Hi all, 

I have recently purchased an old A4 b6 avant 2.5 tdi quattro 180bhp, 

I have one of those ODB2 adapters and the android app TORQUE, which reads out power put down etc, 

I plugged it in and went for a... steady drive... and the max I could get it to read out was 130BHP, 

I know I should probably take the read out with a pinch of salt but even still 50bhp off what it should be is quite alot...

So, now I need to make a plan on how to recoupe said horses and I need your help of things to do/replace in order to get them! 

I have scanned for errors and there is none, also, the car has done 190k!! (full service history) 


So here is my proposed list to do/buy, please let me know if I have missed anything (which I'm sure I have):

1, EGR valve delete
2, Injectors (prob wont buy any replacements due to price!!)
3, Full service inc k&n panel
4, Gearbox oil
5, rear diff oil
6, engine/gearbox mounts? (Not sure about this but seen a thread about replacing something called the snub mount or something??)


Anything else I have missed? Glow plugs are just for engine start I think so they wouldn't need replacing for bhp, 

Is the turbo something that may be waring out, or is that something thats either working or its not, no in-between?

Any comments would be greatly appreciated, 

bump?

I'm not sure how reliable that app is for providing accurate power etc? I would expect a car to lose a little power after that sort of mileage but not 50bhp. I would be inclined to get a full service done and maybe take it to a specialist with a rolling road after this just to see if you get similar results. Are you happy with the way it drives? Does it feel like it's down on power?

It doesn't feel like 180 thats for sure, lol, 

 

As you say I may take it rolling road just to put my mind at ease (or confirm suspicions )

May well be worthwhile just to find out for sure. I would be interested to see how accurate the Torque app was in comparison!

Will let you know, I've just blanked off the EGR valve, not changed much, 

Blanking off the EGR on an old diesel is a good start, but it could be closing the stable door after the horse has bolted.

 

That's because the EGR doesn't just recirculate exhaust gas, it recirculates soot and unburned diesel as well.  These two mix together and coat the inside of the entire induction system with a thick, sticky goo.  This builds up and can entirely block the inside of the inlet manifold and inlet ports as well as the EGR valve itself.

 

My last car was a diesel and it had a 5mm layer of this gunk all over the inside of the manifold.  Cleaning this and the EGR valve gained me 15 bhp and a much smoother, more responsive engine.  A thicker layer would have robbed me of more power.  I've seen photos of EGR's that were almost entirely full of this stuff, so the manifold would be the same.

 

I strongly suggest you get the inlet manifold off and clean inside it and the inlet ports as well.  Just make sure no muck gets down into the engine.  You will probably need new manifold gaskets to ensure a good seal.  Use Carb cleaner and wear rubber gloves, no kidding.

 

Check the air filter element is not clogged.

 

Check all the hoses between the turbo and the inlet manifold in case any are leaking and losing your turbo boost pressure.

 

Check that the outside of the intercooler is not blocked by dirt and debris.  If it is not cooling the inlet air, it will be robbing you of power.

 

Get some fuel system cleaner like PowerEnhancer.  This cleans the injectors, fuel pump, and combustion chambers and costs about £20 when on offer.  Make sure you follow the instructions fully.  Birmingham Audi are doing an offer at the moment for something similar for £15.

 

Or you could try TerraClean (instead of PowerEnhancer), which is like a power washer that cleans inside the engine's combustion chambers.  Expensive at about £70 or more a go.

 

Start using a good fuel like Shell VPower that continues cleaning the fuel system after the PowerEnhancer has done its job.  Use it exclusively for the first month then one fill-up in every four or five to keep the muck from building up.

 

Take off the catalytic converter, turn it upside down and thump it fairy gently to loosen and remove the built-up soot inside it, then put it back on.  This reduces the resistance to the exhaust gas flow.

 

There might be blow-by around the piston rings, losing pressure and therefore losing power.

 

There might be a leak from the cylinder head gasket, also losing pressure and therefore losing power.

 

Have the fuel pump checked to see if it is giving enough pressure to get the right amount of fuel through the injectors.

 

Have the injectors checked to ensure they are working properly.

 

Oops posted by accident

Much love! thanks for the comprehensive reply I appreciate it,  :D

 

I strongly suggest you get the inlet manifold off and clean inside it and the inlet ports as well.  Just make sure no muck gets down into the engine.  You will probably need new manifold gaskets to ensure a good seal.  Use Carb cleaner and wear rubber gloves, no kidding. (Yes will do)

 

Check the air filter element is not clogged. (Done, I replaced it with k&n panel)

 

Check all the hoses between the turbo and the inlet manifold in case any are leaking and losing your turbo boost pressure. (cant see anything obvious)

 

Check that the outside of the intercooler is not blocked by dirt and debris.  If it is not cooling the inlet air, it will be robbing you of power. (Done)

 

Get some fuel system cleaner like PowerEnhancer.  This cleans the injectors, fuel pump, and combustion chambers and costs about £20 when on offer.  Make sure you follow the instructions fully.  Birmingham Audi are doing an offer at the moment for something similar for £15. (Got some red x, will fill the tank with super juice and use that)

 

Or you could try TerraClean (instead of PowerEnhancer), which is like a power washer that cleans inside the engine's combustion chambers.  Expensive at about £70 or more a go. (may try after red x treatment)

 

Start using a good fuel like Shell VPower that continues cleaning the fuel system after the PowerEnhancer has done its job.  Use it exclusively for the first month then one fill-up in every four or five to keep the muck from building up. (will do)

 

Take off the catalytic converter, turn it upside down and thump it fairy gently to loosen and remove the built-up soot inside it, then put it back on.  This reduces the resistance to the exhaust gas flow. (I didn't know I could! lol, any how-to?)

 

There might be blow-by around the piston rings, losing pressure and therefore losing power. (what is blow by? )

 

There might be a leak from the cylinder head gasket, also losing pressure and therefore losing power. (will have checked)

 

Have the fuel pump checked to see if it is giving enough pressure to get the right amount of fuel through the injectors. (will have checked, would this show up on vagcom?)

 

Have the injectors checked to ensure they are working properly. (will do)

 

Thanks again! :D 

Hi Ash,

 

Thanks for the good wishes!

 

I've had the Cat off a Mondeo 2.2 TDCi, but not off an Audi, so don't really know the details for your motor, sorry.  Generally, remove the heat shield above the turbo, remove the heat shields from the cat itself, remove the exhaust, unbolt the cat from the turbo, and remove the cat.  Maybe best to leave this one.

 

Blow-by is when some of the expanding gases that should force the pistons down are wasted because the piston rings don't seal properly against the inside of the cylinders, letting some gases blow by the piston instead of pushing it and providing power.

 

Yes, Vagcom should show up faults in the fuel pump

 

Some people find that K&N filters actually reduce the engine power because they draw warm air from inside the engine bay instead of cold air that the standard air filter setup uses.

 

Best of luck!

Great stuff cheers,

I just though of another reason for low power: inlet / exhaust valves not sealing.

 

If you get the cylinders compression tested, then this will show up the possibility of leaks from poorly seating valves, worn/damaged piston rings or leaking head gasket.  

 

It won't say which of the above is causing the problem, though.

Cheers!