misfire when under boost ?

[craigtd]

can anyone help me ? my 406 2.0 turbo 8 valve petrol has a misfire when its under boost, has anyone come accross this before

when im driving without boost it somtimes misfires aswell help help help please.

[herefordbilly]

Mine was fuel pump.

Have you turned up the boost or changed your normal fuel garage?(Tesco petrol is terrible )

Could be simple like fuel filter,plugs,leads try that first then check pump .

[craigtd]

why would the fuel pump make it misfire

[herefordbilly]

lack of fuel.

[craigtd]

no its not that, ive been looking on the web and on other makes of cars its mostly down to the spark plugs been to hot and the gap been to big, so from what ive seen i need a colder running plug with a 0.8mm gap so the boost wont blow the spark out.

[lozz]

Its all Guesswork mate,
just coz some post off the net makes you think it needs better plugs dont take that for granted,


when was the car last serviced?

is the car missfiring from cold or is it hapening mostly once the cars been run /got up to temp,

take a plug out and have a look what colour they are you will be able to tell off the colour if theyre down or if shes running rich.

[craigtd]

ive not had the car that long but it did have a full engine rebuild about 29000 miles ago, inc, head,pistons,turbo,crank. the man spent alot on it so i think it would of got everything it needed then,i was just going to start with the cheepest and work my way up lol. it could also be a lambda sensor as they give the same symptoms when they go wrong.

[craigtd]

getting a set of plugs and leads at the weekend and i will be setting the plug gap to 0.28 to see if it helps any, i will let you know how i get on after its done.

[craigtd]

been onto turbo technics today and they say it is a sensor giving me this problem and to get a code read,so im getting that done on saturday before i spend any cash on it.

[craigtd]

had the code read done the day and the only code that came up was the boost control valve,so i done a vacuum test on the actuator and it held the vacuum well so it has to be the control valve

[craigtd]

well i have sorted my boost problem and misfire out to day, the actuator was set wrong so the waste gate was open a little bit all the time,i set it today and took it for a run and its like a differant car,all i need now is some colder plugs so they can cope with the 0.8bar its running im going to get it on a rolling road once i put the new cat back 4inch system on, i think it will be around the 210bhp mark