hi can anyone help,i have a 1990 420 sel,which for some time has had a slight hesitstion at low throttle openings ,i have replaced all the usual stuff,plugs leads cap etc,but no change,apart from now getting worse sometimes not starting (or firing) then left for 10 mins starts first time?please help!
Since you seem to have been all round the ignition side of things , perhaps the trouble lies with the fuel system ?
It is worth checking the fuel pump relay ( the one with 'kickdown' printed on top } and the OVP relay ( the tall slim one with the fuse on top ) as they can suffer from deteriorating solder joints on the circuit boards ( simple job to resolder ) causing the fuel pumps to operate intermittently . Joints can go high resistance with current passing through which can explain fault clearing when cold but appearing after a few minutes .
Fuel pumps themselves can fail , or suffer corroded electrical connections due to their position under the back of the car , also worth changing fuel filter ( about £10 ) if it has not been done in a while .
Other than that , I'd wonder about a vacuum leak on the induction side of the engine , maybe a perished rubber coupling on a vacuum pipe somewhere ?
These problems can be tricky to trace , but usually are something fairly simple and cheap to fix .
Good luck .
It is worth checking the fuel pump relay ( the one with 'kickdown' printed on top } and the OVP relay ( the tall slim one with the fuse on top ) as they can suffer from deteriorating solder joints on the circuit boards ( simple job to resolder ) causing the fuel pumps to operate intermittently . Joints can go high resistance with current passing through which can explain fault clearing when cold but appearing after a few minutes .
Fuel pumps themselves can fail , or suffer corroded electrical connections due to their position under the back of the car , also worth changing fuel filter ( about £10 ) if it has not been done in a while .
Other than that , I'd wonder about a vacuum leak on the induction side of the engine , maybe a perished rubber coupling on a vacuum pipe somewhere ?
These problems can be tricky to trace , but usually are something fairly simple and cheap to fix .
Good luck .
