'90 BMW 318i - surging throttle problem

> I have recently aquired a '90 BMW 318i, it has run 230k km and is in
> pretty decent condition.
>
> However, when at constant throttle - regardless of which gear - I am
> experiencing a surging / cycling of the throttle. As a result the car
> goes faster and faster. Well, not _so_ fast. ;-)
>
> The sympthoms are as if I were slowly pressing the throttle down and
> releasing it, ending up at a higher throttle setting than previously and
> repeating it.

First thing I'd check for is a vacuum leak. Possibly a bad gasket on the
far side of the throttle in the intake manifold.

--
Who needs a life when you've got Unix? :-)
Email: , John G.Burns B.Eng, Bonny Scotland
Web : http://www.unixnerd.demon.co.uk - The Ultimate BMW Homepage!
Need Sun or HP Unix kit? http://www.unixnerd.demon.co.uk/unix.html

John Burns wrote:

> First thing I'd check for is a vacuum leak. Possibly a bad gasket on the
> far side of the throttle in the intake manifold.

Thanks for the suggestion, I will try to spray some starter help around
that area and see if the engine revs higher.

--

------------------------------------------------------------------------
Wenn im Zweifel, Volleistung! DoD#2101
'90 BMW 318i When in doubt, floor it!

I have had a similar problem but mine also had problems idling...

found out all it was was a loose air intake pipe... near the air filter.
seems to be not a great connection...

plugged it back on and perfect!

good luck


"BBO" > wrote in message ...
> BBO > writes:
>
>> John Burns wrote:
>>
>> > First thing I'd check for is a vacuum leak. Possibly a bad gasket on
>> > the
>> > far side of the throttle in the intake manifold.
>>
>> Thanks for the suggestion, I will try to spray some starter help
>> around that area and see if the engine revs higher.
>
> Nope, that didn't work either. The search goes on. Might it be the
> airmass meter or could it be the lambda sensor?
>
>
> --
>
> ------------------------------------------------------------------------
> Wenn im Zweifel, Volleistung! DoD#2101
> '90 BMW 318i When in doubt, floor it!

BBO wrote:
> Hello,
>
> I have recently aquired a '90 BMW 318i, it has run 230k km and is in
> pretty decent condition.
>
> However, when at constant throttle - regardless of which gear - I am
> experiencing a surging / cycling of the throttle. As a result the car
> goes faster and faster. Well, not _so_ fast. ;-)
>
> The sympthoms are as if I were slowly pressing the throttle down and
> releasing it, ending up at a higher throttle setting than previously and
> repeating it.

Ok, I took the car into a good independent shop and he did a testrun on
it. No errors showed up. He then removed the hose on the cold side of
the air manifold intake and sprayed some cleaner stuff into the mainfold
intake where there is some kind of valve (not sure of the english word,
sorry) which was full of soot.

That almost cured the problem, and I will repeat the procedure a few
times to get it good and clean.

Apparently it is some kind of idle valve that was stuck causing the
surging.

Cheers,

--

------------------------------------------------------------------------
Wenn im Zweifel, Volleistung! DoD#2101
'90 BMW 318i When in doubt, floor it!

> Apparently it is some kind of idle valve that was stuck causing the
> surging.

Yes, the idle control valve. It's easy to remove and clean.

--
Who needs a life when you've got Unix? :-)
Email: , John G.Burns B.Eng, Bonny Scotland
Web : http://www.unixnerd.demon.co.uk - The Ultimate BMW Homepage!
Need Sun or HP Unix kit? http://www.unixnerd.demon.co.uk/unix.html

John Burns wrote:
>>Apparently it is some kind of idle valve that was stuck causing the
>>surging.
>
>
> Yes, the idle control valve. It's easy to remove and clean.

Yeah, I cleaned that one too, but the stuck valve or gate or whatever it
is called was in the air intake manifold. That is the one that wasn't
closing opening properly.

After I cleaned and WD40'ied the idle control valve the engine idle
became very smooth as well. I like this car. It's fun to drive and
tinker with. :-)

--

------------------------------------------------------------------------
Wenn im Zweifel, Volleistung! DoD#2101
'90 BMW 318i When in doubt, floor it!