Can anyone please help me...my disco's idle speed has dropped by approx 100rpm and there's a slight amount of brownish smoke coming from the exhaust. The engines vibrating alot because the idle speeds down, when I rev the engine there's quite a bit of smoke coming from the exhaust also. I've replaced the injectors and checked the lift pump. Also there's a kind of load induction noise coming from the air box, i've tried removing the air intake pipe but still the same noise, checked the turbo also. Does anyone have any ideas as to what it may be, could this be the EGR Valve Stuck Open?????

Worst case scenario, and this is an UNEDUCATED guess, is head gasket. My head gasket failure started off with a drop in idle revs, although I didn't get brown smoke, but white. But I DID get quite a bit of engine vibration. It only took a few minutes of driving for the gasket to fail fully though, so maybe this isn't your problem.

Has yours got an EGR valve? Double check, it's easy to spot, there will be a blanking plate fitted if not.

Thanks for the reply, yes there's an EGR valve fitted. As my engine warms up the idle speed increases, but still smokey whilst reving the engine on my drive. Going to try fitting a blanking plate to remove the EGR system and go from there.

Disc300Series said:

Thanks for the reply, yes there's an EGR valve fitted. As my engine warms up the idle speed increases, but still smokey whilst reving the engine on my drive. Going to try fitting a blanking plate to remove the EGR system and go from there.

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Whereabouts are you? Someone may be able to recommend a really good indepent specialist that could diagnose your problem quickly.

I'm near Durham.