Mystery3B problem (long)

[PeterBergin at aol.com]

When mine failed, I read some stuff on SJM's site concerning problems in  
the connector at the MAF.  They also give you some information to test the  
pins for voltage, ground and resistance.  I never did that, but the  
information on the site might help.
 
Pete, 91 Avant
 
 
In a message dated 12/20/2010 11:54:52 A.M. Central Standard Time,  
alancordeiro at comcast.net writes:

I had  very similar symptoms...it was a bad MAF.....but since you swapped 
that,  let's assume that is good.

Is there any way you can check the wiring  integrity from MAP to ECU? any 
special grounds used exclusively by the MAF  circuit?

Finally...any head work is suspicious...the timing on the  belt, or even 
worse, if someone replaced the chain between the two  camshafts wrong...may 
be the cause of the problem. Its easy enough (in  theory) to check 
timing...line up the mark on the flywheel, the crank  pulley, and the 
camshaft mark (spotting the flywheel mark is the  challenge).

Sorry, out of more ideas...good  luck,

Alan

----- Original Message ----- 
From: "Ben Swann"  <benswann at verizon.net>
To: "'200q20V mailing list'"  <200q20v at audifans.com>
Cc: "'Ben Swann'"  <benswann at verizon.net>
Sent: Monday, December 20, 2010 10:32  AM
Subject: Mystery3B problem (long)


>
> Brought to you  by Ben's Brain Benders and Knuckle Busters
>
> Here we have  another diagnosis and trouble-shooting problem from hell..
>
> I'm  trying to see what I may have missed so far prior to delving into 
the 
>  engine itself.
>
> The car is a '91 200 20V quattro sedan.   Engine has 198k miles on the 
> clock.  The car
> was brought  to me in hopes that a brief look and some parts swapping 
might 
>  resolve a
> problem that has so far stumped the owner and apparently  prior mechanics.
>
> The engine starts but won't rev., runs rough,  and has no power - enough 
to 
> throttle baby
> it around, but  basically barely gets out of its own way.  The boost 
guage 
> never  shows
> below .7 on stock ECU and will generally idle at .8 or .9.   I hooked up 
a 
> guage and the
> engine is not pulling much  vacuum, perhaps around -8 PSI at idle.
>
> ***Here are some things  that were checked prior to me looking at the car 
- 
> many of  which
> I've confirmed.  *** My comments *** added to owners  original comments.
>
> [Owner comment - The wastegate diaphragm is  good.
>
> Owner pressure tested the system to about 25psi and it  was holding. Only 
> hissing came
> from around the dipstick,  which now has a new o-ring.
>
> Owner changed the ECU with a known  working unit that hasn't been chipped 
> and it didn't
> make a  difference.
>
> Owner replaced the O2 sensor with a brand new one  with the correct part 
> number. Again,
> no  difference.
>
> Owner claims timing is correct, there are all new  belts, pulley, 
> thermostat, water pump,
> valve cover gasket,  crankshaft and camshaft gaskets, valve job, head 
> gasket etc.  It's
> all fresh.  *** This is the part I am not sure about - see  details below 
> ***
>
> Owner replaced the distributor  rotor with a new one with the correct 
> narrow tip. The
> gear is  a metal one so no cracked plastic issues there.
>
> Owner   kept getting a code for the RPM sensor so replaced that.  No 
change  
> and still
> shows a code. **code has cleared**
>
>  Owner thinks the multi temperature sensor must be bad (or the wiring) 
>  because the
> coolant temp gauge works on and off. I haven't had a  chance to replace 
it.
> ***I explained that MTFS does not directly  effect the engine operating, 
> but is for the
> temp guage and  coolant reservoir and after-run system***
> *** There was a CTS code  that probably was what he was referring to - 
more 
> on that  below
> ***
>
> Owner comment - I don't remember all the  exact codes. There were a lot. 
I 
> recall RPM
> sensor, running  rich, overboosting and there were others. I'd check them 
>  first.
>
> Owner comment - The hose going to the bypass valve is  new also and tried 
> another known
> good valve. None of it made  a difference.
>
> Owner comment - I tried replacing the wastegate  frequency valve with the 
> one out of my
> '02 S4. It's the same  but part numbers are different. For whatever it's 
> worth, there  was
> no improvement. Could it still be bad? I don't know.  ***  This all looks 
> good to me ***
>
> I did the output test  and everything clicked properly. The only thing I 
> couldn't get  a
> signal from was the carbon canister solenoid. It's behind the head  on a 
> hose. I replaced
> the too and no difference. I checked  the power going to the wires and if 
I 
> recall
> correctly there  was none. *** Here is where I found some problems - 
> explained below  ***
>
> Owner comment - I tested the throttle position sensor and  the harness. 
It 
> all checked
> out. I even took it apart to  check for any broken traces. It's all good.
>
> Owner comment -  I  tested the altitude sensor. I think that's what it's 
> called.  The one
> that's on the intake manifold, right after the throttle body.  That one 
> checked out too.
>
> Owner comment - I was also  getting a code for the sensor that's behind 
the 
> driver side
>  kick panel. I think it was another sort of altitude sensor. I'm mixing 
the  
> two I know.
> My memory is failing me right now. Anyways, I  replaced that too with no 
> signs of
> improvement. *** I  clarified that the IAT is on top of the manifold and 
> the  altitude
> sensor is inside the car -  I followed up with testing  and substituting 
> known good
> sensor, but no change  ***
>
> Owner comment - The MAF I have not replaced so I have no  idea if it's 
good 
> or not. I
> think I checked the connector  though and it was good. It seems like 
> someone might have
>  changed the MAF with a used unit. There's a number written on it like 
you  
> would find in
> a junk yard. So maybe someone tried replacing  it, but who knows if it's 
> good.  *** I
> tried  good  MAF(s) - no change (even worse running) ??? ***
>
> Owner  comment  - The Michelin Man hose is good and I also checked the 
>  turbo. There is
> very minimal play in the shaft. Very normal. No sign  of the blades ever 
> hitting the
> housing.
>
> Owner  comment  - I haven't checked the fuel pump, fuel pressure 
regulator  
> or replaced
> the filter. I don't know what condition they are  in. The hose going to 
the 
> FPR is good
> and hooked up. *** Fuel  pressure test may be in order ***
>
> Owner comment - My S4 was  running well but I did a tune-up on it so the 
> spark plugs I
>  pulled out of it I put in the 200. I wanted to see if anything changes 
but  
> there was no
> difference. The wires and rotor I haven't  replaced so I don't if they 
pose 
> an issue.
>
> Owner  comment - That's all I can think of right now. So basically what 
>  happens is that
> the car cannot be revved up past around 4200rmps. This  doesn't matter if 
> it's in neutral
> or under load. When the car  is under load you can only give it gas very 
> gradually (not
>  the case in neutral, revs just fine up to a point), anything sudden will 
 
> cause it to
> buck severely.
>
> Owner comment - If  you do rev the car to that limit (4.2K), and do it 
for 
> a few  seconds,
> it'll start pouring out black smoke and you can hear it  misfiring VERY 
> loudly, like
> series of explosions. During one  of these episodes the boost gauge will 
> spike all the
> way up  to 1.9 bar(in neutral) and you can hear the relay inside the ECU 
>  clicking
> constantly. After you let off the gas the car will start  running rough 
and 
> the wastegate
> frequency valve clicks away  frantically.  *** this is strange 
explanation 
> of the  problem
> that I have not confirmed or witnessed - why would the engine  barely 
make 
> vacuum, yet
> overboost like  that?***]
>
> Presented with this list and discussion about the  car, I attempted to 
> trouble-shoot and
> isolate the  problem.  Here are excepts from my notes:
> - Obeserve problem as  MAP output to display - not correct?
> .Not pulling sufficient  vaccum,
> .Reads 1 Bar when engine not running (OK)
> .7 - .9 Bar  at idle - should be around .3?
> .engine revved/load change -> .6-.9  should be .3-.8?
> **Suspect vacuum leak in MAP sensor (vacuum)  circuit
>
> Hooked up VAG-COM: There were several codes at first:  (abbreviated 
> descriptions)
> 519 G71 Intake Manifold Pressure  Sensor - No Signal
> 522 G62 Coolant Temp Sensor - Short to  Ground
> 516 F60 Throttle Position Sensor (Switch) TPS idle - Open or  Short to B+
> 528 F96 Barometer/Altitude
> 513 G28 Speed Sensor -  OK, car not running
> 1262 N75 (Wastgate Frequency Valve) Open or short  to ground
> 553 G70 MAF low signal/intermittant
>
> -  Charged Battery
> -Tee'd in Mity-Vac and Boost Guage and found some  apparantly porous 
line. 
> Replaced 2
> line sections and tested.  Vacuum held at 25PSI for over 2 min - from 
> manifold to ECU
>  connection.
> -Restest - still has problem, and no apparent  change.
> -Pulled Codes - same as before.  Cleared Codes ->  Persistant or new 
codes 
> appearing now
> are:
> G62 CTS,  N71 Idle Stabilizer Valve, F96 Alttude sensor.
> Cleared codes again -  same appear.
>
> Proceeded to test CTS, wiring and after much wire  chasing and confusion 
> found what was
> sure to be the  problem:  There were 3 sensor connectors(CTS, EVAP, 
Heater 
>  valve) located
> near or in back of the head.  Someone had  connected the CTS to the Evap, 
> the EVAP to the
> heater and the  Heater valve to the CTS.  So I moved the three sensors 
> being out  of place
> to the correct locations.  Ready to call owner and  proclaim I found the 
> problem(s).
> Start car - runs as crappy  as ever.  (expletives deleted) - note CTS 
> sensor tested  in
> spec.
>
> Pulled codes/cleared codes/pulled  codes:  Get 528 Barometric/Altitude - 
> Open or short to
>  B+
> Tested wiring (OK) swapped in known good Barometric sensor.   Code 
cleared. 
> Car still
> runs same.
>
> Swapped  out MAF (using AAN and 3B MAFs) - no change or worse.  Checked 
>  wires under
> connector - looks OK.
>
> Note: Recall from  prior similar engines running like this were due to 
bad 
> MAF or  Bad
> Coil.
>
> Swapped Ignition coil - no  change.
>
> At this point I have far exceeded the estimated time  to repair this 
> problem.  I
> discussed possible problems  with the owner:
> All codes now cleared and fairly well believe wiring,  ECU, sensors to be 
> ruled out, even
> though there were several  latent problems fixed.  The problem now 
appears 
> to be more  of
> a physical problem with the engine.
>
> Some sort of  air intake or induction problem?  Possibly a fuel delivery 
>  problem.
> Suggested blocked cats - that has already been ruled out  accoring to 
> owner - exhaust was
> separated from DP and problem  existed.
>
> Based on the fact that the head was pulled and  decked/rebuilt and other 
> engine work
> apparantly done, I  enquired and found problem existed prior to the head 
> work.   ?
> Possible mis-alignment of exhaust w/resp to intake cam  ?
>
> What (else) could be causing this problem.  Ideas?
>
> Ben
>
>
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