Vectra 2.6 missfire under load

[scottieg]

hi my vectra 2.6 gsi has a horrible missfire, recently serviced been fine for a couple of weeks had a problem with the key been recognised in the ignition which was imobolising the car. got that sorted and on the way home opend the taps up and it started missfiring stunk of fuel in the car turned ignition off then on while driving i regain a normal running order until you put your foot down again something is failing under load i have had it diagnosed the mis fires were on 5 and 3 so initial thought was coil pack but just changed that and there is no difference aarrhhhh my next thoughts are crank or cam sensor. or maybe inlet manifold gasket. what you think????

[Andy^mk3]

Were the plugs changed on the service?

Sounds like you may have a poor spark which is showing up under load

[scottieg]

yes all plugs changed I put ngk 1's in

[Paul]

Did you not change the inlet manifold gasket then?

ECU light will be on, so a good fault code reader will confirm what cylinder is missfiring

[scottieg]

i didnt no, since then it has had tech 2 diagnostics and came up with multiple random miss fires i have now changed all 6 plugs both coil packs, i have checked vacuum pipes, you can rev the engine on the spot and no miss fire but as soon as you drive it and go above 3k with more than 30% throttle the miss fire kicks in turn ignition off then on and its reset, i am now thinking like you say inlet gasket but it has been about 2 months now since i removed it or something that touches everything like contaminated fuel, what else could make every cylinder miss fire under load????

[scottieg]

eml bulb has blown it used to come on before you start and now doesnt can only assume the bulb has gone

[Andy^mk3]

Could be an ECU fault. Had a 1.8 (XE1) Vectra in at work last year with a misfire under load, all the usual suspects were tested and changed with no difference. Eventually found that the ECU signal was faulty which was found using a scope, the ECU was sent for repair and it was perfect again. Whether that engine uses the same ignition system I don't know, but it's another idea at least.

[Paul]

XE1 ecu is toss

[scottieg]

would of thought so, now thinking do they have a small inline fuel filter, if that gets bloked restircting the fuel could it cause the car to go into limpo mode and misfire until reset and correct fuel pressure is achieved??

[scottieg]

car is fixed small vaccuum pipe from throttle body to ??? was trapped restricting proper vaccuum presure every time the plenums opened simples and a dirty crank sensor was the coarse of an intermittent starting problem everything changed small tarty jobs now getting ready for billing