I have an intermitent boost/power problem in my 2001S4 that has been driving me (and my mechanic) nuts. Looking for any suggestions any might have. It started several months ago and seemd to kick in when the oil temp was near its max (one notch shy of 250). Normally - with the APR chip I can push anywhere from 12-16 lbs of boost (as told to me by my vent mounted AWE boost guage). But when this problem occurs it will top out at only 6 PSI! Probably robs me of 100hp! Its very frustrating - sometimes it will bounce back - other times it sticks on this. Lately its been more commonplace and can occur even when the car is not fully heated up. My mechanic has already replaced a vacume control valve which seems to have somewhat - but not entirely cured some surging I've also been having - but no real effect on the boost issue. Additionally - I'm getting error codes - lot sof them. Related to overboosts in nearly all cylinders and relating to the exhaust (temp? not sure - we're wondering if these sensors are shutting boost down perhaps? saying its too hot?). My mechanic has consulted with other mechanics and seems to think its my chip (APR). He wants to replace it with a GIAC. I don't want to do this just to do it (this car is already costing me more $ then I would like - and I might detail another problem I'm having with it - and with Audi - here shortly). Any suggestions? Has anyone heard of this type of problem before? Any help would be appreciated.

 

Hi Dude,

Yeah, having similar prob with my Audi S3 Quattro. Brolem began before i had my car chipped so i doubt it is that. Going to my local Audi dealer today though to check my fault codes on VAG. Previous times it showed my Lambda Sensor behind the cat was faulty. Replaced that yesterday and still issues. However i must admit my problems seemed to have started after i fitted my atmospheric dump valve. Not sure if this is teh cause but will keep you posted later today once ive seen the latest fault codes.

Good luck mate...

Share the fustration and $$$$ lossss....

Later

 

Yes I hear you...thanks for the reply - keep me posted. Funny thing - except for a very brief period of low boost - it ran great all week...whose to figure...though I think with warmer weather my problems will be back. I really do think its a heat or heat sensor related issue - where something is telling the ECU that there is an (overheat) problem of some sort and its cutting back the power....

 

what are the exact codes? We need them to diagnose the problem.

 

I will find out and get back to you. Thanks.

 

Seem to have found the problem, In the turbo there is a temp sensor fitted. Mine is faulty an di am waiting for spares to arrive from Germany. When i connct ti the VAG and clear errors, car goes back to normal again. Give it a shot might be the problem. Also are you running a diverter valve or atmospheric?, external causes all sorts of issues.

 

Hi,

Just found some info regarding strange boost behaviour whilst logging from VAG on a test drive, fuel injection drops alot. After checking seems to be a fuel pump problem. Issue is aggrevated when temp increases as this allows for dirt particles to disolve and clogg the pump. Check it out.

 

Madiba - thanks for the input - I'll check it out - though I'm not clear if your problem is just fuel injection or a temp sensor in the turbo (error code for this?) or both....BTW I've got Forge or Baily DVs (forgot which I ended up putting in)....Car behavior seems basically the same with check engine lite on then when error codes are cleared.

Here are my error codes (at least some of them - may have a few more...)- P1454 (EGT Sensor 1), P0300 (Multiple cylinder misfire), P0305/6 - cylinder 5 & 6 misfire, P1555 (charge pressure/N75? valve), P1462 (#1 misfire), P1786 (EGT sensor ?)

Though my problem is intermitent it seems to occur more frequently when it is warmer out (in this case over about 45 deg) - performs better when near freezing out... also if I am running OK and I stop for gas - or make a short stop - like at a 7-11 or such - or if I am sitting in some stop and go traffic - invariably after - my boost is capped. I've also noticed some roughness (like cylinder misfires perhaps) occasionally at about 4200 RPM...when this occurs it seems as if my boost caps out shortly thereafter. Sometimes I can get the boost back by stomping on the gas hard about 3 times in a row - as if something is freeing up (like maybe the fuel pump is clogged?) - then it might be fine for the rest of the trip or then it might be fine for a few runs then cap back at 6000 boost...madening I tell you!

Any suggestions/help is appreciated. I'm not a mechanic - so I don't do my own work - but I'll likley be takin git back into a local performance shop in a few weeks.

 

Hi,

Had very similar problem over the weks and landed up spending a small fortune trying to find the problem. He is the story, chipped my car and put on external DV despite various advice about this. Started getting strange jerking from time to time. Also picked up misfire errors as well as boost errors etc..

Solved these one by one as follows:

Jerking problem --- changed fuel filter, could not even blow a little air thorugh old one.
Misfire error ----- all four coil needed to be changed and changed spark plugs while at it
Boost error ------ came from 2 areas, 1 chip and 2nd DV.
Now here is something i discovered and is proven fact, many will advise that Audi designed turbo to dump back into the system and this is true and the reason is firstly it keeps the air mass metre happy so fuel mixture is 100%, secondly the boost helps keep turbo blades spinning so when you put your foot down the turbo spools up quicker.
However this is all fair a well if you are boosting according to standard spec. This being around 0.7 - 0.8 bar depending on gear you in. So the system can only handle 0.8 of boost pressure being thrown back in. So if you are chipped and you are, you need to check the following, who developed you map and how much boost are you pushing ? The extra boost beyond 0.8 bar needs to be thrown out the system (external DV). So you need to change your DV to a dual unit that dumps back in to the system at all times and if the car is pushed, excess boost is dumped externally.

I am not sure where you are based and what is avail to youin such form in your country but a good unit i have successfully implemented is a unit from "Turbosmart" in Austrailia. In fact they have specifically developed these vaves for Golfs and Audi's. Their website URL is www.turbosmart.com.au check it out and find your local distributor or have one posted to you.

Then once i had done all this i was still having boosting issues, thsi was 2 things, my Lambda sensor was gone as well as my EGT sensor. Finally the last thing or first thing maybe in your case is change your fuel pressure regulator. These cars have 3 bar fuel pressure regulators and a 5 bar fuel pump. Now the pump is sufficient but the regulator drops the fuel pressure. Go and buy yourself a 5 bar high pressure reg and have it installed. You cannot believe the diff but simple really if you think about it. Chip telling car to boost more, computer telling car to add more fuel but at the end of the day regulator having final control over the fuel feed. So more boost = more fuel. This solved my inconsistant boost problems once and for all. Car is runnign soooooo smooth.

In fact currently pushing 205 kw out of my standrad S3 and K04 turbo and droped 0-60mph to 5.7 sec....awesome!!!

Hope this helps, by the way check out this website about the fuel issue, these boys have gone over the top but really know what their doing... www.dahlbackracing.se

Later


Waiman

 

Hey Madiba - thanks again....hardly know where to begin. One thing though is that I have operated without this problem (and with chip and UG DVs etc) without a problem for 2 years before I suddenly started having these issues. But perhaps it is a combionation of things. Heat defintly seems to be a factor - its been cold here lately and the car has been runnign great. But even then - I stop for gas - and when I start back up again - and for the rest of the trip - my boost is curtailed again. Thanks for all yoru suggestions though - gives me at least something to go on. I plan on taking the car in to my mechanic (local performance shop) - very soon - and I'll discuss with them what to check out first and we'll see...I still think its goign to cost me $$$ regardless...but I want it fixed thats all - if I'm spending the dough...