Lumpy running
QRecently, the idle on my Volkswagen Touran 1.4 TSI with the CAVB engine has been lumpy. With the air-conditioning running, the engine revs fluctuate from 740-790rpm – at the lower revs, it feels as though it is about to stall. With the air-con off, the fluctuation in revs is lower by around 10rpm. I am able to read this as I have a Kufatec Fiscon Bluetooth installed on my vehicle.
I also find that the turbocharger occasionally runs below 1500rpm, whereas previously it was closer to 2000rpm. Consequently, the engine is not running smoothly. I have checked using VCDS and not impossible – that both crash sensors have failed simultaneously. Given this, the most likely fault will be with the airbag control module (J234). I would clean the connections to J234 first, then inspect the other connections as you have suggested. Failure to rectify the problem may indicate that the J234 unit has failed.
Advice regarding the disconnection of the battery from both Autodata and VAG is that the ignition should be OFF when the earth lead is disconnected and ON when reconnected. The ignition being there are no fault codes.
Mileage is more than 116,000 kilometres, with the spark plugs due for replacement at 120,000. What should I be checking to determine the lumpy idling and running? Alex Goei
AGiven the symptoms and the change in turbocharger running speed, my first checks would be to the vacuum pipes on the engine, particularly those connected to the charge pressure control solenoid valve (N75). This would be the most likely cause of your problems.
Another area to check is the EVAP system. When checking this, I would focus on the active charcoal filter system solenoid valve (N80). This is located close to the throttle valve module. As you are also close to the mileage for a spark plug replacement, I would change these now. This will at least eliminate them from being a possible cause. on during reconnection does apparently lessen the surge of voltage.
The T28 terminal is a 28-pin multi-plug and can be found behind the trim by following the loom upwards towards the A-post.
I would concur with your plan of action for faults two and three, particularly inspecting the hoses/pipework.
The wiper switch fault may also be due to a poor connection and I would check the connections to the switch and in the loom first.