Yet another problem!

[OllieH]

Only just fixed the coilpack problem I had on the weekend and now I've got another fault! It actually appeared as soon as I fitted the new coil pack and took the car for a test drive. The misfire had gone but the idle is still crappy, hunting up and down very slightly and coughing occasionally. The main problem though is when I accelerate I don't get any real power until above 3k revs, whereas before I used to get progressive power from 2.5k onwards. I thought at first it might just be in my head, but now I'm certain that it's not as it was. When I floor it in 3rd I can hear the screech (for want of a better word) of the turbo boosting up but the car doesn't accelerate in proportion to it, and then all of a sudden at just over 3k revs the car takes off. It doesn't feel as fast as it used to aswell, but that may just be that I've got used to it?? Any ideas?

I disconnected the MAF earlier today to see if that made a difference but had no change. On a side note, when the maf was disconnected the ESP light lit up continously?! Should it not be the CEL?

I need to replace the battery aswell, but can't see this causing it. I will also be changing the DV this week from the Split-R to the 007P. Could a faulty DV be causing this? although it only appears to be dumping when changing gear.

Any help is appreciated. I've decided that I'm gonna purchase VCDS, but in the meantime I want to try and sort this as it's making me feel like I don't want to drive the car in fear of causing more problems.

 

[<tuffty/>]

Idle issue sounds like a vaccum leak... would be the first thing to look for at least...

If you have had your car mapped then the screech could well be cavitation which is common on remapped S3's... If your car isn't mapped then it could well be a boost leak.

ESP light does come on to indicate a fault in the MAF for some reason... no idea why but it does...

A Spilt R isn't going to help the way the car runs as it is effectively leaking out air the MAF has already measured... the outcome of this will be the engine will run momentarily rich after its dumped air... wether this is contributing to your idle problem I don't know but it won't help in normal running...

Check for spilt/damaged pipes under and around the inlet manifold and check the tightness of the hose clips on the charge system.

<tuffty/>

 

[OllieH]

The car is mapped and I'm aware the screech noise is normal, it's just normally when it starts making the noise the car accelerates hard, but now I'm hearing the noise and there is a 500+ rpm delay. When I fit the DV I'll have a good look around at the other areas you said. Cheers tuffty.

 

[OllieH]

Update:

I have now changed the DV to a 007P but I still have the same problem where the engine doesn't seem to be boosting properly at the normal 2.5k, and the power doesn't kick in until 3k revs. I have just bought a VCDS cable from Nigel on here and have done a log run on blocks 115 and 120 in 4th gear and the actual boost is lagging the requested by quite abit, although being a novice I'm not too sure what I'm meant to see. Not sure how to post an excel document on here but I have managed to snip the graphs:

What's confusing is it does make full boost eventually, so I can't see there being a pipe blown off, so why would it lag behind like that? Could it be something to do with the actuator and N75?? No DTC's are showing for the engine either.

Any help is appreciated, as I'm a novice when it comes to turbo'd engines.

Just to add, I also took off the PCV? (black circular mushroom looking thing) and gave it a clean, and was able to blow air through both ways. Is it meant to do that?

 

[<tuffty/>]

The bit you took off (mushroom) is one part of the PCV, the rubber pipes etc here do go soft but are not under pressure...

Bits to check... under the inlet mani in the middle there is an 'L' shaped pipe that splits at the elbow and will give boost and vacuum leaks... this is connected to the 'Y' shaped plastic one way valve. The rubber pipe coming off this and going to the engine block part of the PCV splits underneath where oil collects and pipe goes soft... you need to look close to fine this one...

All the plastic pipes hangin off this are prone to cracking where they are pushed on to the various connectors and create boost/vac leaks... the 'V' shaped pipe coming off the end of the inlet mani split on the inside of the 'V' and under the clips...

I removed most of mine replacing bits with appropriate size silicon hose.

See my build thread for some ideas...

<tuffty/>

 

[OllieH]

Tried looking under the inlet manifold today at the parts you are on about tuffty, but couldn't undo the bolts that hold on the black plastic trim (the bit that has the dipstick tube through it). I think I'm gonna have to drill them and use a stud extractor. Couldn't see any splits from above though but will need to do a proper check. So a split on the PCV system can cause a problem with boost as well as affecting the idle?

I have just bought some 4mm internal diameter silicon pipes in preparation for finding some splits.

Do you agree that it's not normal for the actual boost to lag the requested that much? The only reason I ask is because I don't know whether it's normal or not, all I know is that I used to get power from 2.5k and since I changed the coilpack (as diagnosed by AMD) I don't get power till 3k.

 

[<tuffty/>]

Tried looking under the inlet manifold today at the parts you are on about tuffty, but couldn't undo the bolts that hold on the black plastic trim (the bit that has the dipstick tube through it). I think I'm gonna have to drill them and use a stud extractor....

They are a right pain... I bought new ones when I did my BT work and tried undoing them the other day and rounded it already... even with copper slip on the threads it still locked in tight!!!

...Couldn't see any splits from above though but will need to do a proper check. So a split on the PCV system can cause a problem with boost as well as affecting the idle?...

The PCV system shouldn't see boost at all as it would pressurise the the engine and blow out of any gap it could find... this is why the vacuum system is plastered with one way valves... If of course your engine bay is not covered in oil then they are working OK

The main pipes that will cause boost and vac leaks hang directly off the inlet mani... if they split before they hit a one way valve then they will cause boost and vac leaks... anything split after a one way valve will just cause vac leaks (idling probs, hesitation etc)

...Do you agree that it's not normal for the actual boost to lag the requested that much? The only reason I ask is because I don't know whether it's normal or not, all I know is that I used to get power from 2.5k and since I changed the coilpack (as diagnosed by AMD) I don't get power till 3k.

humm... difficult to say without doing logging of other blocks... boost/vac leaks could cause the slow spool... best bet is to sort that first and take it from there... you may notice the actual flatlines between around 2.9k rpm and 3.7k rpm... this is because its gone off scale for the MAP sensor (1.55 bar)... means that you are pro spiking around the 1.6bar reginon before the N75 brings it back into line at around 4.2k... Seems to hold against requested but starts to drop off a bit early (difficult to say as its been a while since I have seen a normal S3 power curve)... this may indicate a boost leak... boost will drop off anyway after around 5.5k as the K04 runs out of breath...

<tuffty/>

 

[OllieH]

Ok, cheers for that tuffty. Looks like it's gonna be a steep learning curve for me I'll make my next job checking all the vac lines coming off the inlet manifold and go from there. Just need to get myself some stud extractors first! I take it you reused all the non return valves on the PCV system, and just replaced all the rubber hoses?

 

[<tuffty/>]

I removed all the bits you see in the last pic... I replaced the 'L' shaped hose off the mani to the 'Y' shaped valve with silicon, left the PCV connection in place and removed all the hard pipe as it was cracked. I blocked off the other branch of the 'Y' valve that doubles back to feed the servo vacuum... this is the pipe that runs/joined above the 'V' shaped tube at the end of the mani.

As I had removed all the hard pipes that originally fed the servo vacuum and took the vacuum for the servo straight from the outlet at the end of the mani ditching the 'V' shaped pipe. The one way valve you see in the last pic that has the 'T' part blocked off is re-used in this feed to prevent boost from going into the servo.

<tuffty/>

 

[OllieH]

I'm sort of understanding what you mean there. One thing though, what is the servo you are referring to? Gonna have a look through your build thread now to see if I can learn some more.:icon_thumright:

 

[<tuffty/>]

Brake servo....

clicky --> http://en.wikipedia.org/wiki/Vacuum_servo

<tuffty/>

 

[OllieH]

I knew that, lol... No, honestly..... :icon_thumright:

 

[sportstractor]

intresting thats youv simplyfied your breather system tuffty, This inspired me to check mine, and Iv found 2 leaks, one pre and one post return valve. Just trying to figure out if I can simplfy it even more by venting crankcase to atmoshere with a high pipe and filter off the tee. Seems that it would be more trouble free in the long run, As crankcase gases only vent back into inlet just to conform with legislation i believe.

sorry for the highjack