Fired up my car earlier, its been sat for a few days in my garage and thought id take it for a spin. Soon as it started the whole car was shaking like it was misfiring. After the sai pump switched off it was fine and went back to normal revs. Is it safe to say its the sai pump knackered? Iv been meaning to remove it for a while now but not got round to it.

sometimes the sai gets water in the pipes which it pumps around the system causing general mayhem. See what it does when you use it regularly. They got the initials wrong for the sai system, they should have called it pia.

How does it manage to get water in. It takes air from my airbox? I dont use it often as its abit of a toy lol. Iv just clocked 1k since i got it in February.

When the sai pump rivets start to break up, the casings let a crack form into which any water from puddles or damp condensation cant wait to run down into.

So if that's happened water is being thrown into the cylinders on startup?

This must happen in my opinion, as when I changed my noisy sai pump, about an eggcup of water ran out of the corrugated plastic pipe when I removed it.

 

There are quite a few youtube vids that detail diagnosis on this system that mention it too.

 

That being said, the combi valve does inject air into the exhaust ports rather than the cylinders, but even so, can't do much good to a stone cold block.