Mystery3B problem (long)

[Ben Swann]

My main suspicion at this point is that the two cam sprockets are mis-aligned and the
head is not breathing properly.  Owner says that should not be a problem because the
head would have been re-assembled properly, but can not confirm the work.  He insists
the main belt is correct w/respect to the crank.  His reasoning the sprocket theory is
not valid is that the problem occurred before the head was rebuilt. I have the gut
feeling that whoever put the head back together used the 16v mark(s) on one of the
sprocket instead of the 20V mark and just copied the mistake that had been made
previously.  If I recall there are different marks for different heads, but the same
sprocket is used.  I have seen enough other things that were not correct, namely the
sensor connectors installed on the wrong devices, that I won't trust that whoever
installed the head, did it by the book as they did not bother to look at wiring diagram
to verify sensor wires/colors were correct.  Ironically this is a case where Audi did
not use idiot-proof connectors to ensure that the three sensors in same proximity could
not be hooked up improperly.

I can of course verify all this speculation, but will not touch the car again until
assured whatever service or diagnostics I'm doing is not going to be for free.  I
already went beyond what was expected, found and resolved several problems using up an
additional day of "free" time cause I'm a "nice" guy.  Right now I'm just looking for
options to present to the owner with greatest probablilty of success for amount of time
spent.

Does the mis-aligned cam sprockets sound like it is the most likely culprit at this
point based on all the other things I did/verified? What do you think Scott J?

Ben 

-----Original Message-----
From: alan cordeiro [mailto:alancordeiro at comcast.net] 
Sent: Monday, December 20, 2010 12:55 PM
To: Ben Swann; '200q20V mailing list'
Cc: 'Ben Swann'
Subject: Re: Mystery3B problem (long)

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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