
I would suspect that your poor gas mileage is because the engine
is revving at higher rpms consuming more gas before shifting.
I would concentrate on:
1) double checking the voltage o/p on your replacement TPS
to make sure it is working within the range that the PCM
expects.
2) Are you sure that the IAC (idle air control) is working properly?
This is driven by the PCM to adjust the air during idle on when
the engine is experiencing some load like the (A/C on) or wheels turned
and engine is driving the power steering pump more.
3. Also you might consider changing the VSS on the transmission
I never toss the original sensors until I am sure they are defective, because
sometimes even the new ones may not be 100%.
Last edited by carverman; 07-21-2011 at 04:33 PM.
#42
07-22-2011 | 01:55 PM
Thread Starter
|
Amateur
Joined: Mar 2009
Posts: 36
Likes: 0
I had the same problem with a defective NEW replacement TPS sensor.
The truck would start ok and idle, and as soon as I put it in Drive and started to roll
and apply the brakes, the rpms on the tach would drop down to 0 and the engine would stall.
Started ok and would idle but again same thing as soon as it started to
move and stop. Turned out to be a bad aftermarket sensor (2.5 v on
closed throttle and 4.75 volt on fully open).
I ended up putting the original TPS sensor back on and measuring it's o/p with a DVM.
Positve lead of DVM to center wire on the TPS 3 wire plug.
(you will need to push the point of the probe into the insulation),
the neg probe to a good engine ground.
*Turn the key on but do not start the engine.*
Measure the TPS voltage with the throttle body closed (you will need to take the air hose off to see this),
then slowly open the throttle by hand all the way up to full opening, and note DVM voltage reading.
The sensor if working should go from around 0.5 v (closed throttle) to 4.5 v full throttle.
(mine read 0.66v (closed) and 3.77 fully open. It was still good.
NOTE: Ignition key on but dont start engine..just operate throttle by hand.
My original TPS is back l on and works ok now, now that I found the
real reason for the hard shifts.
Anyway, the reason I replaced the TPS in the first place was because of
hard shift symptom (engine would rev up to 3500 during 1-2 and 2-3rd.
These are hard shifts because the fluid build up more pressure at those
rpms and forces the shift, rather than the PCM making a shift point determination
at a lower rpm (typically 1800 to 2200rpm).
Some users stated that replacing the TPS helped, but in my case
with a defective replacement TPS sensor, it threw me off.
I had to put the original back..fortunately today... the PCM finally provided
a clue with a check engine lite that my code reader indicated was a P-720
(VSS) Vehicle speed sensor (in my 47re transmission) was too low.
I had that replaced today, now the hard shifts are gone.
I've had this problem for a couple months now, and being intermittent,
it made it harder to troubleshoot.
With the VSS replaced today..tranny is shifting just like it used to.
I would suspect that your poor gas mileage is because the engine
is revving at higher rpms consuming more gas before shifting.
I would concentrate on:
1) double checking the voltage o/p on your replacement TPS
to make sure it is working within the range that the PCM
expects.
2) Are you sure that the IAC (idle air control) is working properly?
This is driven by the PCM to adjust the air during idle on when
the engine is experiencing some load like the (A/C on) or wheels turned
and engine is driving the power steering pump more.
3. Also you might consider changing the VSS on the transmission
I never toss the original sensors until I am sure they are defective, because
sometimes even the new ones may not be 100%.
The truck would start ok and idle, and as soon as I put it in Drive and started to roll
and apply the brakes, the rpms on the tach would drop down to 0 and the engine would stall.
Started ok and would idle but again same thing as soon as it started to
move and stop. Turned out to be a bad aftermarket sensor (2.5 v on
closed throttle and 4.75 volt on fully open).
I ended up putting the original TPS sensor back on and measuring it's o/p with a DVM.
Positve lead of DVM to center wire on the TPS 3 wire plug.
(you will need to push the point of the probe into the insulation),
the neg probe to a good engine ground.
*Turn the key on but do not start the engine.*
Measure the TPS voltage with the throttle body closed (you will need to take the air hose off to see this),
then slowly open the throttle by hand all the way up to full opening, and note DVM voltage reading.
The sensor if working should go from around 0.5 v (closed throttle) to 4.5 v full throttle.
(mine read 0.66v (closed) and 3.77 fully open. It was still good.
NOTE: Ignition key on but dont start engine..just operate throttle by hand.
My original TPS is back l on and works ok now, now that I found the
real reason for the hard shifts.
Anyway, the reason I replaced the TPS in the first place was because of
hard shift symptom (engine would rev up to 3500 during 1-2 and 2-3rd.
These are hard shifts because the fluid build up more pressure at those
rpms and forces the shift, rather than the PCM making a shift point determination
at a lower rpm (typically 1800 to 2200rpm).
Some users stated that replacing the TPS helped, but in my case
with a defective replacement TPS sensor, it threw me off.
I had to put the original back..fortunately today... the PCM finally provided
a clue with a check engine lite that my code reader indicated was a P-720
(VSS) Vehicle speed sensor (in my 47re transmission) was too low.
I had that replaced today, now the hard shifts are gone.
I've had this problem for a couple months now, and being intermittent,
it made it harder to troubleshoot.
With the VSS replaced today..tranny is shifting just like it used to.
I would suspect that your poor gas mileage is because the engine
is revving at higher rpms consuming more gas before shifting.
I would concentrate on:
1) double checking the voltage o/p on your replacement TPS
to make sure it is working within the range that the PCM
expects.
2) Are you sure that the IAC (idle air control) is working properly?
This is driven by the PCM to adjust the air during idle on when
the engine is experiencing some load like the (A/C on) or wheels turned
and engine is driving the power steering pump more.
3. Also you might consider changing the VSS on the transmission
I never toss the original sensors until I am sure they are defective, because
sometimes even the new ones may not be 100%.
I need to run to the pawn shop and buy something that can measure voltage for me. I'll also look up the VSS prices. 
#43
07-23-2011 | 04:17 PM
Registered User
Joined: Jul 2011
Posts: 12
Likes: 0
Ok, before we continue..you seem to have two problems with your truck.
Hard shifting on the transmission and poor fuel economy right?
The 46re or whichever model is in your truck is derived from the Chrysler
TORQUEFLITE transmission, these are some of the best transmissions out
there..but it has electronic sensors to allow the PCM (powertrain control
module) to determine pressure inside the shifter valve body that operates
the forward and reverse/overrunning clutch and the forward and reverse
bands. Fourth gear is overdrive and selected by the PCM at a certain
engine rpm and vehicle speed.
On my 98 dakota (and I've read a lot about these transmissions since
my shift problem developed), it has a pressure governor/shift valve that
is controlled by the PCM for optimal fuel saving shift parameters.
(These are learned by the PCM from your driving habits.)
IF the PCM can detect the tailshaft rpm (on the o/p of the transmission)
it can compute the optimum shift point for 1-2 and 2-3. Two sensors
play an important part the TPS and the TSS (Transmission speed sensor)
sometimes also called the VSS.
4th gear (overdrive) "shift" is only determined by the PCM through
the rpm of the engine/transmission sensors and whether the OD button
is on or disabled on the manual shifter stalk inside.
Normally the PCM will determine the shift points for you and you get
smooth shifts. If you see the RPMs climbing and the engine rpm
"hunting" or flare as it's called then you usually need to check those
two sensors, if there is no check engine light code.
You can troubleshoot most sensors with a DVM, as long as you have
instruction that tells you which wire to probe at the sensor and what
you expect to see in normal sensor range.
Fluid leakage is a sign of a transmission seal that may be leaking or
also rust pinhole spots on the transmission cooler lines.
The transmission fluid level on these "torqueflites" should always be
checked in NEUTRAL with the parking brake engaged and not in PARK.
The reason is that there is a difference in how the fluid is accumulated
in the lockup torque convertor on these transmissions. In PARK, there
is a partial fill and in Neutral..before you select D, there is a full fill
of the torque converter, so the dipstick reading should be done in
Neutral only.
Hard shifting on the transmission and poor fuel economy right?
The 46re or whichever model is in your truck is derived from the Chrysler
TORQUEFLITE transmission, these are some of the best transmissions out
there..but it has electronic sensors to allow the PCM (powertrain control
module) to determine pressure inside the shifter valve body that operates
the forward and reverse/overrunning clutch and the forward and reverse
bands. Fourth gear is overdrive and selected by the PCM at a certain
engine rpm and vehicle speed.
On my 98 dakota (and I've read a lot about these transmissions since
my shift problem developed), it has a pressure governor/shift valve that
is controlled by the PCM for optimal fuel saving shift parameters.
(These are learned by the PCM from your driving habits.)
IF the PCM can detect the tailshaft rpm (on the o/p of the transmission)
it can compute the optimum shift point for 1-2 and 2-3. Two sensors
play an important part the TPS and the TSS (Transmission speed sensor)
sometimes also called the VSS.
4th gear (overdrive) "shift" is only determined by the PCM through
the rpm of the engine/transmission sensors and whether the OD button
is on or disabled on the manual shifter stalk inside.
Normally the PCM will determine the shift points for you and you get
smooth shifts. If you see the RPMs climbing and the engine rpm
"hunting" or flare as it's called then you usually need to check those
two sensors, if there is no check engine light code.
You can troubleshoot most sensors with a DVM, as long as you have
instruction that tells you which wire to probe at the sensor and what
you expect to see in normal sensor range.
Fluid leakage is a sign of a transmission seal that may be leaking or
also rust pinhole spots on the transmission cooler lines.
The transmission fluid level on these "torqueflites" should always be
checked in NEUTRAL with the parking brake engaged and not in PARK.
The reason is that there is a difference in how the fluid is accumulated
in the lockup torque convertor on these transmissions. In PARK, there
is a partial fill and in Neutral..before you select D, there is a full fill
of the torque converter, so the dipstick reading should be done in
Neutral only.
#44
07-23-2011 | 04:30 PM
Registered User
Joined: Jul 2011
Posts: 12
Likes: 0
OMG Thank you so much for the in-depth write up. I still have the old IAC sensors and didn't think of even testing the new one I received from rockauto.com. I need to run to the pawn shop and buy something that can measure voltage for me. I'll also look up the VSS prices.
I need to run to the pawn shop and buy something that can measure voltage for me. I'll also look up the VSS prices. They generally are fairly reliable, but can get black soot on the end of the
air pointed end adjusting part of the motor.
Generally you just need to clean them..and I've cleaned mine and it
works just fine. It was not the cause of my idle problems.
The PCM operates the IAC to allow more air into the throttle body when
the engine rpm drops due to some extra load on the engine,
like turning on the a/c compressor or power steering pump pressure buildup.
It's a bit like the old idle (air) adjusting screws on the old carburator models,
but computer controlled of course.
here is a link to the description of how it works and how to clean it.
http://www.2carpros.com/articles/how...ol-valve-works
#45
07-23-2011 | 04:48 PM
Registered User
Joined: Jul 2011
Posts: 12
Likes: 0
One thing I forgot to mention on the second generation dakotas is something called the ASD relay
in the PDC (power distribution center) in the engine compartment.
It has fuses and relays.
On the inside of the cover, are the locations and designations of the relays and fuses.
The ASD (Auto Shutdown Relay), if operated by the PCM will kill the ignition
coil and the fuel injectors, if the PCM detects a "certain type" of sensor
problem or a fuel delivery (fuel pump )issue. Not sure this seems like
a possible cause for your problem because of the hard shifts you are experiencing.
in the PDC (power distribution center) in the engine compartment.
It has fuses and relays.
On the inside of the cover, are the locations and designations of the relays and fuses.
The ASD (Auto Shutdown Relay), if operated by the PCM will kill the ignition
coil and the fuel injectors, if the PCM detects a "certain type" of sensor
problem or a fuel delivery (fuel pump )issue. Not sure this seems like
a possible cause for your problem because of the hard shifts you are experiencing.
Last edited by carverman; 07-23-2011 at 04:50 PM.
#47
02-15-2013 | 10:37 PM
Thread Starter
|
Amateur
Joined: Mar 2009
Posts: 36
Likes: 0
I had the same problem with a defective NEW replacement TPS sensor.
The truck would start ok and idle, and as soon as I put it in Drive and started to roll
and apply the brakes, the rpms on the tach would drop down to 0 and the engine would stall.
Started ok and would idle but again same thing as soon as it started to
move and stop. Turned out to be a bad aftermarket sensor (2.5 v on
closed throttle and 4.75 volt on fully open).
I ended up putting the original TPS sensor back on and measuring it's o/p with a DVM.
Positve lead of DVM to center wire on the TPS 3 wire plug.
(you will need to push the point of the probe into the insulation),
the neg probe to a good engine ground.
*Turn the key on but do not start the engine.*
Measure the TPS voltage with the throttle body closed (you will need to take the air hose off to see this),
then slowly open the throttle by hand all the way up to full opening, and note DVM voltage reading.
The sensor if working should go from around 0.5 v (closed throttle) to 4.5 v full throttle.
(mine read 0.66v (closed) and 3.77 fully open. It was still good.
NOTE: Ignition key on but dont start engine..just operate throttle by hand.
My original TPS is back l on and works ok now, now that I found the
real reason for the hard shifts.
Anyway, the reason I replaced the TPS in the first place was because of
hard shift symptom (engine would rev up to 3500 during 1-2 and 2-3rd.
These are hard shifts because the fluid build up more pressure at those
rpms and forces the shift, rather than the PCM making a shift point determination
at a lower rpm (typically 1800 to 2200rpm).
Some users stated that replacing the TPS helped, but in my case
with a defective replacement TPS sensor, it threw me off.
I had to put the original back..fortunately today... the PCM finally provided
a clue with a check engine lite that my code reader indicated was a P-720
(VSS) Vehicle speed sensor (in my 47re transmission) was too low.
I had that replaced today, now the hard shifts are gone.
I've had this problem for a couple months now, and being intermittent,
it made it harder to troubleshoot.
With the VSS replaced today..tranny is shifting just like it used to.
I would suspect that your poor gas mileage is because the engine
is revving at higher rpms consuming more gas before shifting.
I would concentrate on:
1) double checking the voltage o/p on your replacement TPS
to make sure it is working within the range that the PCM
expects.
2) Are you sure that the IAC (idle air control) is working properly?
This is driven by the PCM to adjust the air during idle on when
the engine is experiencing some load like the (A/C on) or wheels turned
and engine is driving the power steering pump more.
3. Also you might consider changing the VSS on the transmission
I never toss the original sensors until I am sure they are defective, because
sometimes even the new ones may not be 100%.
The truck would start ok and idle, and as soon as I put it in Drive and started to roll
and apply the brakes, the rpms on the tach would drop down to 0 and the engine would stall.
Started ok and would idle but again same thing as soon as it started to
move and stop. Turned out to be a bad aftermarket sensor (2.5 v on
closed throttle and 4.75 volt on fully open).
I ended up putting the original TPS sensor back on and measuring it's o/p with a DVM.
Positve lead of DVM to center wire on the TPS 3 wire plug.
(you will need to push the point of the probe into the insulation),
the neg probe to a good engine ground.
*Turn the key on but do not start the engine.*
Measure the TPS voltage with the throttle body closed (you will need to take the air hose off to see this),
then slowly open the throttle by hand all the way up to full opening, and note DVM voltage reading.
The sensor if working should go from around 0.5 v (closed throttle) to 4.5 v full throttle.
(mine read 0.66v (closed) and 3.77 fully open. It was still good.
NOTE: Ignition key on but dont start engine..just operate throttle by hand.
My original TPS is back l on and works ok now, now that I found the
real reason for the hard shifts.
Anyway, the reason I replaced the TPS in the first place was because of
hard shift symptom (engine would rev up to 3500 during 1-2 and 2-3rd.
These are hard shifts because the fluid build up more pressure at those
rpms and forces the shift, rather than the PCM making a shift point determination
at a lower rpm (typically 1800 to 2200rpm).
Some users stated that replacing the TPS helped, but in my case
with a defective replacement TPS sensor, it threw me off.
I had to put the original back..fortunately today... the PCM finally provided
a clue with a check engine lite that my code reader indicated was a P-720
(VSS) Vehicle speed sensor (in my 47re transmission) was too low.
I had that replaced today, now the hard shifts are gone.
I've had this problem for a couple months now, and being intermittent,
it made it harder to troubleshoot.
With the VSS replaced today..tranny is shifting just like it used to.
I would suspect that your poor gas mileage is because the engine
is revving at higher rpms consuming more gas before shifting.
I would concentrate on:
1) double checking the voltage o/p on your replacement TPS
to make sure it is working within the range that the PCM
expects.
2) Are you sure that the IAC (idle air control) is working properly?
This is driven by the PCM to adjust the air during idle on when
the engine is experiencing some load like the (A/C on) or wheels turned
and engine is driving the power steering pump more.
3. Also you might consider changing the VSS on the transmission
I never toss the original sensors until I am sure they are defective, because
sometimes even the new ones may not be 100%.
Waiting for the new VSS that should arrive next week.
#49
03-22-2013 | 03:32 PM
Thread Starter
|
Amateur
Joined: Mar 2009
Posts: 36
Likes: 0
Dang... I can't remember now... I'll check again tonight if it's not raining but I think it must be a typo.. I'm guessing 0.37 close and 3.89 open.
On a side note I accidentitly ordered the wrong VSS from RockAuto and had to send it back.
I did do a bunch of stuff recently and my symptoms suddenly vanished...
My guess is that it has to do with the transmission. Either it's starting to go out or it was running low on fluid. I did all of the above about a month ago and haven't had any symptoms since. I have my fingers crossed but am saving for a new transmission in case (or a new truck). I will be checking all my fluid levels today and if I notice any drops in fluid will most likely start hunting down them leaky hoses.
On a side note I accidentitly ordered the wrong VSS from RockAuto and had to send it back.
I did do a bunch of stuff recently and my symptoms suddenly vanished...
- Replace MAP sensor
- Noticed transmission fluid was low and leaking and added lucus transmission stop leak and filled back up
- Noticed radiator and power steering was low and refilled with stop leaks
- Did an oil change
My guess is that it has to do with the transmission. Either it's starting to go out or it was running low on fluid. I did all of the above about a month ago and haven't had any symptoms since. I have my fingers crossed but am saving for a new transmission in case (or a new truck). I will be checking all my fluid levels today and if I notice any drops in fluid will most likely start hunting down them leaky hoses.
#50
03-22-2013 | 08:30 PM
Amateur
Joined: Feb 2013
Posts: 38
Likes: 0
From: t-town fl
i hate when ihings just fix themselves.......i want to know why lol.......but thats awsome ....as for the tps .ive read it should b high .6x and no more than .8x but look at it like this you have all new sensors sucks but u will have to replace at one point.i also had the same problem and now its gone.have u checked ur pleum plate gasket? thats my next move .i idle at1100rpms in park and 750-900 in drive .2200 rpms at 70 mph seems high to me.