Mysterious and sudden power loss

Old Bloke

Active Member
Jan 30, 2014
45
0
Oxfordshire
This is one of those weird occasions where my 2003 Seat Toledo 1.9 TDI has on a couple of occasions suddenly had a loss of power momentarily under acceleration then carried on as normal, it felt like no fuel was getting through. No warning lights or engine management lights have come on during this glitch or afterwards. She has always been serviced on time by a dealership until I decided to do it myself as she is now 13 years old but in good fettle. As a precaution I changed the fuel filter this time, and yes I did fill it to the brim with diesel before reattaching the pipework, I then ran her up and checked the fuel flow through the clear plastic pipe from the filter to the pump which I could see the occasional bubble in the fuel flow when I raised the revs from idle and wondered if a pipe has developed a split underneath allowing air to get sucked in.
Other than this she runs perfectly and once at constant speed gives no worries.
Any ideas out there in Seatland that I may have overlooked
Thanks for any replies.
 

chriswales6

Active Member
Mar 2, 2016
294
47
I've owned a 2003 TDI 110 Leon for ten years and have been servicing it myself for the last couple of years.

The clear fuel line is normally the return from the fuel pump and air bubbles are normal. Depending on which model of TDI you have the turbo could be starting to act up. Sounds like you're getting a flat spot in the acceleration where the power seems to drop off for a few hundred revs then picks up again. My car occasionally does this which I take as a warning sign that soon I'm likely to get the over boost / limp mode problem. Where you lose most of the power until the engine is restarted.

The TDI 90 has a very simple fixed turbo that doesn't give many problems. If you have one of these then the problem maybe with the fuel pump or an injector. If you access to VCDS on a laptop or fault code reader then you could check for any problems logged.

The TDI 110 and above have variable geometry turbos that improve the response and power. If they're only used on short runs for example under 10 miles the turbo doesn't hot enough to clear the soot off the moving vanes. After a while they become unresponsive, first sticking a little to give flat spots in the acceleration then sticking more and over speeding the turbo. At which point the ECU triggers limp mode to protect the turbo.

If you do a google search there are a number of ways to cure a sticky turbo. A garage would most likely want to replace the turbo, it's the simplest solution for them and stops you coming back in a few months with the same problem. The DIY way would be to first check the rubber vacuum line to VNT vane actuator, it could be split. Then check if actuator rod to see if moves freely, if not then the turbo needs to be cleaned. This can either be done by taking the turbo apart or spraying a cleaning into it while it's still on the car.

Personally I choose the Italian tune-up method on a local dual carriageway. Drove ten miles up the road warming the car up and checking for speed cameras. Then turned around and caned it back the other way, taking the car pasted 4k revs in each gear and holding it flat out in 4th or 5th for as long as I could. Doing this around once a month stopped the problem.
 

Old Bloke

Active Member
Jan 30, 2014
45
0
Oxfordshire
Thanks for the input Chris, it makes sense as our Toledo was used on trips of 20 plus miles all the time until recently . I have added the cleaning additives to fill ups which have improved the performance and turbo response with no power fade. I will of course take her on the Motorway once a week for the Italian warm up know as the Pudda da foot down to clear the vanes.
 

johanbaguca

Active Member
Jul 23, 2017
27
1
Im having the same problem with the sudden power cut, first time it happened during an overtake and it went directly in to limp mode, i restarted the engine and it was fine after that, im going for a long mountain road drive today followed by a long highway stretch during which ill apply the italian tune ip mode, hopefully not damaging anything


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