Audi A4 1.9 TDI (1999) - power loss...limp mode?

[accy]

Had a similar problem to yours a while back, took it to a garage where the boost pressure sensor was changed, been perfect since

[obladeo]

Hi chap just looked at this thread and though one or two things.

You said you had a full service. One question is did you check to make sure that they had changed everything?

The reason i work on my own cars is that garages are there to make money. They say they have done something but they haven't. My uncle is an amazing machanic and he was telling me allot of the things they do (it's amazing trust me).

The reason a car will run crap is either air or fuel (sometimes the brian(ecu) but norm).

Check to make sure theses have been replaced in your service (they should look new)
Air filter (you can check this by hand as it only 4 clips)
Fuel filter just look at it should look new and shiney
May sound strange but check your oil filter is new and also your oil level is right as some cars monitor this and go limp.
best way to do this is to first
Clean the system out which everyone should do before and mot. Just sit and rev your engine untill all the crap has gone out the system
Next take your car on a quick run and then check the levels (let car cool for 5 mins).

Next is to check the sensors which is never good. Find all the sensors on your car and take them off and give the a good clean. Depending of the sensor user either wd40 or gt85 and a cloth to clean em.

The exhaust sensor cannot be checked if your car has one as it's inside a steal case. You will just need to replace it.

hope this helps if not just tell me to bugger off lol

[k3t4n]

thanks accy. Can you advise where the boost pressure sensor is located? Is this the MAP sensor you are referring to? I'm not too familiar with the location of these in the engine bay.

cheers

[k3t4n]

hey obladeo,

firstly many thanks for the long reply. I will definitely check out the things you mentioned. The car has been running better since I took it to the garage to get the turbo cleaned. I can get to 80mph and theres not much in the way of resistance. Assuming here that the garage did actually do the clean, as I supplied the Innotec turbo clean kit (£40) although I noted the bolts I couldnt get off the exhaust manifold where it joins to the turbo inlet are still v tight.

when driving in town or on the motorway though, it still feels flat through the gears, so guessing im still in limp mode, as the boost isnt all there, although I can feel some but not like how it was before. the chap before mentioned the boost pressure sensor. do you have any experience of cleaning/changing these? where are they located? Ive read on the forum that its sometimes the MAP sensor thats knackered, but I dont really want to spend until I know thats the problem.

appreciate your help so far

[mrp0ny]

Hi Guys

I have 2 x A6 1.9tdi's one with 413K on it on original engine, gearbox and turbo etc.

The Limp mode problem could be EGR, MAF sensor or especially the vacuum pipes (little thin pipes) on the left hand side as you open the bonnet. Basically the computer thinks there is too much fuel coming (incorrectly) and shuts it down to avoid damage. The other thing it could be is an incorrect ECU.

Just a few ideas....

David

[k3t4n]

Where is the EGR valve located? Is there any way I can clean it? Do I need to take it off to do so? Also, I have noticed a constant 'hissing' sound when accelerating...I dont recall this happening when I bought the car a few years back. Sounds like a boost leak but I could be wrong. Any ideas? p.s I bought a VAGCOM cable so I can connect to my laptop, but no error comes come up under the Engine tab.

[paddy006]

check all your hoses for leaks.
i had a simular problem that ended up being a tear in the rubber coupling that connects the pressure pipe to the egr manifold.

[yuley]

Hi, i'm having the same trouble on my 1.9tdi awx, it's really been ******* me off i've changed the maf sensor to no avail i've had it diagnosed on a new snap on diagnostic machine which brought up fault code 17965, basicly it's boost regulation pressure exceeded. The diagnostic machine gave me the reason for this which is a loose pipe or a tear in one, i've been told to check the main boost pipe which leads from the intercooler as this was the cause of someone elsses problem i've checked this and the fit isn't as snug as should be so i've ordered a new one from audi £45 i'm gonna fit this and hopefully it will do the trick, also gonna check vacuum pipes as mrp0ny say's above. Hope you get it sorted an post if you do cos i'm getting sick of it now, and never mind micras i got overtaken by 2 old dears in a fiat punto oh the shame..... a4 tdi 170bhp!!!!

[k3t4n]

ok just an update...

I am now able to get past 80 mph, but not as effortlessly as it used to be, saying that, I tried using electrical insulation tape on a couple of the thin vacuum pipes, as the braid is absolutely knackered on the ends, and the taping ensures that the pipes dont expand as much, so hopefully the pressure stays when driving or overtaking, ie, when more boost required.

I've noticed a slight difference, and the car feels slightly more responsive, but as these vacuum pipes are worn,and since the small difference has been felt since using the tape method, replacing these is prob the first thing ill do. I've been thinking it could be a MAP sensor, 02, etc. If that was the case, surely I'd have smoke blowing out my exhaust? havent seen any smoke now since the turbo clean, and its the same even if I floor it from 60-80 in 5th gear. I would like to get to the bottom of it, and hopefully restore the power, as the 'redeye' 110bhp model i have is certainly quick enough overtaking and the weight of the chassis combo with engine, plus the koni suspension ive added (done around a year ago-STR kit 35mm drop all round) makes this car very agile in its class.

Just one thing ive noticed, theres a plastic ball type thing located in the left hand side of the engine bay, a little way down into the engine bay, and the vac lines run into this and the braid is v frayed. Do I just pull the end off the ball to replace? Or does that require me to remove the ball thing as well? any help here would be most appreciated. thanks

[yuley]

Right i've now sorted my problem, it ended up being the boost sensor on the boost pipe at the rear of the engine i also replaced the n75 selaniod which didn't make any difference so i would try the sensor on the rear boost pipes if i was you, hope you sort it out... n75 selaniod £29 and boost sensor £49 from audi..