Mysterious rattles, poor fuel consumption, difficulties in starting, low power, weak acceleration. It has emerged that many drivers who have been through the dealer “upgrade” following the Volkswagen scandal are complaining that their once-trusty vehicles are a shadow of their former selves.

So far almost 500,000 of the 1.2m affected VW, Audi, Seat and Skoda diesel cars have been returned as part of the official dealer recall. Most require a simple software upgrade, but some – those with the 1.6 litre diesel engine – have required major work.

With growing numbers of returnees complaining their cars have since suffered serious problems, others are questioning whether they want to take the risk and have the work done too.

Volkswagen says the number of affected drivers is tiny, although with reports of problems on some websites growing fast, the drivers argue that it can’t just be a coincidence.

Some owners yet to do the recall are questioning if they can avoid having to do it, and whether it is a legal requirement. But this week the Department for Transport confirmed that the emissions recall is entirely voluntary, and there are no personal ramifications for not having the work done. Environmentalists, though, are likely to disagree.

The four brands within the Volkswagen group (VAG) are collectively recalling 20,000 cars a week, but drivers may first want to examine a long thread on the HonestJohn motoring website in which owners have chronicled their experience. In a vast stream of comments, VW, Audi, Skoda and Seat owners complain about problems following the upgrade. There is a similar thread on Facebook. Many owners say their cars were working perfectly before the recall; others that their vehicles broke down soon after their visit to the dealer. Some drivers have significant repairs bills and are furious at their treatment. Many say this will be their last VAG vehicle. One poster on the HonestJohn thread, who claims to be an ex-VW service manager, advises owners to take their cars to a specialist to reverse the software update with a re-map.

This week Guardian Money was contacted by reader James Harrison who says the recall has ruined his car. His family’s 2010 Golf 1.6 diesel required a significant change to the engine. However, Harrison claims the car, which has done 50,000 miles, has become almost undriveable since the work was done. “The car has begun to stall intermittently, and is difficult to restart. It used to go into ‘regeneration mode’ [whereby soot collected in a filter is burnt off at high temperature to leave only a tiny ash residue] a few times a year, but now does it on almost every journey. This is my wife’s car and is used to transport our two children. As far as I can see they have ruined a perfectly working car.”

The four brands in the VW group are collectively recalling 20,000 cars a week. Photograph: Armin Weigel/EPA

The Sheffield-based electronics engineer says he was given to understand that the work was mandatory, but has since learned this is not the case. Some dealers have even been automatically doing the work on any car brought in to be serviced – sometimes against the owner’s explicit instructions. “I am concerned at the long-term impact this will have. If the car is regenerating every day, what will this do to the lifespan of the EGR [exhaust gas recirculation] valve and the rest of the exhaust system, which cost thousands to fix if they go wrong?” Harrison says. “I am in the process of fighting with the dealership that completed the modification to get it to accept that there is a fault with the car – but all I’m getting is denials. We have a Skoda that is also affected by the recall. At the moment I won’t be taking it anywhere near the dealer when the recall letter arrives,” he says.

HonestJohn has became a focal point for affected owners. The website says VW engineers have assured it, at a specially arranged meeting, that problems persist only for a tiny number of owners that had the work done. “VAG says that out of 480,000 fixes applied, there have only been 3,600 complaints. It says that only 150 cases of problems after the fix remain outstanding. All we can now do is monitor the situation,”says the man behind HonestJohn. Asked whether he would recommend that others accept the recall, he said: “I wouldn’t have it done unless I had to”.

All this will only heap more pressure on VAG to end what critics say is a culture of denial, and to start compensating affected owners. This week it emerged that more than 35,000 motorists have joined a class action lawsuit against VW in England and Wales over the emissions scandal. The size of the group is increasing at a rate of 500 drivers a day, and lawyers are confident the action will eventually involve 100,000. Lawyers claim British drivers should be compensated because they paid more for what they thought were clean diesel cars. Each motorist is seeking thousands of pounds in compensation.

Earlier this month VW pleaded guilty to criminal charges in the US, admitting to a scheme to sidestep pollution rules on around 600,000 vehicles. It admitted conspiracy and obstruction of justice in a scheme which used software called a “defeat device” to suppress emissions of nitrogen oxide during tests. The firm has agreed to pay $4.3bn (£3.5bn) in civil and criminal penalties in the US, but in the UK the government has not taken the carmaker to court over the scandal.

A spokesman for VW denied there is a problem, restating that the number of complaints is less than 0.02% of the 540,000 completed cases. “We have engaged constructively with our customers. They are our top priority, and the vast majority are satisfied.” He said the firm would not compensate owners on the basis that the issue hasn’t caused “any loss of engine performance, fuel economy or an increase in running costs”. In response to Harrison’s claims he said: “We’ve advised the customer to arrange to have his concerns investigated, which is taking place at his local dealer. We will continue to offer support.”

Driven to distraction

Photograph: Simon Stuart-Miller (commissioned)

• Had the emissions update on my Audi A4 2.0 TDi and wish I hadn’t! The judder from the engine when cold was appalling. The dealer’s had it for three weeks and done numerous tests, but Audi said there’s no way the update could have caused this, as it only removes a piece of software! Apparently it’s pure coincidence my car drives like an old tank when the engine is cold!

• Had the software update, our Passat spluttered and died on us.

• After the update my 2012 Passat Estate 2.0 TDI is a sluggish, underpowered donkey.

• My 2 litre 140BHP Seat Exeo had the update a couple of weeks ago. I’ve not noticed any difference in the way it drives but the MPG is down 5%-10%.

• The DPF [diesel particulate filter] is regenerating three or four times a week and filling the car with fumes. Also lots of smoke coming from the exhaust … didn’t happen before the upgrade.

• Our 2012 Tiguan 2.0 TDi BlueMotion was returned with obvious loss of power at 1,000-2,000 RPM. First (VW) mechanic that tested it confirmed the motor lacked power.

• After the update our car was returned with the engine light on. At first they couldn’t figure out why, then said an air intake actuator would need to be replaced and would cost me £600.

• This is the reason I left Volkswagen. My conscience would not let me carry on telling loyal customers that the new version of engine management software was not causing the problems you all seem to be suffering. If any of the customers who I had contact with are reading this forum I can only apologise. You don’t legally have to get the recall done, it is not safety related. It causes more harm than it cures.

Source: HonestJohn.co.uk. All postings since September 2016