car hesitates to move when the gas pedal is pressed

[jeyare]

Gents, here is my story.
My problem is based on unexpected “car hesitates to move when the gas pedal is pressed”.
Car – Pajero 3.2DiD 118kW V98W (180k km mileage)

It happened few times (past 2 weeks) during these situations:
– car stopped at lights (to be sure – no Neutral used)
– accelerator pedals pushed, engine RPMs increase to expected range (visually and noisy), no wrong sound
– but car really hesitates to move, speed about max. 5km/h
– several attempts to push the acc. pedal, no change the car speed still like turtle
– it spends 5-10sec and then (magic) car is back into normal operation.
No engine light, no ECU Fault code found.

Till today I found a Fault code: U1120 (by Torque Pro App). I found tons of U1120 dramatic stories, but just this one is logical:
U: OBD-II Diagnostic Network (U) Trouble Code For Engine
1: Fuel And Air Metering
1: Fuel Rail/System Pressure - Too High
2: Turbocharger Boost Sensor A Circuit Low
0: Shift Solenoid E Performance or Stuck Off
Need to measure.

Diagnostic of all measured values (till now) are in normal levels, but just during the normal car operation. Can send if it helps you. Because this situation (car hesitates to move) occurred randomly, no way to measure all the values during whole time of "normal" car operation.

Sometimes (randomly) I feel a delayed reaction of the engine from the acc. pedal. But still no Fault code or the Engine light.

Also checked EGR. No problem found.
But there is still “empty” fault code pool in the ECU.
How is your point?
Thanks.

[jeyare]

update:
- APP sensor checked APP. Both potentiometers provides same values, then no fault discovered. Of course, there is the ECM, that can detects the difference between both values and consequently will provide a APP Fault code. No wires damaged. Nothing.
- TPS sensor checked. Nothing.
- Throtlle plate checked. Nothing.
- EGR valve, this was my first intent to see, if there is some malfunction. Nothing.

[old Jack]

Auto or Manual transmission ?

Are any of the ASC lights illuminating ?

Have you tried driving with ASC selected OFF ?

Have you checked the correct operation and setting of the brake light switch ?

Do you left foot brake ?

OJ.

[jeyare]

Auto or Manual transmission ?

Are any of the ASC lights illuminating ?

Have you tried driving with ASC selected OFF ? Snow mountains.

Have you checked the correct operation and setting of the brake light switch ?

Do you left foot brake ?

OJ.

AT
ASC ilumination - no
driving with ASC off - yes, 3M ago

Re Brakes:
Just to be sure:
- I have open another thread about possible issue in my HBB.
- or did you mean coorect operation and setup of brake lights switch only (no rest of brake environment)? I will check it the switch.

Re: left foot brake - yes, because A/T

Link to my HBB issue:

https://www2.pajeroclub.com.au/forum/showthread.php?t=64435

Thx

[old Jack]

AT
ASC ilumination - no
driving with ASC off - yes, 3M ago

Re Brakes:
Just to be sure:
- I have open another thread about possible issue in my HBB.
- or did you mean coorect operation and setup of brake lights switch only (no rest of brake environment)? I will check it the switch.

Re: left foot brake - yes, because A/T

Link to my HBB issue:

https://www2.pajeroclub.com.au/forum/showthread.php?t=64435

Thx

Try right foot braking and see if it still happens.
I am thinking there is a interlock that limits the amount of accelerator pedal movement that can be applied whilst the brakes are still on, hence my question about the adjustment of the brake light switch and its correct operation, particularly the OFF position, and also my question about left foot braking.


OJ.

[jeyare]

Try right foot braking and see if it still happens.
I am thinking there is a interlock that limits the amount of accelerator pedal movement that can be applied whilst the brakes are still on, hence my question about the adjustment of the brake light switch and its correct operation, particularly the OFF position, and also my question about left foot braking.

OJ.

thx, for an idea. Result:
- there is no interlock mentioned
- no brake light switch issue discovered
- also for the brake pedal in OFF position, no findings.

Measured values from APP sensor in idle (no depressed pedal):
1st Potentiometer: 1016mV
2nd Potentiometer: 488mV (528mV diff)

then max pedal depressed (99,6% of measured range for both):
1st Potentiometer: 4668mV
2nd Potentiometer: 2324mV (2344mV diff) ... seems o be not linear difference

then little bit pedal depressed:
1st Potentiometer: 1406mV (7,0% of measured range)
2nd Potentiometer: 684mV (11,7% of measured range) and (722mV diff)

[Nab]

Sounds more like a transmission or torque convertor issue. If the engine still revs up and sounds normal the car should still move normally.



I think there may be an issue with your throttle but that doesn't sound like it is causing no drive.

[jeyare]

Sounds more like a transmission or torque convertor issue. If the engine still revs up and sounds normal the car should still move normally.

I think there may be an issue with your throttle but that doesn't sound like it is causing no drive.

Thx for your point.
Torque converter seems to be a reason, but not for "randomly" discovered issue of hesitated car. Another point - for such source from the torque converter you have to listen clicking or a revving noise (as converter source indication). Nothing like this.

Second: bad torque converter will take the transmission longer to engage the engine, resulting in higher than normal stall speeds. I have different symptoms - I have revs but with sustained 5km/h speed (not stalled) till the miracle, when car is switching into normal (no foreign sounds there during the switch to normal).

Third: most common symptom for the converter is a shuddering. Nothing happened.

The Throttle - checked. Still 100% open.

[4ePikanini]

Atf level should be your first check
If thats all good, double check tranny wiring and connectors

Your issue is likely atf level or valve chest (mechanical or electrical or wiring)

Sent from my S60 Lite using Tapatalk

[old Jack]

All the reported intermittent symptoms still point towards the brake switch is not releasing correctly so the AT ECU still thinks the brakes are applied.

The INVECS Adaptive Learning AT program has several built in self protection functions that limit engine power if the brakes are still applied (or the AT ECU is getting a signal that the brakes are still applied) and or the wheel speed is low compared to engine rpm. This is to protect the torque convertor from damage. Brake switch is a cheap and easy replacement so this would be my first action if I could not fault the switch or its adjustment.

Or there is some intermittent problem with the signal from the accelerator pedal but the OP has checked these and at the time of checking they were OK. The only way to exclude these are to either replace the sensors or wire in two digital voltmeters and monitor the voltage during normal and abnormal conditions.

OJ.

[craka]

Due to this" Turbocharger Boost Sensor A Circuit Low. " and if your pajero is a NS model. I'd be checking all your vacuum hoses around the turbo circuit. Especially the one near the MAP port of engine. Really need a vacuum pump or similar as you may not be able to visually see a problem with hose.

Car will still rev if you have leaking vacuum hose but car will not perform as normal. If the turbo is not in boost pressure due to leaky vacuum hoses, I would think that your fuel air errors would be as a result of the above.

There are a number of us NS owners that have had a perished vacuum hose near the MAP port, that has given us grief, and similar issue.

[Nab]

An odd one for sure. In my mind, if the engine still revs(even if not 100% properly, missing, backfiring etc) when in drive it should still move from a standstill regardless. How high does the engine rev when it’s not moving? Do you mean idling, 1500rpm, 2500rpm?? Anything above idle will get you above 5kph unless as OJ said it thinks the brakes are on and is limiting power.

[craka]

Sorry , just noticed the part where the OP stated only 5km/h . What I was describing wouldn't cause that. I think OJ is on point.

[jeyare]

All the reported intermittent symptoms still point towards the brake switch is not releasing correctly so the AT ECU still thinks the brakes are applied.

The INVECS Adaptive Learning AT program has several built in self protection functions that limit engine power if the brakes are still applied (or the AT ECU is getting a signal that the brakes are still applied) and or the wheel speed is low compared to engine rpm. This is to protect the torque convertor from damage. Brake switch is a cheap and easy replacement so this would be my first action if I could not fault the switch or its adjustment.

Or there is some intermittent problem with the signal from the accelerator pedal but the OP has checked these and at the time of checking they were OK. The only way to exclude these are to either replace the sensors or wire in two digital voltmeters and monitor the voltage during normal and abnormal conditions.

OJ.

Thanks OJ and all the rest gents, I appreciate your attitude.
For me the INVECS self destruction protection in A/T is reasonable. I will check it the brake switch again.
I found it also in official Mitsu check list for the A/T troubles - check a Stop lamp switch - Brake pedal: Depressed (ON) & Brake pedal: Released (OFF). There are 4 pins and the 1-2 is for Stop lamp. Needs measure by ohmmeter of continuity (when is released) or no continuity (when is pusshed). Pushed range must be 4 +/-0.5mm.

Same findings for the APP sensor - why is not there a Fault code:
If accelerator pedal position sensor output voltage is 0.2 V or lower at times other than when the engine is idling, the output is judged to be too low and code No.21 is set. ..... Main is in expected value range 500-4000mV. Then APP is out of suspicious. But still open logging in my Android Torque APP connected to ECU (logged all info from ECU, also for both potentiometers), no suspicious data there (but still not yet happened the car hesitate issue from permanent logging). Really recommended feature, because you can read by MS Excel all the data.

Thanks again!

[Peterng]

Humour me..

Have you tried in "Manual" mode on starting from stand still?