Strange Problem

[Fergy]

Ok this will probably sound a bit strange. Firstly my car is a 2008 Leon Fr tdi with 58K on the clock. Its been serviced regularly since new and there are no lights up on the dash at any time.

This problem has happened several times and is intermittant but it has me stumped. When out driving the exhaust note would change and become throatier almost like a baffle or something has came lose. The exhaust is the standard exhaust and the noise only appears ocassionaly.
When this noise does appear the car lacks power as if the turbo is not working. It will pull hard for a few seconds then drop off.
It will rev (so its def not a dpf or limp mode) but there is no pull or urgency. The noise does eventually cut out and the power does come back but this could take a few minutes or the next time the car is started/reset. Any other time the car pulls well and the turbo is working fine.

I know its a bit of a strange one so im wondering if anyone has any suggestions or similar problems.

Im going to strip the EGR valve and intake at the weekend for a good look and hopefully get the turbo cleaned out with some innotec turbo cleaner just to eliminate these two issues. Though i dont think its a problem with either as the car doesnt go into limp mode or any lights come up on the dash.

Cheers guys

 

[LeonCR]

Sounds like its doing a DPF regen

Wouldnt worry about it if its not causing any issues

 

[Fergy]

But the car is doing it at an ever increasing rate now. The last time the dpf light came on and it needed a regen and it cleared the dash lights.

Dont the revs increase automatically when its trying to do a dpf regen?

 

[LeonCR]

what sort of trips do you do in you car ?

and how many miles between this issue reoccurring

 

[TllEWL]

I don't see how revs can increase if it's connected by gears to the wheels which are in constant contact with the road ....unless you drive faster of course

 

[LeonCR]

Revs would increase at idle when a regen is taking place

 

[TllEWL]

Touché

 

[Fergy]

Im doing trips of around 30miles motorway/country roads very little urban driving. This could happen a few times on each journey. Mostly the noise from the exhaust indicates this problem is going to happen because the exhaust note becomes deeper and throatier, more like a straight through system

 

[LeonCR]

Do you give it a good thrashing every now and then ?


Does sound like its doing a regen to me

 

[Fergy]

Oh yes it gets a good thrashing (all on private roads) just to clean out the cobwebs. When this problem happens and shes at idle theres no increased revs. My knowledge of a dpf regen is that the revs will increase above the normal idle to cause an overfuel and burn off the soot in the dpf.

 

[LeonCR]

depending on the type of regen thats happening

active or passive

Active will increase the revs @ idle while passive will just do it as your driving

how many miles between the times this happens ?

 

[Fergy]

Its intermittant one day it could just happen the once, the next it could happen a few times on the same 30 mile journey. Also the length of time this condition lasts varies from 5/10mins to almost my complete journey into work.

 

[LeonCR]

have you tried a 20 min drive in 4th @ 60+ MPH to give to a chance to fully regen if that's what its trying to do

 

[Fergy]

Ill give that a try but most of my driving is on motorway or country roads at 60+mph.

I still cant understand why this noise is coming from the exhaust and why its so intermittant.

 

[LeonCR]

Ill give that a try but most of my driving is on motorway or country roads at 60+mph.

I still cant understand why this noise is coming from the exhaust and why its so intermittant.

Th exhaust note will change as extra fuel is being dumped into it to heat the DPF to 600+ degrees its noral for when a regen happens

 

[Fergy]

But this is sounding like a blowout and has been happening since i first got the car 3yrs ago. Its only the sluggishness and slow response has been happening recently.

The last time the dpf light was on and i had to force a regen on the motorway by holding the revs @2000rpm and 60mph there was no change in the exhaust note.

I shall try whjat you said on the way home tonight and see if it has any affect.

 

[LeonCR]

But this is sounding like a blowout and has been happening since i first got the car 3yrs ago. Its only the sluggishness and slow response has been happening recently.

The last time the dpf light was on and i had to force a regen on the motorway by holding the revs @2000rpm and 60mph there was no change in the exhaust note.

I shall try whjat you said on the way home tonight and see if it has any affect.

How many miles has your car done ?

 

[Fergy]

58k coming up on its major service. The service and cam belt are going to cost £500.

Im trying to work out if this going to be a quick fix or something more serious so i can decide whether its worth putting the car through the servicing or just trade it in and cut my losses. As ive had a brave few problems with sensors etc in the past.

 

[steroidchris]

Mine has the regen symptoms at normal revs too. There are quite a few people on here that have had exactly the same and there is no fix to date.

The only proper fix is to get the dpf delete, which I'm saving the pennies for because this issue and the proper regen process pisses the **** out of me.

 

[Danny_FR]

Mine does exactly the same thing but performance isn't affected as such. What I get instead is more like a jerking effect between about 1700 and 2200rpm. It's almost like it's misfiring. I get the same increased exhaust noise, which with my removed rear silencer, sounds pretty good! There is no pattern to it happening and my car gets plenty of "thrashing" with no short journeys. I have never had the PDF light on. I was pretty certain it was DPF related but this thread has just confirmed my suspicions even more.