Intermittent Slight hesitation/dragging when cruising along

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norris_309

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Trying to clear up/ get some ideas for my various car issues at the moment!
it's a 2004 b6 avant 1.9tdi 130 (avf)

I've got a feeling I've posted this before, but can't find the thread.
When just cruising along in traffic/ at a constant speed occasionally you can feel the car hold back/drag (hard to describe)
a bit like the feeling you get if you pull the handbrake very slightly (i'm pretty sure it's not the brakes!)

It goes fine if you then put your foot down & it idles fine, just an odd feeling when driving along?
I must add it's a very slight feeling... when you know it doesn't feel 'quite' right.

I'm thinking,
Trying some of that diesel cleaner (never ran that through the car before/any car ever!)
Change diesel filter - looking back, I changed it in feb 2016 on 135k miles, now on 151k (normally change it every other service (so every 2 years/20k miles ish)

Any other ideas on possibilities?
 
I've had the same before... also had so many things changed it's hard to pinpoint exactly what fixed it haha, I'd definately change the oil and filter to start with. Sounds like a classic case of overboost then limp mode which is most likely down to a split intercooler pipe (probably the plastic one at the top) if so this can be replaced or a few people have done more temporary solutions involving clips/tape. Might be worth checking out the EGR which can be cleaned/replaced/deleted. People go one way or the other when it comes to addatives but they can't really do any harm; Forte Advanced Diesel Treatment is my favourite as you just chuck the bottle in with a full tank and forget about it or if you want to put some in each time Miller's oil is alright, I've pretty much tried them all so if your thinking of any others just ask, I also only put premium fuel in (I'm a snob). Best to check nothing is blocking the air filter and the only other real thing I can think of is the cat could be clogged at your mileage which is another thing to clean/replace/delete.
 
Cheers for that, several things to go on!

On looking around on forums, I've found a better work to describe it lol..
It feels 'restricted' and seems more noticeable below 2k revs when keeping a steady speed.

It doesn't go into limp mode as far as I can tell, I've had that in my golf & that really didn't have any power until restarting the engine.
On this one it intermittently feels a bit restricted & pushing the throttle a little it will go fine.

I did wonder about boost leak, guess it could be a very slight leak? not enough to run rough & cause limp mode?
I previously had a split in the small rubber top hose which caused it to run bad, but still no limp mode.

Another thought, I get this noise in the below vid (growl when revs drop), which I've had for years. Sounds like it might be the turbo actuator possibly, maybe that could cause slight issues?
it sometimes sounds almost dump valve like, when you lift off the throttle.


The air filter was replaced in April this year as it failed the MOT on the smoke test.
a retest after changing the filter & ragging it, it still was reading too high?.. related maybe?

As for diesel treatment, was thinking of trying the millers
http://www.halfords.com/motoring/en...l-additives/millers-diesel-power-ecomax-500ml

only as that's the only one I've known anyone use & it did the trick on their car.

Finally, fuel wise, I always use esso as it's local, standard diesel, don't think they do the super
 
Can't say for sure but the noise in that video sounds like some form of leak to me (exhaust near the cat maybe? Although in my experience you also hear a noise that sounds like sucking with that, no idea), probably worth doing a smoke test either way if you have had splits in the intercooler piping in the past. If your exhaust smoke test was reading high and the filter was changed then the most likely case is an intercooler pipe is loose/split, if not it'll be the EGR, cat or dumping too much fuel due to a map, oh another thing worth checking/cleaning/replacing is the MAP sensor. Yeah that's the same stuff I've used in the past, it's alright.
 
I'll grab some of that cleaner.
I've got to do lots of miles in the next week... so maybe a good time to fire in the cleaner, maybe the long motorway run will help it out... this car has various niggles at the moment, that are annoying to say the least.
It's been a brilliant car for years.. damn!

Thanks again for the advice.
 
Last edited:
Just had a thought, (possibly a stupid one?!)
I've read a few times about how you can just remove the rubber hose on the egr valve which then stops the egr working?..
I'm not up on how these things work, but does that mean I could rule out the egr valve being an issue by pulling the pipe out & blocking the end?
 
You can get a blanking plate and do something like this:



Or get a proper delete kit like the Allard one or Darkside (whichever's cheapest really).

If it's an early model A4 you'll get away with no fault code's but the later one's (2003+ maybe?) need a small hole in them to fool the sensor and not give an engine management light (or you can get it mapped out or pull the bulb or just leave it with the light on).
 
Mine is a 2004 so guess I'd get a light on for that then.. damn.
Do you know, if removing the small hose would work though, just as a test to see if the egr is the cause? or is that not advisable?
I really need to look into how these things work so I can understand how removing a pipe or fitting a blanking plate works.
 
Well, fuel filter changed. (new Mann filter)
checked over the plastic pipe along the back which looked fine.

I've also had a little go on the turbo actuator (could just about get my hands in there!), which moves ok, but feels like there is a slight catch as you release it part way out, other than that it moves freely.

Also bought a bottle of the millers ecomax diesel treatment to put in when I fill the car up, although still nervous of that having never used any before & got some motorway miles to do in a few days. I take it nothing bad can come of these treatments?.....

I gave it some 4k rev action once warm on the way to work this morning & it kicked out a bit of smoke.
And seemed to feel ok, but the restricted feeling is intermittent & not always there so to soon to tell if it's helped or not.
 
Right..
I've changed fuel filter.
Added millers ecomax to a full tank of diesel.

Just drove 200 miles and I'm nearly on half a tank!!!
Something is up.
So car feels sluggish, but idles and revs ok? But feels a bit restricted at motorway speed. Kind of driving ok though?

Going by the dash reading I'm over 10-15 mpg down or more.

Amy ideas or things to try.
Once I get it home that is..
My mini cooper s is better on fuel at present!
 
Does it get up to temperature quickly? Might need a thermostat if not, other than that only things I can think of are a clogged EGR, boost leak, exhaust leak or some form of tyre/suspension problem causing low MPG, might sound silly but just getting all four wheels at a fairly high psi makes a world of difference.
 
Yes it gets to temp (90) fine and stays put.
It's quite a recent thermostat.

I've just had 2 tyres put on not tested pressure but they're looking ok.

So looking like egr or boost leak then.
It doesn't feel like when I've had boost leak previously.

Would you know if pulling and plugging egr vacuum pipe would prove if it's the egr at fault? Or would that not help if already clogged?

Got to drive 200 miles home on Wednesday and then another 400 mile round trip on Thursday night! Typical.

I knew it didn't feel quite right recently but didn't realise the fuel consumption was so bad until doing a motorway run.

Thought that might have cleared it.
 
audi upgrades
Plugging it will effectively be the same as removing it so I'd recommend doing that, might get an engine light on if yours is a later model but yeah it should kind of diagnose it I guess, I'd just leave it blocked either way can't do any harm really.
 
Thanks for the advice, can't find anything to plug it with in the holiday home we're staying in..
Will be driving it home tomorrow so will pull the hose when I get back.
I take it the error light that I might get is just an indicator so ok to drive it around?
Can't belive I'm going to have to fill car back up to get home!! Ridiculous

Hope it is something simple! Could do without more bills for cars!
 
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