88 528e races at cold start...

Hi gentlemen,

I wonder if somebody has an idea what I can do to fix this myself.
At cold start in the morning the engine races, and it takes a while to
calm down, to get to normal idle speed. After that, it restarts fine
and at proper speed. Is there a sensor that can give a bad reading to
get such high engine speeds? Coolant level is fine, and i have no
vacuum leaks as far as I can tell.
Could it be in the computer perhaps? But I feel it must get the
request to run very fast from some place.
I really would appreciate any help I could get.
In the last while I have started it after cranking it with a
deliberately entered false code, to get the oil circulating before I
fire it up with the proper code.

Sincerely, Frank H.

BMW's do run at fast idle - about twice unloaded warm idle when cold - for
30 - 60s after starting.

Having the AC on also increase the warm idle by about 200rpm.

Precise idle speed depends on engine smaller engines generally idle faster
than large ones.


"Frank H" > wrote in message
...
> Hi gentlemen,
>
> I wonder if somebody has an idea what I can do to fix this myself.
> At cold start in the morning the engine races, and it takes a while to
> calm down, to get to normal idle speed. After that, it restarts fine
> and at proper speed. Is there a sensor that can give a bad reading to
> get such high engine speeds? Coolant level is fine, and i have no
> vacuum leaks as far as I can tell.
> Could it be in the computer perhaps? But I feel it must get the
> request to run very fast from some place.
> I really would appreciate any help I could get.
> In the last while I have started it after cranking it with a
> deliberately entered false code, to get the oil circulating before I
> fire it up with the proper code.
>
> Sincerely, Frank H.

I have had normal idle for over 10 years before this racing idle speed
started.
2300rpm at cold start is too high I believe.
Something is not right. Which sensor could cause this?

Cheers, Frank

On Sun, 5 Apr 2009 13:32:34 +0100, "R. Mark Clayton"
> wrote:

>BMW's do run at fast idle - about twice unloaded warm idle when cold - for
>30 - 60s after starting.
>
>Having the AC on also increase the warm idle by about 200rpm.
>
>Precise idle speed depends on engine smaller engines generally idle faster
>than large ones.
>
>
>"Frank H" > wrote in message
.. .
>> Hi gentlemen,
>>
>> I wonder if somebody has an idea what I can do to fix this myself.
>> At cold start in the morning the engine races, and it takes a while to
>> calm down, to get to normal idle speed. After that, it restarts fine
>> and at proper speed. Is there a sensor that can give a bad reading to
>> get such high engine speeds? Coolant level is fine, and i have no
>> vacuum leaks as far as I can tell.
>> Could it be in the computer perhaps? But I feel it must get the
>> request to run very fast from some place.
>> I really would appreciate any help I could get.
>> In the last while I have started it after cranking it with a
>> deliberately entered false code, to get the oil circulating before I
>> fire it up with the proper code.
>>
>> Sincerely, Frank H.
>

In article >,
Frank H > wrote:
> I have had normal idle for over 10 years before this racing idle speed
> started. 2300rpm at cold start is too high I believe. Something is not
> right. Which sensor could cause this?

Assuming it's an injection engine check for air leaks round the inlet
system first. Unlike carburettors, these cause a fast idle.

--
*If all the world is a stage, where is the audience sitting?

Dave Plowman London SW
To e-mail, change noise into sound.

Thanks Dave,
I will check for a vacuum leak tomorow.
If I can not find any, it is time to check out various sensors.
It is injected, and it has run perfectly for the last ten years or so.
Not time for a new one yet.

Cheers, Frank





On Sun, 05 Apr 2009 22:36:59 +0100, "Dave Plowman (News)"
> wrote:

>In article >,
> Frank H > wrote:
>> I have had normal idle for over 10 years before this racing idle speed
>> started. 2300rpm at cold start is too high I believe. Something is not
>> right. Which sensor could cause this?
>
>Assuming it's an injection engine check for air leaks round the inlet
>system first. Unlike carburettors, these cause a fast idle.

"Dave Plowman (News)" > wrote in message
...
| In article >,
| Frank H > wrote:
| > I have had normal idle for over 10 years before this racing idle
speed
| > started. 2300rpm at cold start is too high I believe. Something is
not
| > right. Which sensor could cause this?
|
| Assuming it's an injection engine check for air leaks round the
inlet
| system first. Unlike carburettors, these cause a fast idle.
|
| --
| *If all the world is a stage, where is the audience sitting?
|
| Dave Plowman London SW
| To e-mail, change noise into sound.


Um, I'm no expert on foreign vehicles, but if it's injected, there is
probably an Idle Air Control valve just like or similar to injected
vehicles made by G.M.

If the IAC is toast (and stuck in one position), it would cause the
same exact symptom as a vacuum leak.

Spraying WD-40 around any potential areas that could be leaking should
help discover if you have a vacuum leak. Using carb cleaner would be
OK around metal, but would further dry out rubber hoses.

Also, on a vehicle that is 10 years old, checking the vacuum hoses
would be a good idea and would be a very likely source of a vacuum
leak. Spraying WD-40 or on the hoses would yield the same discovery
if there is a leak.

1. Check vacuum hoses - use WD-40 to help diagnose
2. Check for vacuum leaks around gaskets - again use WD-40
3. Check and replace (if necessary) the IAC valve ( or step motor) -
whatever it's called on BMW's

Good luck. Give us a report on what you found when the vehicle is
repaired.

--
Steve Spence
Independent AMSOIL Dealer
AMSOIL - The "Once A Year" Oil Change
Unemployed Car Guy - Trying To Earn A Living
35 Years of G.M. Parts Experience
URL: http://synthetic-oil-tech.com/1690163
Email:

Thanks Steve,
That is good advise with the WD-40.
Will follow your outlined procedure and let's see if I can find the
culprit.
I'll post a follow-up, once it is rectified. Might help someone else
as well.

Cheers, Frank
..
On Sun, 5 Apr 2009 17:31:23 -0500, "Steve" >
wrote:

>"Dave Plowman (News)" > wrote in message
...
>| In article >,
>| Frank H > wrote:
>| > I have had normal idle for over 10 years before this racing idle
>speed
>| > started. 2300rpm at cold start is too high I believe. Something is
>not
>| > right. Which sensor could cause this?
>|
>| Assuming it's an injection engine check for air leaks round the
>inlet
>| system first. Unlike carburettors, these cause a fast idle.
>|
>| --
>| *If all the world is a stage, where is the audience sitting?
>|
>| Dave Plowman London SW
>| To e-mail, change noise into sound.
>
>
>Um, I'm no expert on foreign vehicles, but if it's injected, there is
>probably an Idle Air Control valve just like or similar to injected
>vehicles made by G.M.
>
>If the IAC is toast (and stuck in one position), it would cause the
>same exact symptom as a vacuum leak.
>
>Spraying WD-40 around any potential areas that could be leaking should
>help discover if you have a vacuum leak. Using carb cleaner would be
>OK around metal, but would further dry out rubber hoses.
>
>Also, on a vehicle that is 10 years old, checking the vacuum hoses
>would be a good idea and would be a very likely source of a vacuum
>leak. Spraying WD-40 or on the hoses would yield the same discovery
>if there is a leak.
>
>1. Check vacuum hoses - use WD-40 to help diagnose
>2. Check for vacuum leaks around gaskets - again use WD-40
>3. Check and replace (if necessary) the IAC valve ( or step motor) -
>whatever it's called on BMW's
>
>Good luck. Give us a report on what you found when the vehicle is
>repaired.

On Sun, 05 Apr 2009 22:36:59 +0100, "Dave Plowman (News)"
> wrote:

>In article >,
> Frank H > wrote:
>> I have had normal idle for over 10 years before this racing idle speed
>> started. 2300rpm at cold start is too high I believe. Something is not
>> right. Which sensor could cause this?
>
>Assuming it's an injection engine check for air leaks round the inlet
>system first. Unlike carburettors, these cause a fast idle.

But, he says once the engine has warmed up the idle rpms are normal. Further,
if the engine is warm, a restart does not produce the fast idle condition.

I suppose an intake manifold leak *might* "heal" once the head has heated up,
but it seems much more likely there's an engine temperature sensor that has
gone to Heaven...

In article >,
daytripper > wrote:
> On Sun, 05 Apr 2009 22:36:59 +0100, "Dave Plowman (News)"
> > wrote:

> >In article >,
> > Frank H > wrote:
> >> I have had normal idle for over 10 years before this racing idle speed
> >> started. 2300rpm at cold start is too high I believe. Something is not
> >> right. Which sensor could cause this?
> >
> >Assuming it's an injection engine check for air leaks round the inlet
> >system first. Unlike carburettors, these cause a fast idle.

> But, he says once the engine has warmed up the idle rpms are normal.
> Further, if the engine is warm, a restart does not produce the fast idle
> condition.

> I suppose an intake manifold leak *might* "heal" once the head has
> heated up,

That was my guess.

> but it seems much more likely there's an engine temperature
> sensor that has gone to Heaven...

I'm not certain what variety of injection was fitted to that model. Some
early systems didn't have ECU controlled idle. But I'm sure some searching
should give details of how it works on that particular one.

--
*When blondes have more fun, do they know it?

Dave Plowman London SW
To e-mail, change noise into sound.

daytripper > wrote:
>On Sun, 05 Apr 2009 22:36:59 +0100, "Dave Plowman (News)"
> wrote:
>
>>In article >,
>> Frank H > wrote:
>>> I have had normal idle for over 10 years before this racing idle speed
>>> started. 2300rpm at cold start is too high I believe. Something is not
>>> right. Which sensor could cause this?
>>
>>Assuming it's an injection engine check for air leaks round the inlet
>>system first. Unlike carburettors, these cause a fast idle.
>
>But, he says once the engine has warmed up the idle rpms are normal. Further,
>if the engine is warm, a restart does not produce the fast idle condition.
>
>I suppose an intake manifold leak *might* "heal" once the head has heated up,
>but it seems much more likely there's an engine temperature sensor that has
>gone to Heaven...

Nope, temperature sensor doesn't affect that at all. About the only
reasonable possibilities are a vacuum or intake leak or a gunked-up
throttle that won't close, or a gunked-up idle control valve. Certainly
wouldn't help to clean the idle control valve and clean the throttle body
as well. You should do that every few years for preventative maintenance
anyway.

You'd think that the throttle position switch would be able to cause this
sort of effect too... but in reality it doesn't seem to. Disconnect the
switch and verify for yourself that the behaviour doesn't change, though.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."