[markmustang1]

Hi if a car when revved and turned off,runs on a bit is this caused by ignition being too far advanced?cheers mark

 

[mygasser]

firstly you should never rev the engine and immediately switch off. sounds good but the press of the throttle puts petrol in the bores that then doesn't get burnt 'cos the ignition is off so no spark. the fuel washes oil off the bores so on restart the rings aren't lubed properly. lecture over :lol:.
so to the running on, how old is the engine? i mean how long since it was built/rebuilt not the year? it may have carbon build up on the valves, pistons and combustion chamber which will get hot enough to burn any fuel present after you switch off. this is made worse if you rev then switch off. you should know if it's too far advanced as the engine will be hard to turn over and may try to 'kick back' on the starter as the piston tries to fire. the plugs stop firing once you switch off so shouldn't affect running on anyway.
lastly does the car run on if you just switch off without revving first? if so i'd be inclined to go with carbon build up.

 

[buick350]

all of the above, idle too fast?

 

[markmustang1]

Hi thanks for the reply.engine is rebuilt 2k miles,only does it if rev a bit then turn off,if you dont rev it its fine,car runs good,not hard to turn over etc.cheers mark

 

[mygasser]

you know the answer then, don't rev it before you switch off :shake::lol:

 

[kapri]

Depends what you mean by running a normal sounding engine that stops normally just NOT as soon as you switch it off or a juddery engine that makes a whooshing rattling sound before it stops.

Think this links in with Nobodys thread re running on as well ? Alternator feeding the ignition still ?

 

[mygasser]

but it doesn't do it if it's not revved first kev. strange.

 

[chrisvs]

but it doesn't do it if it's not revved first kev. strange.

Is it possible that it's dieseling on the extra fuel that's squirted in before killing the ignition?

 

[mygasser]

if it's a recent build there should be no hot carbon to ignite the extra fuel.

 

[buick350]

If it is a holley and transition slot too exposed can cause this, too much air and fuel getting I after shutdown