On Friday Ruby wouldn't idle when I started her. I had to hold the throttle open to get her to keep running. When I got to the first stop, she quit and had to be restarted.
I threw 128 ml of Moreys injector cleaner in a full tank and it fixed her.
I suspect a blocked vacuum hose (you know, the dreaded 5-way connector syndrome). I know fuel doesn't flow through there, but Moreys is a potent volatile cleaner, and I think the fumes did the trick.
Any which way, I'm a believer. It's cheaper than the other injector cleaners and you need less in a tank.
Could be worth trying in the above case. I personally can't see how a coolant problem would cause the revs issue.
Moreys won't do any harm, and your injectors will sparkle in the sunlight!
Supercheap Auto have it.