[s-cars] Running rough

[Adrian Hart]

I've been experiencing a flat-spot at around 3000rpm ,and my MAP 
reading at idle has dropped from 0.5bar to 0.3 or 0.4. Another problem 
(I thought I had fixed by replacing the plugs and connectors but have 
not) is that there is an intermittent and severe misfire. The car will 
run sweetly, then suddenly lose a lot of power and run with throbby 
"boomy" exhaust noise. This might continue for several miles then 
suddenly everything will come back to normal and away we go. The 
problem *might* be initiated when I hit a rough bit of road, possibly 
indicating some sort of dodgy connection? What's the deal with the 
coil-packs? Are they strictly go/no-go or are they capable of 
functioning intermittently? ALso it tends to initiate when the engine 
has been put under load at low RPM. Supporting facts are a petrol smell 
in the engine bay when running like this and stinky exhaust.

Any help here greatly appreciated.

Adrian Hart.