Car starts and idles really low, sometimes stalls. When warm it idles at just under 1000 as normal.

What engine is in your car?

If this all happened after you replaced the battery, it could be
that the ECM lost its "Learned Throttle Adaptation".

Over time, the throttle bore in the engine gets dirty and the ECM
has to move the throttle more open, to maintain the specified rpm, because
the dirt is restricting air flow.

This re-learn (after a battery disconnect) can take a few minutes
or a few days before things are back to normal.

The best thing to do is to clean the throttle bore and then to use
a scan tool such as VCDS to perform a Throttle Body Adaptation / Alignment.

Such as I am doing here on a 1.8T VW engine:

http://www.youtube.com/watch?v=OAfeBLENkfA

If that did not solve anything, check for stored fault codes, vacuum leaks
and any other engine tune components.

Thomas

Incorrect temperature input can cause idle issues... if your OBD2
scanner can read sensor values, you can monitor that.

Here are some common DLC locations:

http://www.ross-tech.com/vag-com/cars/dlc.html

It could be in the center console before or after the hand brake.

Thomas

I forgot to ask what type of fuel injection system your 1.8 uses.

Sounds like a Euro model. Does it have a motorized throttle body?

If not, then the throttle adaptation does not apply.

Thomas

Sorry about the late reply... had to run an errand.

If it is motorized, then yes, the ECM/ECU should be able to re-adapt
to an idle that will be normal... IF the cause of the Idle is due
to a throttle alignment / position issue.

Usually after cleaning & before adapting the ECM, the idle will be
too high (this is with the battery always connected).

When battery is disconnected or the voltage is too low during
start-up, then the idle can start to misbehave.

A sample of a motorized throttle body in action...

http://www.youtube.com/watch?v=pzKD0lu6iqs&feature=plcp

...the part that moves on its own is the throttle being moved by
the ECM to maintain correct idle.

If the problem persist for too long, then you will have to see if
an adaptation via scan tool will solve your issue.

If the alignment does not cure the issue, then you will need to
check for other causes.

Thomas

Sounds liek the Idle air control valve needs replacement.

Are you talking about the Throttle Body?

Yes, I believe, now looking at the entire conversation as for some reason it was not showing previously, what was referred to as the "learned throttle adapter" may be the same thing as a throttle position sensor and could be the problem. They do have to be calibrated after installation. I calibrate them with a multi-meter, but if there is an ECM program to have them learn their position then follow that.
The idle air control valve works like a, "choke" and keeps the idle steady depending on;
whether the engine is warmed up or not
engine load
trhottle position and accessory load

So, they do go hand in hand a bit. One can go bad and affect the other. But if your problem gets better with temperature I would say its the IACV. If you want to check it you can remove it and keep it connected, then turn to key to the run or start position the see if the plunget moves. The plunger opens and closes ports on either side of the butterfly valve of the throttle body to keep the idle steady. So, if you replace make sure they are clean by spraying brake cleaner from the outside in towards the iner throttle body. The keeps deposits from going farther in towards the IACV and pushes them into the throttle body bore where they can be removed. Then I would run a can or two of BG44K, which you can only find at car dealerships, as it is the best fuel system cleaner on the market. In fact plan to change your oil after using it, it may also affect performance as it cleans out gunk. But it will all straighten out for the better, as the deposits all end up in your motor oil if the don't get blown out the exhaust.

After looking into this more it sounds like the IACV is taken in as part of a function of the motorized throttle body. Meaning the idle is kept steady with the ECM and the motor alignment. It sounds like the main issue is finding out how to calibrate the motorized butterfly valve after cleaning it.
I have not had time to look at the you tube video. I don't have the specifications for that model as it is Euro and not in our manuals.
So, I would have to go off of what I could find on youtube.
I also really think that running BG44K will help tremendously. The only thing with some older computers is the time or mileage is takes to sort out changes in the engine. So, give it up to an hour of drive time to sort itself out and make adjustments before you evaluate what the car is doing. The ECM can be really slow to catch up.

The throttle controlled IA is just a guess on my part as the North
American 1.8T engine uses a cable & motor throttle.

So I assume that your engine (non turbo) uses the same.

I need to know the engine code so I can provide engine spacific info.

Not knowing the version of Fuel Injection System that is in you
vehicle, leaves me to just guess what the problem might be.

The engine code is a 3 letter code on the timing belt cover. AEG, BRM, AVH as some examples.

Thomas

Thanks for your help Thomas.
I always get frustrated when I find that the customers' car is a euro spec that we don't have information on. So I really apreciate your helping out. You saved the day.
Thanks

Don't buy a new / used throttle body unless you determine that it
actually is bad. Again, it was just a guess on my part, that the
throttle could be at fault.

Now that I know that it is the ADR engine, I will look for & post
some information that you can use for testing.

Give me some time to find the info.

Thomas

Print & read-through the following pdfs. Perform the tests that
you can with a multi meter (voltage & resistance tests).

You will need a scan tool capable of "deeper" communication than
just a OBD2 code reader, to be able to do "output tests" & Throttle
Adaptation.

Since the problem only occurs in the morning, try starting the car
with all ACCESSORIES off (heater, a/c, lights, seat heaters etc)
to reduce the "electrical load" on the engine. To see if this helps.

The manual I have has 100's of pages which I could print & post, but
that would be too much for you to read through.

Thomas

One more thing. You said:

"On start up without gas the car will die".

Keep in mind that on a fuel injected engine, all you can do is add
more AIR by steeping on the gas pedal. The ECM adds more fuel
when it sees an increase in air flow & gas pedal movement.

Viewing engine sensor inputs when cold, would help you a lot to
possibly determine what is going on.

You can also try do disconnect the MAF sensor (Air Mass Meter #8) to see if it is
possibly at fault.

Keep in mind that any sensor you disconnect, will set a trouble
code that you will have to clear. But that's OK, you are simply
looking for something at will improve your "cold start" operation.

You may have to wait until the following morning to see if there
is a change for the better.

If all else fails, leave it at a VW Service Shop over night and
ask them to only spend 1/2 hr max on diagnosis. Since it runs
fine after a few minutes of initial start up, they probably won't
find anything either after that time because the window is just
too narrow.

Vacuum leaks, fuel pressure, dirty injectors. All can cause issues
such as you listed and can be eliminated / ruled-out as the cause
with the right tools / equipment.

Thomas