Lumpy Engine

[debaron]

Been having a problem with my 400 Chim for a while now. Have posted stuff on earlier threads and tried all the advice given but still got it!

It's a vibration and lumpyness in the engine at around 2000 rpm like it's low fuelling a cylinder. Some times it's worse - sometimes it's not there at all! tends to get more noticeable after an hour or so on the motorway.

Tends to 'come or go' only when starting the engine though. - ie - I can be going along fine, pop in to get some petrol. Switch off - Start up - LUMPY! It will tend to stay like this then. It can also go the other way. And before the engine even comes to life I can tell whether it's going to be lumpy or not - I can feel it while the starter is cranking! This would then suggest a mechanical problem though....

When it is running, you can hear it too as a slightly different tone from the exhaust. It's like a misfire i guess but have been over the leads, plugs, rotor and HT numerous times. Only thing not changed is those plug boot extender things and the coil.

I'm on to thinking it's a fuelling problem now - dirty/leaking injector or possibly something in the top end mechanicals? Maybe a fuel pressure regulator on the way out.....It's the intermittentcy of it all that pisses me off - I wish it would either do it all the time or not at all!!!!


Next stop Mark Adams if I can't cure it!

Any advice gratefully received.