Some time ago I read a letter from someone that said supermarket diesel lacked something and this could cause issues? Is this true?
It's just that 3 months ago my engine management light came on after a long motorway run, it went into what I believe is called "limp mode" just as I came off the motorway, which is very apt as it struggled up-hills etc all of the way home (28 miles). Next day it seemed fine & the light was off BUT as I was worried it went into the agents and they "replaced pipe from BO EPPC to valve as it had split and cleaned and refitted the plug to boost the EPPC as it was corroded" (

?).
But, yesterday, once again, I did a long run (225 miles each way) and on the way back (just before getting onto the motorway) it happened again (it sort of "coughs" not exactly a misfire then just no real response to the accelerator). Although I suspected that stopping & starting the engine may clear the problem there was also the danger it also may just not restart (200 miles from home with my dog in the boot!). So, I drove past several services with the car struggling at 40 uphill (no fun through the Lakes!), and at 60 on the flat despite my foot being fairly hard-down, occasionally getting to 70-80 downhill – it would respond to the accelerator for a while but then lose power again.
So, I pulled into some services just 60 miles from home (guessed that if I had to call my breakdown service and they wouldn’t let the dog into the cab 60 miles wasn’t too far for him!). I turned off the engine, took the boy for a leg stretch, started the engine again (10 minute break) – started fine, is fine now – have been on a 150-mile round trip today (I do do lots of miles).
So, question, any ideas? Is my driving to blame? Could it be the EGR valve? Do I need to get it into the garage straight away or I’ll ruin the engine? HELP! I'd hoped that I'd get 200K out of her but she's only got 93K on the clock!
Thanks in advance (and sorry for the War&Peace size post).