CDTI 150 Dreaded flat spot HELP!!!

[keets]

Hi,

Started with a flat spot around 1800rpm had tech 2 plugged in which shows EGR valve/MAF sensor. Cleaned the EGR valve hoping this would cure, it didnt. I unplugged the EGR valve and took it for a drive and the flat spot had gone. So I obviously presumed I needed a new EGR valve. Bought one fitted it and guess what, the flat spot automatically came back. I then fitted a air flow sensor which made no difference. Ive subsequently fitted the fiat blanking plate which helped the problem for a while. The car now seems to be getting worse again.

Could anyone suggest something to try as im struggling. I cant understand how the misfire is helped by blanking the EGR when fitting a new one only makes it 10 times worse.

P.S Ive cleaned boost sensor.

[Dan_BlackSRi]

Best way, totally blank the EGR valve (using a full blanking plate, not the Fiat gaskets) this way you will know for sure if its the EGR valve or not (with new one it could still not be sealing correctly).

[keets]

Ive blanked it off completely and although it considerably helps the misfire still happens.

[AntSSSS]

Is your swirl bar still attached and moving?

3rd Injector plug mod done?

[Dan_BlackSRi]

Is your swirl bar still attached and moving?

3rd Injector plug mod done?

Thats the next thing.... what year Vectra is it..?

[keets]

Its a 2004 '54'

Swirl valve is still attached and Ive watched it working.

Ive not done the 3rd injector mod as I cant see the connection between that and the EGR valve. My point being when the EGR valve isnt blanked off it runs like a dog whereas when its blanked it improves but doesn't completely cure the problem. I may be wrong but cant see how the 3rd injector mod could be connected to this.

Ive took the pipe off the the throttle body and that seems to be clean, im tempted to take the throttle body off to check the soldering in the PCB.

[plasma]

A decent remap will remove all flat spots

[keets]

This is more of a hesitation/ jerk similar to when your running out of fuel than a flat spot

[RocketDog]

I have a very similar problem. So far I've changed the MAF and MAP sensors.

MAF was knackerd so the car wouldn't breathe properly, I thought the MAP was also knackerd but after a swap out this wasn't the cause for me.

Also tried swapping the boost control vavle but this too isn't the cause.

My EGR looks pretty new but I didn't fit it, I've also cleaned it and the throttle body out, but still no joy.

I've yet to change the vacuum pipes, fix up the 3rd injector mod or check the swirl flaps in more detail, but again the swirl flaps I thought were OK but I'm being advised that the swirl bar should move smoothly and not hesisiate as it does under deceleration of the engine... I thought this was due to the change in pressure as the engine slows down but perhaps not. Could just be carbon build up.

I'm sorry that the above isn't really fix, but I thought I would share so perhaps it saves you buying components that you probably dont need.

[Dan_BlackSRi]

....cant see how the 3rd injector mod could be connected to this.

Maybe you have two faults.....