Aus s3 help

[3v0LuTi0n]

Hey Guys and Girls,

I'm a new S3 owner and I think I'm in a spot of troubleshooting hell, I don't know which way to head in my theory of this cars operation, the symptoms I'm getting are:
Rough cold starting problem, overfuelling on cold start, takes about 2 primes of fuel pump to start
boost gauge reading -12inHG for approx 2 mins, idle at 1350-1250rpm, then goes to -20inHG and idle is at 810rpm (a/c on)
hesitation on driving in this time (i know, just wait 2 mins right, although didn't have to on my Nissan 32GTR or Lancer Evo 8)

I bought this awesome little car about a year and a bit ago, but since there was no history with it, it was a bit of a risk, but you couldn't go wrong with an audi right? I've had to do countless repairs which includes replacement of the engine due to the big end bearings failing due to excessive high boost pressure & poor maintenance @160k kms which is unheard of from anyone right?

The modifications it came with when I bought it were:
Forge 007 DV
Forge TIP
Forge Boost Piping
Manual Boost Controller
FMIC
Modified cold air intake to Air Filter with K&N filter
Full exhaust system
Boost set at 19PSI, standard 8.6 PSI
APR stage 1 tune

So far I have replaced:
BAM engine
all lifters
Oil pump & pick up
Upper Cam chain tensioner
Cam cover gaskets
Clutch & Flywheel
n75j to f model
multiple vacuum pipes
timing belt
tensioner, rollers, bearings
water pump (metal impeller)
thermostat & elbow
expansion tank
Fuel Filter
Plugs
Oil filter & oil every 5k

Now things are starting to frustrate me, on these cold starts, could it be a MAF sensor, running rich etc or the coolant temp sensor not reading correctly, until the temperature comes up a bit, bad 02 sensor, or a blocked PCV valve/breather system fault/leak

I'm an Aircraft mechanical technician and not afraid to leap into something but for all the things I've done or had done already, I thought she'd be banging like a champ by now.

any help or advice on what to do next would be greatly appreciated,

thanks guys

3v0

 

[3v0LuTi0n]

Update:
Have replaced majority of PCV system, found the vacuum pump to be blocked, pcv jammed open and purge valve had 2 holes in it along with associated holes in the piping under the manifold.

cleaned maf sensor, was as black as the ace of spades!

cleaned inlet manifold sensors, one directly behind throttle body (had crap caked on) & one at intake, both filthy, maf cleaner works well haha.

Idles at 1250 now for warm up with -14inhg vacuum then once temp comes up a bit it goes to -20inhg & idle drops to 800 with minor fluctuations in vacuum (i'm talking minuscule here) with idle just barely bobbing. Would there be a vacuum leak at brake booster where pcv system goes to, when I pump the brake pedal, the vacuum drops and then comes back up, about as low as -14inhg when idling but only if i ferociously pump it.

thermofans aren't kicking in at high speed and only at low speed, its got a/c gas and all, compressor kicks in, fans come on low but but compressor turns off after about a minute, either high pressure switch (anyone know where its located? also is there a check valve in it?) or i was thinking along the lines of fan control module for the fix. It gets above 35 degrees C here some days and normal temp is about 15-25 and dont want to be caught out in a 45 degree day...

any help guys would be greatly appreciated, even if someone were to point me in the right direction that would be great, most mechanics around here charge 150-250 per hour for labour don't care if they fix it or not.

cheers

3v0

 

[<tuffty/>]

1.8t's don't have the smoothest idle in the world so bobbing about is normal... its plausible for the brake servo line to have a vac leak but this is typically in the 'V' shaped hose coming off the end of the inlet mani on facelift S3's... prefacelift doesn't have this 'V' hose though (no idea what year your car is)... the check valve for the servo is pretty much where the servo is wrapped in a small heat blanket... the pipe is plastic is subject to heat and can split... check that..

Fans... low speed kicks in around 96/97 degrees with aircon off (monitor with VCDS)... high speed around 100+ degrees (can't remember the exact figure)...

Aircon pressure switch is behind the alloy heatshielding on the bulkhead

<tuffty/>

 

[3v0LuTi0n]

Hey thanks for taking the time to read and providing the info Tuffty!

Ah thats good to know mate, at least I'm not going crazy, was thinking that it would be rock solid, thanks to your wisdom, I've been following your posts and info for a while now lol.

Its a 12/2002 s3, I found that v shaped pipe cracked early on and replaced it with some silicone piping, along with rebuilding the PCV system the other night a week after the engine was replaced, not that all the sludge from the previous engine was picked up by the local mechanic.

Ah excellent, they're doing that, smaller fan comes on first without aircon on, it doesn't get anywhere near the 96/97 very often as I've had all the coolant and everything purged, radiator cleaned, along with replacing the thermostat & associated plumbing as I wanted to be sure that it had no plastic stuff in it from any previous plastic water pumps, after I installed a metal one.

Oh great, sounds like an engine out job, there isn't much room to get at behind the engine itself, which side by chance? is it near the high pressure port on the left hand side of the engine bay or near the brake master cylinder?

Oh sweet, I'll look into that tomorrow before I start work, is that line that runs to the brake servo that goes over the brake fluid reservoir just go down past it then right angle into it?

in your experience, would you believe the high pressure switch to be at fault? Aircon system sucks to troubleshoot...

Cheers for the info again mate, love your work!

3v0

 

[<tuffty/>]

Won't need to take the engine out for the pressure switch... just remove the charge pipe and the heatshield is held on with a few screws..

Best pics I could find from my build...

The switch location.... you can see it hanging off the alloy pipe going across the top of the bulkhead

Heatshield...

You should be able to get to it easy enough with the charge pipe off

I have no experience of aircon in that context... have you scanned with VCDS for fault codes? that would be a start point

You should also check the three 30A fuses in the fuse box on the battery as they have a habit of corroding and can cause issues like this..

<tuffty/>

 

[IPG]

Won't need to take the engine out for the pressure switch... just remove the charge pipe and the heatshield is held on with a few screws..

Best pics I could find from my build...

The switch location.... you can see it hanging off the alloy pipe going across the top of the bulkhead

whoa. melted cam cover?!

 

[<tuffty/>]

whoa. melted cam cover?!

It's a spare one of Bills being used on the build engine I had in the bay at the time... it was dropped by a courier and repaired...

<tuffty/>

 

[3v0LuTi0n]

Awesome, just awesome, thanks so much mate!

The pics really help, I thought it would be buried down in behind the airbox or something... at least its easy to get behind there with that heatshield off. At least then I can shoot the wires to see if either them or the switch is faulty.

Yeah I did a scan with it but the system keeps having comm errors with the controller... looks like i'll be pulling that out and giving the wiring a good once over...

Although I did get a P16502 - G62 sensor reading too high fault on the list so I have replaced the coolant temp switch on spec to be sure and kablam, cold start issue fixed!! Driving home from work at 2am definitely tested that out lol (mind you the PCV system probably helped along with replacing all the plumbing and FPR in there!)

But now I think my dogbone engine mount has self destructed due to the engine change, everytime I take off from a standstill, theres a clunk, at first I thought it was my clutch but ruled that out just by slipping it into gear. yet another thing on the replacement list... could it also be low gearbox oil and the clutchpacks in the LSD grabbing or am I barking up the wrong tree?

And yeah, wow melted cam cover!!! was that heat from too much boost from that epic sized turbo you run?!?

Again, thanks guys for your plethora of info on this little car.

Hope you all have an awesome weekend!

3v0

 

[3v0LuTi0n]

Oh Also, the three 30A fuses are all in tact, that was my first port of call...

Thanks again mate

3v0

 

[3v0LuTi0n]

Hey Guys & Gals,

Sorry for the late reply to all posted here, Thanks so much for all the helping in attempting to test & troubleshoot the symptoms I was facing!

I ended up testing the compressor and found it was the original one and had seized up internally on its mechanical valve which allows gas flow through the compressor, so out with the old and in with the new and hey, presto, instant cold air once it was regassed!

Changed out the coolant temp sensor also just for troubleshooting sake and considering the age of the vehicle also. No longer an issue and scanned with VAG-COM (hey yes I bought one) and found that its no longer there, something worked lol.

I ended up replacing the dog bone engine mount and as a lot of people have found out, there is more vibration through the cabin now due to the stability of the new mount, and best thing, no more engine movement and clunking from the dog bone contacting the subframe. How good!

Last but not least, the cold start issue, fuel issue, whichever it may turn out to be. I have done extensive testing & troubleshooting on this system and I am at a loss, I have heaps of fuel pressure, starts first time every time once warm, do I change the pump due to a check valve that may or may not be working, or start with the solenoid and go from there?

Tuffty, I'm looking to your guidance here as you seem to be the wizard when it comes to these cars!

With the Activated Charcoal Solenoid (n80), I found that its open on cold start and seems to take about 3 mins to close, which makes the car run really rough & undriveable due to the loss of vacuum in the system but once its closed, the car runs sweet, I can actually watch the boost gauge and see the valve close. This only happens on days where the vehicle is cold & the outside temp is about 5-15 degrees C, and random days that it feels like doing. What could be causing this?

Cheers guys for all the help so far!

Your combined knowledge is greatly appreciated as we don't get much help here in Aus with these cars from the manufacturer

3v0