[s-cars] Drastic Power Loss - Loong

Thu Sep 20 11:18:40 PDT 2007

Coolant Temp Sensor in back of the block?  White two pin.  Prolly not but
just a few bucks and 5 minutes to replace it.

Mark

-----Original Message-----
From: s-car-list-bounces at audifans.com
[mailto:s-car-list-bounces at audifans.com] On Behalf Of
manuelsanchez at starpower.net
Sent: Thursday, September 20, 2007 9:50 AM
To: s-car-list at audifans.com
Subject: [s-cars] Drastic Power Loss - Loong

This didn't post before, so sorry if it's duplicated

S-Heads,

I’ve run out of idea’s and I’m desperately seeking some insight into a power
problem I am having, thus the looong explanation below. I hope some of you
can take the few minutes to read this post and help me find the stupid thing
I seem to be missing.

Problem:
Drastic Power Cut Out (neck snapping forward kinda cut out) at peak boost
(We suspected intake leak but can’t find one, at least not yet).
Around town driving is OK. Car generally does not feel as though it’s making
as much power as it used to (confirmed by slower lap times at Driving School
Events, and not being able to dust Bro-In-Law like I used to at previous
events, and no he can’t possibly be getting better at a faster rate than I
am )

I’ve had the MRC software and RS2 bits on for about 3 years.

I can build boost to about 27 psi (my gauge only reads to 25, so I am
estimating based on the travel distance of the needle), in say a 2nd or 3rd
gear pull and slightly after reaching it, 27 psi, it will feel like someone
thru the Queen Mary’s anchor out of the tail gate, if I back of slightly on
the throttle, the power will come back on and I can try to build boost
again.

When the engine is relatively cold (i.e. it has not reached the big hash
mark indicating normal operating temp) this problem does not always occur.
So I can hit 27 psi without the big cut out. I know I shouldn’t be boosting
it like that before the oil is warm, but I’m desperate at this point to try
and find out what the problem is. Seemingly after reaching normal temp (and
it will stay at normal temp once there, just fine) I am now getting this new
power cut off.

Previous to this drastic power cut-off, the car hadn’t felt like it’s had
all the power it used to have. I would be able to build boost, even to these
peak 27 psi levels, but it wouldn’t feel like it wasn’t pulling as hard as
it could be or used to be. It didn't used to cut off like this.

So what did I change between the time it didn’t feel like it was running as
strong as it could be, and when I would experience this drastic power cut
off? These things:

Injectors (swapped the Racetronix 37 lb/hr units with 034’s RS2 clone
injectors, I was trying to resolve that niggly check engine light that would
flash on and off with this injector / software set-up. I believe others have
solved this issue by installing the 034 RS2 clone injectors, funny thing
was, it didn’t seemingly solve the check engine light problem for me that
would occur on very very light throttle)
Replaced Stromung Test Pipe with Stromung Cat section
Replaced Oxygen Sensor (the one I replaced was only a year old, but I
thought with new injectors, why not)
Installed Fuel Pressure Gauge

With the exception of the Stromung Test Pipe, I swapped all the old bits
back in, and I still have the problem (this included removing the Fuel
Pressure Gauge). (Could it really be the Cat?, I’ve never mounted this Cat
before, it was brand spankin new, and I drove the car around with the Cat
and the Racetronix injectors for only about 100 miles before swapping in the
slightly smaller 034 RS2 clone injectors.

Patient:
95.5 UrS6A-125,000 miles
RS2 Turbo
RS2  EM
Mihnea Custom Chipset
Stock MAF (although also tested with a new RS2 MAF, same result),
Racetronix 37lb/hr Injectors (Although also tested with 034EFI RS2 Clone
Injectors)
Tom and Marc FMIC
SAMCO Boost Hoses everywhere else
Stromung Exhaust
Forge 007 By Pass Valve
RS2 WGFV
Original Wastegate
034 DIS Coil System with new Ignition Wires
New Plugs (Bosch Tri-Electrode Copper Plugs from 034, the kind they use on
their monster motors)
044 Fuel Pump
Newer Fuel Filter (2,000 miles)
New Fuel Pressure Gauge
New Adjustable Fuel Pressure Regulator set at 56 psi – 3.8 Bar (idle) (Is it
supposed to be 4 bar for RS2, and if so would 2 PSI really make that much of
a difference?)
VDO Boost Gauge
Original CPS (no trouble starting when hot)
I've had Leakdown and Compression tests yielding acceptable levels

I’m hoping the list wisdom can help with this one.

We have suspected of course a boost leak, but have not found one.

Pressure Tests of the Intake Tract:

We have pressure tested the system just south of the MAF, by pressurizing
that first hose that isn’t supposed to be pressurized and plugging the Idle
Control Valve, Throttle Body, and the Crankcase Ventilation line on the
turbo side of the engine, at the front of the head. There was not a big leak
by any means, but we did notice that the swelling of that first hose, the
MAF to turbo hose, would visibly reduce in a few seconds. I have tried
pressurizing the system with the ISV and T-Body hoses connected, to see if
those various bits of rubber pieces located under the Throttle body had torn
(I replaced all those pieces last year), but no audible leaks.

We have also tested the system just south of the turbo outlet, we have
blanked off/plugged the Idle Control Valve, Throttle body and the crankcase
ventilation line there on the turbo side of the engine. We have tried
testing with the Idle Control Valve and the Throttle body connected. No
audible leaks.

Checked Moisture Trap (located at ECU in S6) – OK

Flipped BPV connections around-no leak or seeming effect

Swapped my BPV with another BPV – no leak (We have not tried running the car
with this other BPV though, don't know if this would make a difference)

ECU's
I have swapped in a different stock ECU with stock chips and pressure
transducer, as well as swapping in my original stock injectors from my
pre-RS2 upgrade. Near peak boost for stock levels, I am getting this same
drastic power cut-off, say around 13 psi.

So I somehow think both my ECU with RS2 software and a completely different
stock ECU are “seeing” something similar, and throwing out the Queen Mary’s
boat anchor.

What we don’t think it is:

Ignition
Well, it’s a new 034 DIS System, with plugs only a few hundred miles old. We
haven’t looked at the plugs this week, but we did look at them when I
installed the DIS system several months ago. At the time I had the stock
Bosch F5DPOR plugs. There was a slight grey/white residue at the tips, which
I think is indicative of a lean condition, which is odd because MRC software
is supposed to run rich. I swapped plugs because there was a slight crack in
the ceramic housing one one of the plugs.
I ran the car at a dyno day about 6-9 months ago, and they told me the car
was running waaay too rich. Off the top of my head I can’t remember the A/F
ratio at the dyno day. I just love the seemingly contradictory indicators.

Knock Sensors
The mechanic who has serviced this car since I’ve had it doesn’t think it
would be knock sensors for a couple of reasons(which I don’t know enough
about how they work to form an opinion, I guess I could say that about a lot
of these issues):
    He thinks they would throw a code if they sensed something, and he
hasn’t seen a code related to these
   He doesn’t think it would build up this amount of boost if there was
knock

Fuel
I’ve got an 044 pump in there (3 months ago), new filter, adjustable fuel
pressure regulator set to 56psi at idle (which I think is 3.8 bar) and a
fuel pressure gauge. There was some chatter about someone running RS2
software and a stock pump, but not getting enough pressure at the rail, so
since I needed a new pump I figured I’d go hog wild. Anyone know if 2 psi (
0.14 bar) at idle is enough to throw things out of whack? I think RS2
pressure is supposed to be 4 bar but I’m not sure.

The gauge is mounted in the engine compartment, so I can’t see the pressure
under load. I suppose we could try to rig something so I can tape it to the
windshield while driving to keep an eye on it. Anyone know what range in Psi
I should see while under load or at full throttle with the pedal buried
against the firewall? I assume it's not supposed to be a continuous
pressure, but rather a variable one within some unknown to me limits, yesh?

Codes:
We have seen a few codes thrown. Whether or not they have anything to do
with the loss of power or drastic power cut-off is the $64,000 question.

They are: 
00537 – Oxygen Sensor Control
Maximum Control Level Exceeded
Condition:
Fuel Tank Low resulting in fuel system pressure less than 3.3 bar (48 psi)
[Note tank was ¾ full as indicated on fuel gauge]
Ignition System Failure
Symptom:
CO before 3 way catalytic converter less than 0.5% (Hmmm, what could this
mean???)
Fuel Consumption high

Repair:
Fill Fuel Tank (tank had plenty of gas, and fuel gauge reads accurately)
00537 – Oxygen Sensor Control
Minimum Control Limit Exceeded
Condition:
Engine Intake Air Leak after Mass Air Flow Sensor-G-70
Leak in Exhaust System in front of 3 way catalytic converter
Heated Oxygen Sensor (HO2S)-G39-malfunctioning
Fuel System Pressure greater than 4 bar (58 psi) [This is interesting, seems
like I will throw this code all the time if I set the Fuel Pressure to 4
Bar/58 psi, which is what I believe I’ve been told is the Fuel Pressure for
RS2’d cars. True?]
Symptom:
Rich Exhaust
Spark Plug Fouling
CO before 3 way catalytic converter greater than 3%

Repair:
Repair Leak
Check HO2S-G39
Check Fuel System Pressure
00561-Mixture Adjustment
Adaptation Limit (mul) exceeded
Condition:
Fuel System Pressure too low
Spark Plugs, ignition coil, ignition coil power output stage malfunctioning
Symptom:
Reduced Fuel Economy (no kidding)
Sooty Exhaust (yeah, in spades)
Repair:
Fill Fuel Tank
Repair Leakage
Check Fuel System
Check Fuel System Pressure
Check G70 (Mass Air Flow Sensor) [We cleaned the OEM MAF with MAF Cleaner,
and we also installed a brand new RS2 MAF-we still had the drastic engine
cut-off]

I’m not a mechanic(and I don’t play one on TV either), but I somehow think
the ECU is seeing something it doesn’t like (duh). A few months back I
surmised that since I was seeing plenty of boost on my gauge, but the car
didn’t seem to be moving quite fast enough, the ECU must be retarding the
timing for some reason. Now it must really not like what it’s seeing, and
it’s throwing the big anchor out the back. SO , assuming it’s the ECU trying
to save my motor,  what kinds of things would cause the it to back off like
that? I thought maybe knock, but my wrench says knock would throw a code
(true?, what say ye?). Dyno guy says A/F is very rich, plugs had a little
bit of white/grey deposits on the tips. Nuts.

This has been really frustrating and we are running out of ideas. Any help
is greatly appreciated.

Thanks for reading.

-Manny

95.5 UrS6 Avant (kickin my arse)
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