Capri - Poor Idling

My white XL Capri has not been running very smoothly of late, especially idling roughly.
I did the usual things like checking all the leads and connections but no difference. With the engine running, I started pulling off the ignition leads & to my surprise when I removed the lead to No 1 cylinder, it made no difference. When the other cylinder leads were removed, you could really notice the difference. So, it was No 1 cylinder that was the problem.
First fix was to replace the ignition leads & the spark plugs. The leads had not been replaced in a long while so I thought replacing both of these items would fix the problem.



So with the new ones in place, I started the engine & no real difference. Pulling the lead from No 1 cylinder when idling & again it made no difference. So, what was the problem? I had read that air leaks around the inlet manifold may be an issue but after checking all the hoses & connections, again there was no difference.
Then looking around again with a torch, I noticed that the inlet manifold gasket was split right on the end near the No 1 cylinder inlet port. It was like a tear in the gasket. So was this the problem? The only way to find out was to replace the gasket. The photos show the damaged gasket as the split went right through the edge of the gasket. Look at the right hand lower section of the gasket. On removal of the manifold, it seem as if the gasket was also covering part of the inlet port.

 

Removing the inlet manifold is a real pain!!! The two bolts underneath require a narrow socket to remove them. What made mine really difficult was that last time I had the manifold off I had to replace the centre bottom bolt with a different size head (the other 4 are all 1/2 inch). After spending ages to work this out, it soon came out with the correct size socket.
Luckily I had a spare ACL gasket so on it went. Again, tightening the bolts underneath is not all that easy. So, after reconnecting everything, refilling the radiator as when the manifold came off, a bit of fluid was lost around the water jacket.
OK, now time to turn the key. Yes, much smoother & running really well and idling much better.I did not realise that such a split would allow so much air to enter the system and cause it to run roughly.
End of story so make sure you check for air leaks if your car is sounding a bit sick.
(Click on the photos to enlarge)