Revs hang after hard acceleration

[Tony500]

Does anyone else get this symptom after acceleration hard on a d5 185? Our car used to suffer a lot from this, until I replaced the swirl flaps but after a few months it happens again? Found myself in a tight spot after the plonker infront slams the brakes on and indicates right at the last min, I had to pull into the left lane and accelerate hard and the revs don’t go lower than 1500rpm if I stop or drive slow. I can pull to the side of the road and it will slowly return to normal but when I tap/press the gas it will return to high revs/idle. To solve the problem I have to turn the car off for around 2 mins with the car locked for it to reset. No faults on Vida either.... any clues?

[Tannaton]

Originally Posted by Tony500

Does anyone else get this symptom after acceleration hard on a d5 185? Our car used to suffer a lot from this, until I replaced the swirl flaps but after a few months it happens again? Found myself in a tight spot after the plonker infront slams the brakes on and indicates right at the last min, I had to pull into the left lane and accelerate hard and the revs don’t go lower than 1500rpm if I stop or drive slow. I can pull to the side of the road and it will slowly return to normal but when I tap/press the gas it will return to high revs/idle. To solve the problem I have to turn the car off for around 2 mins with the car locked for it to reset. No faults on Vida either.... any clues?

The auto gearbox has a sport mode which you activate by PLANTING the throttle to the floor - this gives you the usual sport mode i.e. more aggressive shifting and higher RPM shift points.

However.... I would expect the gearbox to revert to normal driving mode after say 5-7 seconds of no acceleration, it sounds like you are waiting much longer than this?

Tip: Try moving the gear lever over into geartronic, shifting up a gear and then drop back into auto mode. I'm not suggesting this is a fix, it would be interesting to see what it does?

[gmonag]

I hate guessing, but you say that there are no DTCs. I would suspect the throttle position sensor. See if you can graph the output.

[barrybritcher]

sounds like oil in the vacuum pipes and the engine is consuming it as if it was diesel

[Tony500]

Originally Posted by Tannaton

The auto gearbox has a sport mode which you activate by PLANTING the throttle to the floor - this gives you the usual sport mode i.e. more aggressive shifting and higher RPM shift points.

However.... I would expect the gearbox to revert to normal driving mode after say 5-7 seconds of no acceleration, it sounds like you are waiting much longer than this?

Tip: Try moving the gear lever over into geartronic, shifting up a gear and then drop back into auto mode. I'm not suggesting this is a fix, it would be interesting to see what it does?

Hi thanks for the reply, I’ve tried that a few months ago before I done the swirl flaps. Still revs at 1500rpm and tries to pull forward when foot is on the brake.

[Tony500]

Originally Posted by gmonag

I hate guessing, but you say that there are no DTCs. I would suspect the throttle position sensor. See if you can graph the output.

Thanks for the reply, I will hook Vida back up once I get time off work ect... Tbh I should have checked this by now but I’ve not thought of that yet lol. On the to do list.

[Tony500]

Originally Posted by barrybritcher

sounds like oil in the vacuum pipes and the engine is consuming it as if it was diesel

Thanks for the reply. I’ve recently changed engine mounts and no oil in them, the tcv ect are all oil free too unless there is something else I’ve missed?

[Tannaton]

Originally Posted by gmonag

I hate guessing, but you say that there are no DTCs. I would suspect the throttle position sensor. See if you can graph the output.

Good point - though I would suspect that if it is the TPS it's more likely to be a mechanical issues with it as it has dual, redundant circuits.

[Tony500]

Originally Posted by Tannaton

Good point - though I would suspect that if it is the TPS it's more likely to be a mechanical issues with it as it has dual, redundant circuits.

Should have time to have a look over the car tomorrow. Where abouts is the tps located on the 07 d5 185 xc90?

Thanks

[gmonag]

It is more correctly called the Accelerator Pedal Position Sensor and it's located at the accelerator pedal.

From VIDA:

The function of the accelerator pedal (AP) position sensor is to provide the engine control module (ECM) with information about the position of the accelerator pedal. This information is used by the control module to control engine torque.

The sensor consists of a plastic housing with two potentiometers, an AC/DC converter and circuits. The potentiometers are connected to a shaft which is affected by the position of the accelerator pedal (AP). The resistance in the potentiometers changes with the position of the accelerator pedal (AP).
The accelerator pedal (AP) position sensor transmits an analog and a digital signal (pulse width modulated (PWM) signal) to the control module. These signals indicate the position of the accelerator pedal (AP). The digital signal is generated by the sensors AC/DC converter.
The analog and digital signals are used at the same time by the control module to regulate the fuel volume.
The sensor is supplied with 12 V by the system relay via a fuse and is grounded to the body.

The digital signal is used in conjunction with the analog signal for accelerator pedal (AP) position sensor diagnostics. The accelerator pedal (AP) position sensor signals can be read using VIDA. A diagnostic trouble code (DTC) is stored if the engine control module (ECM) detects a difference between the analog and digital signals. The engine control module (ECM) then uses a minimal value to ensure the function (limp home).

The accelerator pedal (AP) position sensor is located on the accelerator pedal bracket.

Good luck.