[s-cars] Drastic Power Loss-So far No Joy

djdawson2 at aol.com djdawson2 at aol.com
Fri Sep 21 23:25:13 PDT 2007

I would suggest going back to basics.  Engines function due to the presence of 2 things... ignition and fuel.  For the engine to cut out as drastically as described, one of these two things must be failing.

I would do everything needed to watch your fuel pressure at the point of cut out.

On the other side of the fuel pressure topic, I have seen these FPRs fail on the side of full available pressure.  Too much pressure can result in overfueling to the extent that ignition is virtually extinguished.  With the amount of soot present, this may be a possible option to investigate.

You might want to try and observe your exhaust (rear view mirror) during full throttle.  If you see a fairly heavy black exhaust output prior to cut out, overfueling may be the issue.  If this is the case, I would try a stock FPR and test the results of the swap.

The idea of a test light attached to the FP circuit is also a good one... to determine if the pump is getting continuous power at the point of cut out.

If you don't know how to rig this up, you could try an alternative... jumping direct power to the FP (making it run at all times) and taking the car for another test run.

With what you've described, I think boost leaks, WGFV, altitude sensor, etc... are not within reason.  To have an "on / off" switch effect on the engine, you must be loosing fuel, loosing ignition, or dramatically overfueling... IMO.


-----Original Message-----
From: Manuel Sanchez <manuelsanchez at starpower.net>
To: s-car-list at audifans.com
Cc: James J. McCarthy <jmccarthy at oeb.harvard.edu>; QSHIPQ at aol.com
Sent: Fri, 21 Sep 2007 6:39 pm
Subject: [s-cars] Drastic Power Loss-So far No Joy

Still hunting for whatever is causing my drastic cut off of power  
ear peak boost. This happens with my MRC RS2 software in my ECU as  
ell as with a bone stock ECU. So with my RS2 ECU I hit the wall at  
bout 26-27 psi, when the Stock ECU is installed (with the stock  
njectors) I hit the wall at about 13-14 psi.
Many of you have suggested I'm experiencing an Over Boost situation  
nd have given me some avenues to pursue, here's what's been done today:
1. My RS2 WGFV
hecked with a multimeter, and it's within spec
2. Other used, Stock OEM N75 WGFV
hecked with multi-meter, within spec
nstalled in my car, test drive results in the drastic cut off in  
ower (nuts)
3. Inspect Wastegate Diaphram
o tears are apparent. Will test vacuum on this tomorrow hopefully.
4. Turbo Outlet hose and Wastegate hose (that small diameter crinkled  
nd ultra expensive bugger).
wapped these hoses, as well as this other stock N75 WGFV into my  
ar, same boat anchor results

ome people have suggested the altitude sensor, hopefully I can check  
hat soon.
What's puzzling, is that I think many of these electronic items would  
hrow a code if they were malfunctioning, no? Previously the only  
odes I had been receiving were :
00537 – Oxygen Sensor Control
aximum Control Level Exceeded
uel Tank Low resulting in fuel system pressure less than 3.3 bar (48  
si) [Note tank was ¾ full as indicated on fuel gauge]
gnition System Failure
O before 3 way catalytic converter less than 0.5% (Hmmm, what could  
his mean???)
uel Consumption high
ill Fuel Tank (tank had plenty of gas, and fuel gauge reads accurately)
00537 – Oxygen Sensor Control
inimum Control Limit Exceeded
ngine Intake Air Leak after Mass Air Flow Sensor-G-70
eak in Exhaust System in front of 3 way catalytic converter
eated Oxygen Sensor (HO2S)-G39-malfunctioning
uel System Pressure greater than 4 bar (58 psi) [This is  
nteresting, seems like I will throw this code all the time if I set  
he Fuel Pressure to 4 Bar/58 psi, which is what I believe I’ve been  
old is the Fuel Pressure for RS2’d cars. True?]
ich Exhaust
park Plug Fouling
O before 3 way catalytic converter greater than 3%
epair Leak
heck HO2S-G39
heck Fuel System Pressure
0561-Mixture Adjustment
daptation Limit (mul) exceeded
uel System Pressure too low
park Plugs, ignition coil, ignition coil power output stage  
educed Fuel Economy (no kidding)
ooty Exhaust (yeah, in spades)
ill Fuel Tank
epair Leakage
heck Fuel System
heck Fuel System Pressure
heck G70 (Mass Air Flow Sensor) [We cleaned the OEM MAF with MAF  
leaner, and we also installed a brand new RS2 MAF-we still had the  
rastic engine cut-off]

ately  we've been thinking that whatever the fault is, it's  
omething mechanical as opposed to electrical (that would throw a code).

ome people have suggested  a few things that we haven't had time to  
ry yet:
Altitude sensor
Check the wiring between the MAF and ECU with an ohmmeter
Throttle Position Sensor - the ECU allows boost only when the  
hrottle position sensor is above a certain value. So you could check  
he sensor
Light on the fuel pump to see if it's getting cut off when the Cut in  
ower occurs (I'm not exactly sure how to rig this up actually),
Hopefully I can check these soon.

ny other ideas are greatly appreciated.

5 UrS6 (still kickin my arse)
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