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FAQ part 7/10

Chapter 16.0: Fuel Injection Systems

Section 16.1:	My engine surges/stumbles when cold

	(by Rick Kjelsden:  [email protected])
The most common cause is vacuum leaks.  They allow extra (unmeasured)
air into the intake manifold, and mess up the mixture.  When the car warms
up the O2 sensor comes on line, so the Motronic can compensate.
Look for vacuum leaks in cracks in the air intake boot, or other air lines,
around the injector o-ring seals, through the valve cover gasket and
probably other places as well.
Find them by spraying carb cleaner at the suspected spot when the engine
in running (warm or cold).  A momentary change in the idle speed indicates
a leak.

==============================
Section 16.2:	Is it required to use fuel injector cleaners?

A:	(by Don Eilenberger: [email protected])

MOST better grades of gasoline do have cleaners in them now.. Mobil, Amoco,
Shell, Sunoco, in the premium grades probably do have enough to keep most
of the crap off your injectors.. except in the case of some older (read maybe
yours) injectors. There was a known problem with Bosch injectors called the
hot-soak problem, where residual fuel on the tip of the injector would bake
on becoming a carbon like deposit after a period of time. This caused BMW
lots of money, since they ended up fixing it under warranty. There was also
a problem with carbon buildup on the intake valves.. again, this cost BMW money.

So... BMW set it's own standards for fuel - especially the amount of cleaner
in the fuel. This became known as the "BMW test" (and apparently BMW NA
actually did take samples and test the fuel).
About 2-3 years ago, most gas companies started trying to pass this test,
and **most** did. Consumer's Reports published several articles on gasoline
and listed which ones passed the test. The ones mentioned above did.

IF you experience no bad-running problems EVER.. you probably don't need to
use injector cleaner (the only ones worth a damn are Techron and BG44). If
you do have bad-running problems (hard starting, rough idle, etc) - it will
not hurt to give the vehicle a dose of cleaner - provided you don't overdose
it without changing the oil (read the back of the bottle). It **may** clear
up minor injector problems - then again, the problem could be something else.
Cheap to try.

I personally, usually give my 535 a single dose of full strength Techron
the last tank before I do an oil change - and then only every other oil
change (so I'm doing it about every 6k miles). I look at it as cheap
insurance that I'm not clogging or crudding up the FI system. Probably doing
NO good whatsoever - but also doing no harm.

==============================
Section 16.3:	My transfer pump buzzes loudly

A:	(by Mike Daun: nicmad!daun%[email protected])
This is interesting.  I've been told by several people (including some BMW
mechanics) that they all buzz.  I've never believed this, sounds like
you've got a better mechanic than I do.  I notice that the buzzing is a lot
louder on hot sunny days (like when the fuel in the tank expands and builds
up some pressure?)

<<<<<	(by Mark Rubin: [email protected])

  > If you MAIN pump is buzzing, you probably have a dead transfer pump in
  > your gas tank ..

A "buzzing" noise *is* the symptom.  Two different mechanics have
told me the main, above-the-tank, high-pressure pump won't last long
without the transfer pump feeding it.
Guess I have some kind of rust/goo/contamination in the tank, and
it's clogging the pump or filter or something.

<<<<<	(by Ted Crum: [email protected])

The fuel pump buzz changes note as the idle speed varies because the battery
voltage is changing with speed.

==============================
Section 16.4: How do i check if my transfer pump is gone?

A:	(by Jim Conforti: [email protected])
Here's how I determined that ..

First .. main pump is making loud buzzing sound ..

Second .. Access the transfer pump, borrow stetoscope from Nurse Wife

Third .. bypass fuel pump relay and listen to transfer pump ..

Now you WILL hear what sounds like the xfr pump working, but it is really just
a column of sound from the main pump, up an hose of incompressible fluid (gas)

So ..

Fourth .. Listen to the xfr pump area while disconnecting and reconnecting the
          xfr pump connector (smaller 2 pin job) .. hmm .. NO CHANGE in sound
Which means ..
    DER PUMPEN IST TOD


	(by Rick Kjeldsen: [email protected])

Noise isn't always accurate.  I've seen a transfer pump which "works" (i.e.
runs) but doesn't pump any gas.  The only sure check is to pull the hose
from the transfer to the main pump, bypass the fuel pump relay to provide
power to the pumps (the pumps only run when the engine is RUNNING, not when
just the key is on) and see if the transfer pumps pumps gas (you may want to
remove the connectors to the main pump when you do this so it doesn't run dry).

==============================
Section 16.5: 	How do i change my transfer pump

A:	(by Jim Conforti: [email protected])

(Editor's note: this applies to an E30)

Simple job, 15 minutes max ..

Thanks to all the tips ;)

BTW, I used a handivac to cleanup all the dust on the top of the tank,
before opening anything ..

Here's what I did .. (just for posterity and others who may have to do this)

1) Remove lower rear seat cushion, and remove access cover .. clean up dust!

2) Disconnect 2 sets of wires, 1 for sensor, 1 for pump

3) Remove 2 orig. clamps (with diag. cutters)

4) Remove 4 nuts and washers from sensor ..

5) Slowly remove sensor to avoid gas mess ..

6) Remove 2 hoses from xfr. pump and rotate and remove pump

   Note: once you have "unlocked" the pump, you'll have to turn it around
         a bit to remove the pump from the gas tank ..

7) Reassembly is the reverse, using 2 new hose clamps and 2 new o rings ..
   1 is included with the pump, and the second fits on the sensor and costs
   3.00 (big deal) .. don't forget to pry out the old sensor o-ring which
   fits into a recess under the sensor bolt flange, around the sensor body
    tube .. use a paper clip ..

I detailed this for 1 main reason, note that the best way to make sure that
nothing falls into the tank, is to make sure that nothing is NEAR the tank
opening that CAN fall in (like nuts, hose clamps .. etc ..) :)

OH, AND BTW .. a bad transfer pump DOES affect idle quality .. once I replaced
the pump .. I restarted to check for leaks .. it took about 15 sec. for the
buzzing to stop as the system assumed proper pressure ..

Then on the test drive, my idle now stays ROCK steady and smooth ..

<<<<<	(by Harvey Chao: [email protected])

(Editor's Note: I believe this applies to a 5-series)

You will need:

1 screw type 1/2" hose clamp
1 screw type 3/4" hose clamp
(These are to replace the crimpons, which you just wheedle out
carefully with needle-nose pliers)

That's it!  Of course, to be really safe, you should buy the gasket
that seals the transfer pump to the gas tank.  The sending unit
is in the center of the transfer pump mechanism.  The sending
unit is non-servicable.  It is a silver canister, about a foot long,
with electrical connections on top and a small nut with ground
strap on the bottom.  There are a couple of small (2 to 3mm)
holes down the side of the pump.  You'll get gasoline all over
yourself if you aren't careful when you remove it.  The new
sending unit should have the o-ring, but check to make sure
it does.  I tried to take my sending unit apart, but all I did was
screw it up worse (silly me - I thought it was the transfer
pump at first!)

Steps to get the unit out:

1) get access to it first (remove trim piece in back of trunk)
2) lift up floor of trunk
3) Unscrew the cover - it's a disk about 8" in diameter
4) You need a 7mm socket wrench.  Pretty small, so make
sure you have one.  It's the same size that the distributor
cap uses on an '83 528e.
5) Take the hoses off FIRST - makes life a lot easier
6) There are two nuts for the sending unit - you have to
take the sending unit out to get the transfer pump out,
unless you like to spend about 5 minutes trying to angle
the whole assembly out
7) Unscrew the 8 or 9 bolts for the transfer pump slowly,
going round and round (I did that because I didn't have
a new gasket and didn't want to mess it up)

Truly, it is *very* easy to do.

==============================
Section 16.6:	An aftermarket pump for a bimmer?

A:	(by Sam Chien-shin Lin: [email protected]: edited)

I paid $29.48 for a BWD P1 pump and $1.99 for a pack of hose clamps and
headed home.
BTW, the dealer doesn't sell the strainers separately - YOU HAVE TO
BUY THE WHOLE PUMP!!!  Pep Boys sells a BWD F4 strainer for $4.12 which
fits nicely on the VDO and the BWD P1 pumps.  It is a different design
from the BMW part, but the fitting is the same, and it appears to have
more surface area than the BMW part, so it should flow better.
Anyway, it's 70 micron polyester mesh.
The hardest part of the kludge was popping the rivets that held the
positive wire and the brass negative strap onto the old VDO pump.
Looking carefully at the VDO unit, I noticed that the mounting bracket
had an outline around it, which would leave just enough extra plastic
to clamp on my hose clamps.  I got out my hacksaw to cut along the
outline and used two hose clamps to clamp the bracket onto the Vega
pump.  After some fiddling, I was able to adjust the positioning so
that the wires would reach and the short rubber connecting hose would
fit.  Using the screws supplied w/ the pump, I connected up the
terminals and Voila!  Done!  When I tried to install it, I ran across
an unpleasant surprise...the hole in the fuel tank is such a tight fit
that the hose clamp screws wouldn't clear; I couldn't get it into the
tank no matter how I tried.  Back to the drawing board...
I had to throw away the mount I cut out of the old pump, was too thick
to fit into the fuel tank.  Finally, I got a short length of fuel line
hose and slipped it over the fuel return tube (for shock absorption and
traction) - the fuel return tube is what the mount/negative terminal
is welded to, and then secured the pump to the hose-covered return tube
with two large nylon wire ties (the zip-on type).  It might not sound
secure, but I pulled on it hard, and it was firmly secured.  This
time, it fit into the tank w/ room to spare.
BTW, the later models do away w/ the transfer/main pump setup, and
have only one pump in the gas tank.

==============================
Section 16.7:	How to cure fluctuating idle problems

A:	(by Jim Conforti: [email protected])

First, make sure your ICV (The VALVE, on the intake manifold) is of the
metal type .. some of them were plastic and there WAS a recall

Second, remove and clean the carbon out of the ICV valve ..

Third, any time you replace the ICU or ICV (preferably BOTH at once!)
you must adjust the current via the screw on the side of the metal ICV
(If you have plastic valve, the screw is inside!)

The current MUST be set to the proper current for your year/model
See the Bentley or factory manuals ...

The Throttle body must be properly set via feeler gauges ...
When the ICU/ICV goes south many people try to set idle with the
throttle screws ... BAD, BAD, VERY BAD, NO GOOD!

Now, If the ICV is metal and clean, the current is adjusted to spec, and
the throttle body is too .. disconnect your O2 sensor .. if the fluctuation
stops, your O2 sensor is/was going bad, replace it!

Lastly if NONE of the above cures the problem .. a failing engine temp
switch (if it signals cold [< 45C] engine mistakenly) will cause the ICU
to hold idle at 950 RPM ... this sensor is on the engine, usually part of the
collant temp sensor, a switch type deal, see the Bentley for more info
Also a faulty air temp switch or A/C on input will bring idle to 850 rpm

(Editor's note: A faulty transfer pump can also affect idle quality)

==============================
Section 16.8:	All about Idling you wanted to know (TechFAQ)

A:	(by Sam Chien-shin Lin: [email protected])

Sam has compiled an excellent FAQ on idle problems. Its too big to be
incorporated here, so please contact him.

==============================
Section 16.9:	Oxygen Sensor info

A:	(by Don Eilenberger:[email protected])

1. Yes - you could use a generic O2 sensor - if it was a 3 wire heated
one (there are Lucas [the inventor of darkness] 3 wires being sold
as a universal heated replacement... they will FIT the BMW.. how well
they work?? Your guess].

2. You would be better off going to your friendly Ford dealer and asking
for DV505 - this is a 3 wire for a Mustang V8.. just happens to be made
by Bosch (hmmmm... who makes the one for BMW).. just happens to look
exactly the same as the BMW one.. except for the wires. Some splicing
required (white to white.. black to black). Cost? Somewhere around $40..
vs the $130-180 for the genuine BMW one.  Works just fine in my 535i..

<<<<	(by John Dempsey: [email protected])
> How can I tell if the O2 sensor is bad in my '84 325e?  I followed the
> instructions in the Bentley manual by warming up the car and unpluging the O2
> sensor to take a reading.  The reading started at .408 and continued to fall
> toward 0.  When I removed the oil cap the meter went to 0 as described in
> the manual.  Shouldn't the first reading fluctuate within a given range and
> not continue to fall toward 0?

What are you using to get those readings?  The output should fluctuate, but
you'll never see it with a DVOM- too much averaging.

And what is the situation by which you tested the sensor?  Both when you first
checked it, and removed the oil cap.  We're dealing with a single wire O2
sensor, right?  Did you check it at all with the car at high RPM's?  Like
around 2000 RPM.  Or did you only check it with the car at idle?  And why
are you checking the O2 sensor anyway?  Got some problems with the car, and
its drivability?

If you can answer the above (and maybe do some further testing, as mentioned
above), I could better interpret the results.

First off, .408 is a bit on the low side- a bit lean.  And as far as going to
zero, I'd say that whatever the ground was that you used for the meter, had
too much resistance.  In other words, it was not a good ground.  All the O2
sensors I've seen at least put out some type of voltage, even if they were
defective.  Ussually the voltage is low, but not zero.

BTW, how long did it take to go to zero?


- - ---------------------------------------------------------------------------
Chapter 17.0: Tires

? Section 17.1:	How to choose the right tire for your car

==============================
+ Section 17.2:	Tire Survey (Summary)

A:	(by Aaron Lung: uunet!uu2.psi.com!megatest!plethorax!alung)

<This has been converted to a mini-FAQ. Please contact Aaron Lung for this.
In future, this will be at the "balltown" site. Check the list for further
details.>


==============================
Section 17.3:	Winter Driving and BMWs (FWD vs RWD) (Summary)

A:	(by Walter G Barie: uunet!pitt.edu!wgbst4+ : edited)

Yes, you can get going easier with FWD but I find that braking and
going down hills in the snow is much more controllable in a RWD car.  I
also find RWD much MUCH easier to control overall, it seems that once you
lose it in a FWD car in the snow or ice, the slide/spin seems much harder to
control.  I believe the controlabilty that RWD provides is more important than
any slight ulitmate traction advantage that FWD has.

<<<<<	(by Steven Bernstein: [email protected]: edited)

Rear wheel drive will forever be different from front wheel drive, but
they're targeted to different audiences.  The physics is different.  Front
wheel drive is more forgiving, rear wheel drive is more fun.  Front wheel
drive cars, *including* Saabs, IMHO, are more difficult to work on than
rear wheel drive cars because so much more stuff must be put in the engine
compartment. And fundamentally, I think a person has to be a better driver
to handle rear-wheel drive, particularly in dangerous situations.
Obviously, for most of us here, we understand that and are willing to make
that trade-off.

<<<<<	(by Richard Welty: [email protected]: edited)

I decided to pretend that winter driving was a low-speed performance
event, and started to apply some basic performance driving principles:
1) lots of straight line braking approaching corners and 2) smooth even
throttle application throughout the corner, leading to an implementation
of 3) slow in, fast out
you know something?  it works really, really well.  what the snow means
is that you are suddenly in a performance driving domain, whether you
realized it or not, and whether you normally drive that way or not.
get used to it.

<<<<<	(by Gene Kern: [email protected]: edited)

My winter tire recommendations are:  (based on personal experience)
1.  narrow studded tires at all four corners. (heavy snow and ice)
2.  narrow snow tires at all four corners with studs at rear.
3.  narrow snow tires at all four corners.  (mild snow/light ice)
4.  narrow all weather tires at all four corners (light snow areas)
5.  cheap winter ride with snow tires.

<<<<<	(by Rolf Jungbark LG/TF: [email protected]: edited)

Anyway, the conclusion is that if a RWD car starts to slide in a turn,
it most often does this at the rear end. The rear end will end up in
the wrong lane and the car will be hit in the side. A FWD car will
most often start to slide in the front ending up in a head on collision
that will use the front deformation zone that gives better protection.
Another part in the conclusion is also that FWD cars are generally
more stable in the snow and cause fewer accidents (remember the
statistics above!).

My own opinions on the subject is that it is all a case of vehicle
dynamics. Let's make an experiment. Take out a pencil, put it on
the table. Hold the tip of it gently between your thumb and
index finger and pull it in a straight line across the table. No
problem eh? The pencil moved in a straight line right? Now, use
your index finger to push the pencil at the tip in a straight line.
That wasn't a straight line, was it?
So, a FWD car will tend to pull itself in a straight line and a
RWD car will try to turn around. This also makes a RWD able to
steer faster than a FWD car, generally. You can test this ability
on your bimmer by applying throttle in a turn and note that it
will steer more. But don't ditch it!
By the way, when you "motor brake" (I don't know the proper english
word, but what i mean is when you remove your foot from the throttle)
in a FWD car it will cause a force to be applied at the front which
causes an instability that can create a slide (I once felt this
instability in my brothers old saab 99 on a gravel road, i accelerated
hard and then i dropped the pedal which caused the car to feel
instable. Applying a bit of throttle cured this).

But there are other factors that contribute to the behaviour of a car.
For example weight distribution. If you throw a hammer (don't do
this, you might hurt someone!) it will travel through the air
with the heavy end first. This is because at the heavy end
drag/weight is less. The same applies to a car, if you lift it
by helicopter and drop it the heavy end will travel first.
Most FWD cars are front heavy, this makes them more stable in
a straight line. This is another cause why a bimmer can outsteer
most FWD car.

Another factor that contributes to the behaviour is the forces
applied to the car by the wheels. On an icy road this is very
much dependent on the friction caused by the tyres!
A wide tyre will ride on the snow, a smaller (correct term?) will
dig through the snow. Wide high-speed rated performance tyres have
rubber that gets stiff when cold, it's like driving on bakelite
tyres! As Richard mentioned placing different tyres on the
axles creates imbalances (He said his saab was worst with studs
in front and bald summer tyres in the rear).
You should always have the best tyres on the rear axle!
Most people think that it should be the other
way around, but that is NOT correct. The cause for having them
on the rear is that this creates stability. In fact they act
much like the feathers at the end of an arrow or a dart. You
can test this by taking a small toy car (if you don't have one
buy one at the bmw dealer, then you can have an 850CSi... :)
and put tape on the wheels. Apply the tape with the non-sticky
surface out... Then let the car down a sloping surface (you can
set your table at an angle). Check the difference between having
tape on the front vs the rear wheels! By the way, guess why
the front breaks of a car are to lock before the rear ones...

Some rules:
- - - Do not apply power in a turn in winter, this
	will causes forces that can create a slide.
- - - Do not break in a turn in winter either...
- - - Don't use wide high-speed rated low profile performance tyres.
- - - Have the best tyres on the rear axle.

<<<<<	(by Roy Richard: [email protected]: edited)

Here are what I consider the primary variables in this fine
winter (hopefully non-contact) sport:
1.Driver and Driving Style- Practice-Practice-Practice- Richard
Welty is correct in emphasizing driving skill as the most
important factor in winter driving. Furthermore his observation
that "winter driving was a low-speed performance event, and
started to apply some basic performance driving principles" is
exactly right and one of the reasons I enjoy It so much. You can
get into a beautifully controlled 4 wheel drift at speeds below
30 mph! Most importantly snow driving takes finesse, no sudden
move, very little braking, smooth controlled acceleration. But
practice is the key. Whenever I get the chance, and especially
with a new car and at the beginning of the winter, I find a nice
ice and snow covered parking lot sans parked cars and practice
turns, braking, recovery maneuvers and try to find the rear end
adhesion limit. It is critical not to have to learn how to
control you car when the boob in front of you is pulling 360's
at 50 mph on I89.( Note this often tends to be 4 WDrivers who
haven't figured out that we all have 4 wheel brakes and that the
shit handling of a Bronco doesn't improve with snow).  Just a
few tip that many of you already know; a. If you are stuck
spinning a wheel gently apply the emergency brake to get
traction to the spinning wheel (this doesn't work too well on
most FWD vehicles but some Saabs do have front wheel E-brakes)
b. Try to stay off the peak of the torque curve which usually
means shifting a little sooner and letting the engine lug a
little more than usual. Some times you may need to "spend" a
little clutch, keeping the engine RPM up while feathering the
clutch. This may seem brutal to some but I do it when required
and typically get over 100 Kmiles out of a clutch so its not
that bad. c. Braking is the maneuver of last resort. Use engine
braking whenever possible, don't pull radical down shifts and
practice those nice smooth heal and toe's. d. Don't get caught
too fast in the corner, gently straight brake before the turn.
If you do get caught too fast in the turn gentle acceleration in
probably your best bet. d. Skid recovery really is a matter of
reverse steering and developing a feel for your vehicle, you
have to practice this in a safe place.

        2.Tires; are critical to good traction and handling. Use snow
tires all around to maintain good handling balance. Studs all
around are great for extrema conditions but I find the vibration
at 75 mph on dry pavement just too much. Studs in the rear
really help on ice but don't do much in snow. Narrow tires are
also better they don't tend to float as easily and don't snow
plow.

        3. ABS: if you don't know why don't drive in the snow

        4. Transmission; One work STANDARD. I know some people love
there automatics in the snow and they are easier to rock if your
stuck but overall you just don't have the control for down
shifting or control of power by slipping the clutch.

        5.FWD v/s RWD: well here's the BIG ONE and (IMNSHO) the answer
is non of the above. There is no clear winner in FWD v/s RWD the
particular design car is far more important than FWD or RWD and
even if all else is equal they both have their positive and
negative points. Clearly the best of both worlds, AWD if
properly designed will win hands down. But even AWD won't
improve the handling of a DOG. The question of FWD and RWD in
snow is really one of three distinct areas: Traction, Handling
and Emergency Maneuvers. I general the FWD is better for
traction and getting out of the snow bank. They tend to have
more weight on the driving wheels and when you steer they pull
in that direction. Handling wet, dry or snow goes to the good
RWD. I think the reason that a lot of drivers don't like the
handling of the RWD in the snow is that you do have to drive
like your in a low speed performance event and utilize
controlled power slides. However; my 7 series is very well
mannered and predictable and FUN to drive on a slick surface.
The front wheel drive vehicles I've owned and driven tend to
give you better low speed steering control but once loose are a
real hand full with no means of controlled recovery. The really
key features missing in the FWD is the ability to engine brake,
well you can but!, and the ability to smoothly break the rear
end loose ( yes some people do this on purpose). Where I found FWD
particularly scary was on really slick down hill braking, you loose
all sense of having any form of control. For emergency situations ABS
is more important than FWD or RWD. Beyond that RWD will give you
better handling , if you take the time to learn how to drive,
and therefore a better overall chance of keeping control. FWD
tends to give the less skilled driver a false sense of security.
They do tend to feel more "normal" on a slick surface until
things start to come loose e.g. a emergency situation and then
they just fall apart.