Hesitation under throttle
Q I have a friend with a 2007 Ford S-MAX 2.5 T petrol manual with the engine code HUWA. The car has covered around 90,000 miles. It was a one-owner car with a good service history, but since the very start of his ownership it has had a hesitation when climbing up through the revs. When the engine is very warm – say, in the summer months or if you let it get very warm by letting it sit and idle – then it reacts very violently when setting off and climbing through the revs – it’s almost kangaroo-like, but you have to be accelerating quite quickly.
I downloaded the fault codes and there was one at the top of the pile which looked suspicious: ‘P061A – Internal control module torque performance – event information – pending’. The two other codes listed were ‘C2003 – Steering wheel switch left module – internal fault – Intermittent’ and ‘B10AC – Cruise control switch – Faulty mounted – Intermittent’. I cleared the codes using my Delphi DS150E diagnostic system.
We also picked out a couple of live data feeds to monitor – one was absolute load and the other was the throttle position; both were graphed against engine speed as he drove. The load graph seemed to be smooth and progressive, while the throttle position seemed to follow the revs up to a peak but then sometimes the graph didn’t seem that smooth. I didn’t get to see the graph when the violent kangarooing started. When we got back home, the ‘P061A’ code was back, but the other two didn’t reoccur.
He has taken the car to a couple of garages but they haven’t been able to fix the fault. Here is a list of what has been changed: the camshaft drivebelt (it was overdue on time and mileage, I believe), spark plugs, coils (all five), both Lambda sensors, inlet and outlet camshaft solenoid valves, turbo boost control solenoid and crank sensor.
My feeling is that the issue could be related to the throttle, as it feels as though you are jumping on and off the throttle at its worst and, at best, it’s a hesitation as you climb up through the revs. Also, when mapping the live data, the throttle graph didn’t seem 100% right somehow, but there was nothing conclusive in the short time I spent on it.
What are your thoughts on the fault and code present in the car? Is there anything else I need to monitor in the live data? David Saville A The code ‘P061A’ is very relevant and is the most likely source of the problems. The code is triggered when the torque signal calculation from the mass airflow sensor does not equate to that given by the throttle pedal sensor. This may indicate that there are internal problems with the ECU, but before sending this off for testing I would first clean the airflow sensor to see if this improves matters.
The airflow sensor can be cleaned with either a proprietary spray or isopropyl alcohol. The hotwire should not be touched during the cleaning process and you should ensure that it is perfectly dry before starting the engine afterwards.
It would also be worth checking the integrity and continuity of the wiring between the ECU and sensors, to ensure that there is not a fault in the loom which is activated when the engine moves slightly under the torque of driving.
As you have already checked that the throttle pedal position corresponds to the actual position using the live data, if cleaning the airflow sensor has no effect, then try sending the ECU for testing at either ecutesting.com or bba-reman.com