frequency valve, 200tq '89 MC2

[Stott Hare]

Okay... time for me to chime in here.  Patient is also an 89 200tq with the
MC2 motor, 275k.  Car was running okay, meaning it ran smooth, started a
little hard when cold, but never got more than 1.2bar indicated and had
lousy fuel mileage.  But its PO hadn't attended to it properly for a while,
so I thought I'd be a nice guy and start refreshing my new ride.  I gave it
a once over and identified some damaged vacuum lines, bent braided fuel
lines, and a faulty control pressure regulator.

What I fixed....
I replaced with new parts: fuel filter, air filter, plugs (W7DTC), cap,
rotor, throttle switch, injectors, injector seats, injector seat seals, oil
filler cap gasket.
I replaced with used parts: control pressure regulator (with one providing
correct control pressures), crank case vent hose to T-junction on valve
cover, braided fuel lines
I repaired with generic parts: hose between waste gate and WG freq valve,
hose between intake and injector shrouds (transferred restrictor), soldered
connections at intake air temp sensor, dip stick oring, spliced hose coming
off 90* elbow at turbo intake.

What I checked...
I have cleaned the fuel bowl, tightened all valve cover 10mm nuts, tightened
all hose clamps in intake tract and misc vacuum and breather hoses.
I have checked for cracks/leaks: intake waffle boot, 90* elbow at turbo
intake, Michelin man hose, crank case breather hoses and T between block and
waffle boot.

What I tested...
I have tested control pressures, system pressure, flow rates and check
valve.  All test out in spec.
I have flogged the car and dumped codes, getting only 4444.
I have ran the output tests and found that Bentley has the codes out of
order (D2-150-2, 4442 will prove out before 4443).  However, I also find
that 4343 (Carbon canister shut off valve) does not prove out during this
process.

Where I ended up...
And the end result?  The car starts easier, will occasionally reach 1.4
indicated.  However, the gas mileage still sucks, the idle is lopey, the car
stumbles occasionally during acceleration, and is often unhappy at a steady
throttle state.  It almost seems as if their is an ignition problem.  The
idle is so lopey, the exhaust sounds like it has holes in it.  But I've
checked the exhaust over and it and it's cat/downpipe junctions are tight.

What I plan to do next...
My immediate plans are to perform compression and leak down tests, check and
reset idle and mixture as needed, track down a working carbon canister shut
off valve.  I may even get new wires, an O2 sensor, and a fresh rubber VC
gasket.

And my questions...
Phil, you mention a sloshing noise.  The MC2 has an external fuel pressure
regulator.  One odd noise I noticed while running the output tests, was that
if one listened closely to the fuel distributor, there was a pronounced
hiss/slosh noise like there was air mixed in with the fuel that was flowing
through.  Does this ring any bells?  Should I be digging into the fuel tank
to check the pump?

Also, I replaced the vacuum hose to the injector air shrouds with generic
hose.  However, I did transfer the restrictor and it seemed like a tight
fit.  What problems might I have caused if the fit wasn't tight enough, or
if the restrictor is installed in reverse?

I'm looking for any suggestions at this point.  I think I have checked and
ruled out all the usual vacuum leak suspects, but I'd be happy for someone
to prove me wrong if it improves my cars poor running condition.

Thanks!
-S

Stott Hare
85 Callaway 4ktq     89 200q     89 100q


-----Original Message-----
On Behalf Of isham-research.freeserve.co.uk at pop.pol.net.uk
Subject: Re: frequency valve, 200tq '89 MC2

> what is cavitation?

--snip--
Another way to check for this phenomenon is to use a stethoscope on
the system pressure regulator.  If you hear a steady sloshing of fuel
despite the pump noise being intermittent, this is it.
--snip--