I was very lucky to get the opportunity to get out in my 500 on this roasting hot day...25 C even here in The Highlands of Scotland. We were rescuing my modern car as I had to exchange the wrong brake pads at the motor factors.
Murphio ran like a dream as always. But once hot, when approaching lights and roundabouts, the tickover seemed to drop down and I could only avoid stalling by blipping the throttle.

I have increased the tickover speed but I hope it won't be too high now when cold. I may be doing a 250 mile run tomorrow, so that will test things, but has anyone else had this, ahem, (I hate to say this regarding Murphio), problem?

I would imagine Peter all you have experienced the fact that the outside air is considerably hotter, hence the cooling on air cooled engines is going to suffer.

Engine is going to run hotter therefore there will be a higher chance of fuel vaporisation, especially when at tickover when sitting at lights and there is no airflow.

I know there is the old adage well they run in hotter places like Italy alright but it doesn't necessarily mean there is anything wrong with the car, just a different setup for different climatic conditions. UK when it is really hot seems to be much more humid that the many Mediterranean countries.

Down south yesterday was like walking around inside an oven. I opened the back door to my van and was hit with a blast of heat. The outside temp gauge said it was 39° and that did drop to 36° but pretty much stayed there all day.

In my experience of daily use 500's have erratic idle speeds at the best of times, at worst totally unpredictable when very hot.

Just a thought from a comment passed to me the other day. Whilst down visiting my mum, I managed to spend a day (and got a right royal bollocking for being away a LOT longer than I had envisaged, and my phone was switched off!!) with a guy who specialises in tuning and restoring 500s. He recommended that I use 'super' petrol as it has (supposedly!) less Ethonal in it. My thought is this---how many REALLY hot days do we have in the UK vis-a vie Italy?--is the fuel in Italy different to allow for this? Oil companies change the additives for summer/winter use, so would it be possible that in Italy AGIP put in additives to aid running in very hot weather? Just a thought!

I did use "Super" for a while, when fuel prices went "low" and the car did run nicely on it; I will try again and report back.
I ran out of lead additive a few weeks ago and didn't get any more, so on a similar thought, I might try that again.
But I think I found the real cause........Stopping to photograph a beach on the West Coast I got talking to an old chap who seemed to have a definite affinity with the car, asking really sensible questions and admiring it for what it is....more than just a pretty shape. So of course I showed him the engine, and the the air-cleaner lid was sitting in place, but with the clips undone. I re-fastened them and at the service station later I noticed the lid loose again. I "modified" the front clip but it still came loose. With a bit of card wedged under the clip it seems OK now.

I know about the three clip mod that some people do which apparently is on the 126, but for now I am going to drill two tiny holes in the lid and wire it through the clip holes...belt and braces.

The engine has only stalled once since then and that was when a numpty forced me to stop quickly on a single-track road having sailed past the passing place. In fact, tickover needs reducing a little from my overtightening.

I'm confused. For those of us with a 650 engine and 3 clips are you saying a 500 engine only has 1 clip?

Paolo66 said:

I'm confused. For those of us with a 650 engine and 3 clips are you saying a 500 engine only has 1 clip?

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The 500 has two clips but I couldn't be bothered fiddling with the rear one on the roadside.

fiat500 said:

I ran out of lead additive a few weeks ago and didn't get any more, so on a similar thought, I might try that again.

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I have a couple of bottles here I won't use that I can post to you. Drop me a PM with your address.

cheers, Steve

fiat500 said:

The 500 has two clips but I couldn't be bothered fiddling with the rear one on the roadside.

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So we're the 2 clips I assume opposite each other? My 500 engine has always had 3 clips equally spaced around the air filter which I thought was the norm?

You learn something new everyday!

Vitesse said:

So we're the 2 clips I assume opposite each other? My 500 engine has always had 3 clips equally spaced around the air filter which I thought was the norm?

You learn something new everyday!

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Yes and just realised where i found the info...
http://fiat500club.org.uk/home/technical-article-filtering-out-the-noises/

So thanks to Quentin and the Fiat 500 Club.

fiat500 said:

Yes and just realised where i found the info...
http://fiat500club.org.uk/home/technical-article-filtering-out-the-noises/

So thanks to Quentin and the Fiat 500 Club.

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Crumbs that's taking originality to a new level. I thought I was pedantic!!!!