Idle problem maybe solved

[Alexander Popov]

Glad to hear it’s sorted. 

You would be surprised what a difference even a tiny “hole” can make to the way an engine runs. Had a problem with a 944 Turbo, which was idling at stupidly high rpm following a HG failure and subsequent rebuild. Turned out that cylinder one inlet manifold tract wasn’t fully seated against the mating surface of the head, thus letting in unmetered air... You could barely sneak in a feeler gauge through the “slot”... Similar story years ago with an E30 M3, which had a perished rubber below between the barn door air floor sensor and intake manifold. Same story - rubbish idle, difficult starts and lack of throttle response. £30 later the car was reborn...

Sent from my iPhone

> On 6 Sep 2019, at 19:31, Michael Parris <michaeljparris at gmail.com> wrote:
> 
> Back to my idle/cold start/hot start problem.
> 
> I found the vacuum line to the charcoal canister diverter valve was not plugged in. Obviously that's going to be letting in un-metered air and as the O2 doesn't work until it's warm and can compensate means before that happens there's too much air.
> I'm not really sure how much additional air a little line like that can let in but now I've plugged it back in the car starts from cold without throttle and stays running.  I only ran it for 5 to 10 minutes at idle until the temperature was about quarter of where it normally is, left it an hour and started it again without throttle and it was fine.
> Actually the first time I started it after plugging the line in it ran for about 10 seconds then suffocated and died (or seemed like it), started it straight away and it ran OK if a little wobbly for about 20 seconds.  I'm wondering if it was running a previous 'more air' adaptation to start with and suddenly with less it couldn't run. 
> 
> I'll try again from cold tomorrow just to check it wasn't a fluke.
> 
> Mike
> 90S4 
> 
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