Idle RPM tendency to increase with outside temperature (MFI)

2.0E stock MFI.
Everything was perfectly tuned this winter : dwell, timing, idle spot on at 900/950 RPM with a CO at 3% :)

Outside air temp around 10°C :

Attachment 636716


Last week-end, weather getting hot in my area, around 25°C and now the idle RPM increased to 1050...

Attachment 636717


Of course oil temp increases with the OAT, and my understanding is that explain why the idle RPM increases also.

What advice would you give :
stay like that ?
Close at little bit the 6 idle screws ?
reduce a little the advance ?

Thanks !

What is the condition of the throttle bodies? Have they ever been refurbished? If so, how long ago

NOS TB, replaced a year ago.
What I’ve described is normal I think, my concern is should I leave it like that or should I correct it !

I would call that normal for the ambient temperature and thus slightly hotter engine temp. Just tweak the bypass screws a little to what ever speed you want.

Quote:

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Originally Posted by edmayo

I would call that normal for the ambient temperature and thus slightly hotter engine temp. Just tweak the bypass screws a little to what ever speed you want.

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Thanks Ed, I was just curious if other owners were observing the same behavior !

As another MFI owner, yes idle will wander. You may have to search my user name as, ironically, mines in a shop for MFI work and rear bushings. It will probably be a few weeks before I get it back for an update. My best guess is 90 something K on the MFI pump. Motor will go into a dyno shop, which Ed probably knows of. Read the Rice paper about MFI's you can find here. There's another thread about 'sputter' in the 4-5K range. My advice is stick with 6k rpm versus the 7 I have. Spun a main bearing way back when.