I drive a 63 plate 1.6 tdci fiesta, and it has a TDI tuning box that was installed by a previous owner, had absolutely no problems with it until yesterday. Last night the power train warning lamp came on after a very short drive to the shops, and the car went into limp mode.

Engine off and on again and the car was no longer in limp mode but after a few seconds the car juddered and went back into limp mode and flashed up the same warning. This morning I tried to take the car to a garage but it eventually cut out so I had to have it recovered and dragged there.

I don't know what codes flashed up specifically but one was for low fuel pressure and another was for egr valve frozen. So the garage replaced the fuel filter, something I had been planning on doing but hadn't gotten around to, this seems to have somewhat improved the situation but not fully.

Now the car drives as normal, with no real difference, after 2k revs I can begin to hear the turbo spooling up, it seems to be a fair bit louder than before and has some slight rattle to it, but it doesn't sound massively concerning.

 Around 3k revs the car will flash up the Power train warning lamp and then drop into limp mode again. This all only happens when in gear and being driven, if the car is idle and not in gear the car can be revved to 6k with no issues.

The garage is unsure what is happening and think there's a possibility it's to do with the TDI tuning box, so I'll be removing that tomorrow, I'll also try to remove and clean the egr valve in hopes of freeing that up, has anyone got any idea what could be the cause of the issues or any advice where I should begin looking?

Thanks in advance

Is it a replicable tuning box supplier contact them first before removing unless its a simple plug and play. I had a similar problem with limp mode in my vauxhall zafira (no curb appeal😁) it was a fuel rail sensor.

22 hours ago, st line x 140 driver said:

Is it a replicable tuning box supplier contact them first before removing unless its a simple plug and play. I had a similar problem with limp mode in my vauxhall zafira (no curb appeal😁) it was a fuel rail sensor.

Had it plugged in again the next day as it wouldn't start, fuel pressure was low so I had thet TDI tuning box off and that seems to have remedied the problem, still not sure I trust the car so I'll be driving it as carefully as I can for a bit, will definitely be running some carbon cleaner through her soon and giving that egr valve a clean 

what make is the tuning box? good at least car works without.

I'm not a fan of them personally voids warranty on new cars unless from replicable supplier increase in insurance and like most remaps start stop doesn't work anymore. So say you get better fuel economy but performance is increased just like fuel consumption. Also increases wear on engine. and car might not pass emissions test at MOT time.

It's made by a company called TDI, had no problems with the car since it's come off, tempted to see if I can have it sent back to he tested/reconditioned to sell it on.

Luckily it passed the mot emissions test fine and my mpg doesn't seem to be much different either way to be honest, have noticed a big difference in the torque of the car, feels almost gutless without it