why is my excel reving its head off at idle?

[websteg]

Bought a 2nd hand automatic excel for $1500 with 98,000km. Thought is was a bargin, but snapped the exhaust camshaft at the 2nd journal almost straight away. Engine was sludged and not feeding oil to the camshaft properly.

Bolted up a 2nd hand head, timed it as best as I could. Turned the key and it fired up instantly, but was reving hard. Checked the throttle cable, gave it a few blips, still reving hard. Didnt mess around with the injection or induction system or anything excpet for unbolting/rebolting the inlet manifold. It runs smoothly, so dont think its the timing, but revs way to hard and I cant knock it back to a comfortable idle.

What have I done wrong and how to fix?

[fro]

I'd be looking for an air leak around the manifold. Sounds like the symptoms.

[Bevan-L]

SOHC or DOHC? My DOHC engine done exactly the same thing when the idle control unit got a crack in it and was sucking in air

[websteg]

DOHC. What/where is the idle control unit?

[Mooa42]

I had a similar problem with mine (twin cam) and the plugs that go to the throttle position sensor and the idle control unit are the same and I had mine reversed. So try swapping them and see what happens. It won't do any damage as I ran mine the wrong way in an event and didn't have any issues.

(the plugs are near where the rubber air cleaner joins the throttle body)

[websteg]

Problem found and solved. Checked throttle body butterfly, looked ok. Pulled all the sensor plugs off one by one, made no difference. Checked inlet induction manifold nuts, gave them a few turns, revs returned to normnal. I had them pretty tight, but as I was being poverty and re-using gasket, they needed more presemuably as the gasket material was semi-compressed from last fitting. Serves me right for not spotting a new gasket. Thanks for the help.