NL 3.5 SOHC idling low

[Dexter]

Hey guys,

The last week I got a little ambitious and decided to replace my plugs, I got half way through taking the manifold off and decided that I would leave it for when I get my next service. So I bolted everything back up and put all the hoses back on, reconnected the battery and she started up fine. Then left her as she was... Last night I started her up and she idled fine while she was cold, then she warmed up and took her for a drive, once warm the revs were dropping very low, even stalled once or twice. She has never done this before, so I was a little alarmed so I stopped and double checked everything, all looked well so I continued, after a good 10 minutes drive she was idleing happly all be it at about 500-750 rpm? Is this too low and any ideas what could cause the change, she still idles up when I turn on the air con.

Any ideas?

[NJV6]

Mine idles about 750ish when warm

1200 when cold

[Dexter]

Interesting, maybe I had a little airleak that was causing it to idle high previously, was wondering if disconnecting the battery for that long would have had any effect. I know some cars have a learning computer that adapts to a few things and all this is forgotton after a long period of time without power.

[NJV6]

Yes, mine idles a little erratic for a short while after taking the battery off.

[Dexter]

Excellent, as always you are a wealth of knowledge.

[NJV6]

On the DOHC there can't be any air leaks as the idle circuit is all done by the stepper motor which is moulded into the throttle body.

What is really worthwhile is taking the throttle body off (5 bolts I think) and giving it a super clean with carb cleaner or throttle body cleaner. The black crud just comes off, the stepper motor is known for dodgy behaviour from the gunge in the inlet.