Lost boost

robert weinberg centaurus3200 at yahoo.com
Fri Mar 27 08:57:48 PDT 2009

wow, sounds like you've checked most everything. 

my car had the same issue. 034 motorsport was about ready to drive it off a cliff ;-)

turned out to be corroded ecu ground wires. but sounds like you checked them.


--- On Fri, 3/27/09, Jani Lundqvist <jl_76 at hotmail.com> wrote:
From: Jani Lundqvist <jl_76 at hotmail.com>
Subject: Lost boost
To: 200q20v at audifans.com
Date: Friday, March 27, 2009, 1:34 AM

Hi'ya all

I've been trying to find the missing boost. It started intermittently, and
no it's seems permanent 1.2 bar on the dash dial and that's with WOT on
fift gear. I've checked the list on SJM site:

Check for any stored ECU fault codes, are the knock sensors working ok?
"pulled codes yesterday, only code 2231, ISV is working, could faulty MAF
do this"
Read the Measurement block values using the VAG-COM, look for anything out 
of the range "haven't tried that yet"
Check basic engine timing, flywheel, camshaft and distributor rotor position
"check"Check Throttle Cable Adjustment "check"Check Air
Filter, is it really clogged up? "just put in new one"
Check/Replace the Turbo Bypass Valve, check small vacuum/boost hose to this 
valve "checked, should be OK"
Check Idle Stabilizer Hoses, and other small vacuum/boost hoses "checked
and replaced"
Check basic fuel pressure and correct operation of the rising rate fuel 
pressure action by applying vacuum or boost to the vacuum/boost hose connection
"checked and replaced"
Check fuel pressure regulator for leaking into the vacuum/boost hose fitting 
(rich running) 
"changed the pressure regulator, was leaking"Check ECU Connector
Terminals for corrosion, remove connector and use 
contact cleaner "cleaned"Replace small vacuum hose from Bypass valve
to Intake Manifold (3B engine) "done"Check the Operation of the
Multi-Function Temp Sensor (1991 200Tq 20V Only) "replaced, and have tried
to disconnect it, no avail"
Temporarily disconnect Multi-Function Temp Sensor 4 pin connector and 
recheck boost output (1991 200Tq 20V Only) "tried"Remove and inspect
the Intercooler exit hose (Ribbed Hose) and the lower 
turbo exit pressure hose for leaks. "doesn't leak"
Check the rubber hose between the intake pipe and the throttle body.
"checked and cleaned"
Check Vacuum hoses and their connections at the back of the intake manifold
"checked and replaced"
Check/Replace the coolant thermostat, is the engine running too cold? or too 
hot? "this is still on to-do list, mind you temp is OK"
Check Engine Coolant Temperature Sensor Resistance and connector wiring
"haven't tested, gauges are working ok though"
Check the operation of the Waste Gate Solenoid using the ECU Output Test
"still to be done"
Check Waste Gate Solenoid hoses "checked out OK"
Check Air Temp sensor resistance at the ECU, and Repair the Air Temp Sensor 
wiring connections if needed. "these were OK as well"
Check Throttle Position Switch/Potentiometer for intermittent operation
"checked this, at least my multimeter didn't find anything wrong,
resoldered the connections as well"
Check Altitude Sensor Voltage Output and wiring between sensor and ECU
"still to be done"
Plug or pinch off hose to lower waste gate and check for maximum boost and 
overboost cutout "still to be done"
Check Waste Gate for sticking open, defective spring? "need to get my
hands on a vacuum pump"
Check the Exhaust System Back pressure, possible exhaust restriction
"exhaust' fine, checked it yesterday"
Inspect the Turbo inlet vanes and end play, has the turbo compressor nut 
left the building? or the turbo seized up, broken in half, or otherwise gone 
south? "Turbo checked out, no end play, no extra sound"

My comments in red, other than that, the car runs fine, just got through the
Finnish MOT inspection without any faults. So once I find the missing boost,
I'm all set for the coming summer, seems quite long way away, -20 C this


"It's not that I'm so smart, it's just that I stay with
problems longer." - Albert Einstein 

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