1.6 Sigma running very rich after cap popped off. Ideas?

[JW027]

Roadsport was running fine until a small black cap popped off just before Graham hill bend @ Brands. When the cap was off the engine would rev up to the limiter. This is the cap: It the same as the one below the air filter.



We replaced the cap and fixed it place with a jubilee (it just sat on before) but now she runs very very rich. I checked and replaced the plugs and they are covered in soot


I'm totally stumped but no nothing about this engine or what the cap does but after that it's all gone wrong.

Can anyone give me a helping hand with some advice/knowledge?

[nigelpugh7]

Does your sigma car have the oil catch tank fitted?

On my sigma 135, it came without it at first, and the place where the cap came off in your picture was connnwdfed by a pipe to the engine PCV.

The kit included the cap you mention and one formthe trottle body too.

Now the pipe from the PCV and the other breather pipe runnto the catch tank.

The cap you mention just stops the plenum breathing in air into the inlet manifold, so choice be capped off as it was before you lost the cap,

I can only think the engine would run rich without it on, with a cap back on it should run normally.

[JW027]

hi Nigel
yes it has it fitted. It's back on but running rich now. Just coincidence? I'm not so sure.

[nigelpugh7]

JW027 said:

hi Nigel
yes it has it fitted. It's back on but running rich now. Just coincidence? I'm not so sure.

Seems like a coincidence then, not sure what else could make it run rich.

One thing to check is that no air is getting around the caps where the jubilee clip tightens around it.

It's actually quite easy to over tighten, and flatten the cap which means air gets in IE down the side.

[sfaulds]

That cap is under vacuum when the engine is running. The only time we've seen them come off is if the car is spun and the engine turned over backwards. Check the air filter for damage or anything else that's been spat out the engine, otherwise the cam timing may have moved.

[cambuscat]

Are you sure it's running rich and not oily plugs? If breathing too much oil then it goes into inlet manifold via that pipe. Catch tank stops this.

[JW027]

Hi Chaps,
The fault causing it to run rich was a very small split in a vacuum hose. Not sure if this had anything to do with the cap or spin perhaps coincidence.

Thanks very much for all your thoughts and willingness to help.

Jed

[nigelpugh7]

JW027 said:

Hi Chaps,
The fault causing it to run rich was a very small split in a vacuum hose. Not sure if this had anything to do with the cap or spin perhaps coincidence.

Thanks very much for all your thoughts and willingness to help.

Jed

Glad you got it sorted! Shame the weather is too poor to go out much!