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

Tiny
GALVA
  • 1998 AUDI 100
  • 100,000 MILES

I recently had to recharge my battery which I removed from the car first. Car seems to drive fine after its warm but when the clutch is used when cold it will stall

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Friday, October 5th, 2012 AT 4:06 PM

27 Replies

Tiny
EXOVCDS
  • MEMBER

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

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Friday, October 5th, 2012 AT 5:28 PM
Tiny
GALVA
  • MEMBER

Thanks for the quick reply. The car is a 1.8 cabriolet. I have cleaned the throttle body but do not know about the adaption or alignment via scan tool. I have a basic OBD2 scanner but have been unable to locate the port on the car. I dont know if it is the old type. Is it possible it could be the engine coolent sensor or the pvc valve. Thanks for your help

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Friday, October 5th, 2012 AT 5:37 PM
Tiny
EXOVCDS
  • MEMBER

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

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Friday, October 5th, 2012 AT 5:42 PM
Tiny
EXOVCDS
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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

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Friday, October 5th, 2012 AT 5:44 PM
Tiny
GALVA
  • MEMBER

Hi when I cleaned the throttle body it has a motor underneath that controls the butterly valve. This must still work if it idles when warm, is this right? Does it having a motor mean that the ECU may correct the fault in time.

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Friday, October 5th, 2012 AT 7:08 PM
Tiny
EXOVCDS
  • MEMBER

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

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Friday, October 5th, 2012 AT 8:13 PM
Tiny
DRCRANKNWRENCH
  • EXPERT
  • 3,449 POSTS

Sounds liek the Idle air control valve needs replacement.

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Friday, October 5th, 2012 AT 11:58 PM
Tiny
EXOVCDS
  • MEMBER

Are you talking about the Throttle Body?

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Saturday, October 6th, 2012 AT 12:07 AM
Tiny
DRCRANKNWRENCH
  • EXPERT
  • 3,449 POSTS

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.

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Monday, October 8th, 2012 AT 5:32 PM
Tiny
GALVA
  • MEMBER

Hi in reply to the last thread, first of all thanks for all the help. I would like to check the iacv. It sounds like you are saying this is in the throttle body housing? I've checked the intake to the tb and theres no electric connections. Could you help me locate the iacv so I can check and clean it. Occasionally on start up instead of dying it revs itself from 1000 rpm to 1500 rpm over and over. Is this another symptom?

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Friday, October 12th, 2012 AT 2:53 PM
Tiny
DRCRANKNWRENCH
  • EXPERT
  • 3,449 POSTS

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.

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Friday, October 12th, 2012 AT 4:30 PM
Tiny
EXOVCDS
  • MEMBER

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

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Friday, October 12th, 2012 AT 4:50 PM
Tiny
DRCRANKNWRENCH
  • EXPERT
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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

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Saturday, October 13th, 2012 AT 5:20 PM
Tiny
GALVA
  • MEMBER

Hi the car is a 1.8, 5 valve engine no ADR429276. Today I got a new temp sensor as I have read a few threads saying this solved the problem. Also on my a4 1.8 turbo which I know from experience if the temp sensor goes on that car the temp gauge fails to work, the choke doesnt work and the radiator fans run contantly. Anyway the new sensor didnt do anything even though thay are a very similar car. There is another temp sensor next to the one I replaced. 1 is green 4 pins but only 2 wires which I replaced the other is gray 3 pins and 3 wires which I might replace next. After this I will remove the throttle body again and take apart the electric motor on the bottom and clean test etc. If this doesnt work I have seen replacements which fit 95 -01 a4s used for 50. I will post to give results. As always any advice on anything is grately appreciated. Thanks steve

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Saturday, October 13th, 2012 AT 6:06 PM
Tiny
EXOVCDS
  • MEMBER

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

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Saturday, October 13th, 2012 AT 6:13 PM
Tiny
GALVA
  • MEMBER

Thanks Thomas I appreciate all your help. I forgot to say that I have covered just under 100 miles sinse I cleaned the throttle body. On a cold start now it maybe only takes a few minutes of me holding the revs at 2000 rpm or driving to the end of my street and the car will then idle on its own. I dont want to build my hopes up and say I think the ECU maybe correcting the idle quicker but the problem remains. On start up withot gas the car will die.

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Saturday, October 13th, 2012 AT 7:19 PM
Tiny
EXOVCDS
  • MEMBER

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

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Saturday, October 13th, 2012 AT 7:29 PM
Tiny
EXOVCDS
  • MEMBER

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

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Sunday, October 14th, 2012 AT 3:44 AM
Tiny
GALVA
  • MEMBER

Thanks for your help, I will go through the info you sent and hopefully uncover the problem. I do have another problem also, I dont know whether I need to start a new thread or not but I think it might be something you can help with. About 5 months ago I narrowed a power leak to fuse 4. This seems to power the interior lights, stereo, lighter, digital clock and alarm system. I use the car with no fuse 4 in which is a 15amp. I sometimes read somewhere a new thread which will give me hope in finding the leak but Im always diappointed. I have unplugged the componants using fuse 4, got a new battery and had the alternator checked. I cant seem to locate an accurate diagram and have tried to trace wires and look for damaged cables. I have kind of got used to no music and interior lights etc im sure someone somewhere has had a fault just like this and knows an area prone to damage wires or a device that I havnt thought of which uses to much energy when its faulty. This problem mey even be more annoying then the original 1 im trying to solve. If you can shed any light on this problem or advise on where to look for an answer or even a wiring diagram so I can test wires and run my own this would help greatly. Thanks Steve

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Sunday, October 14th, 2012 AT 1:18 PM
Tiny
GALVA
  • MEMBER

Sorry forgot to say how much power is been lost. If I hold the volt meter on the battery and wait I can see the voltage drop. If I put fuse 4 in and leave the car 5 hours it wont start.

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Sunday, October 14th, 2012 AT 1:29 PM

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