vs idles great, runs like crap

[macka75]

hi all,

i searched the forum but couldnt find any matching this exact problem..

just replaced CAS with genuine one. car started great, idled smooth instantly, but a touch of the throttle and it had a miss bad. thought it was just cause it was cold sitting for a few days. took it for a drive and it ran like a pig, NO decent acceleration could be achieved as it was missing so bad. if held at 2-3000 rpm idleing it runs fine.

did a code check and it just gave me constant 12's so all good there.

all i have done is replace the CAS and power cable from battery to starter. is there a wire i could have upset during the mighty task of getting to the harness that holds that wire. had a look but bit vauge on wiring.

[88GreenVN]

Have you mixed up the leads? How old are the plugs/leads?

[Brett_jjj]

Id be testing the 3 coils,I have seen them test ok on a multimeter but still cause a miss.So dont test them that way.Get a known good coil and try it in the 3 places one at a time where yours go.Sometimes these coils break down under load --(idle ok but miss when under power).The numbers on them dont matter ,they are all the same coils and they can go in any of the 3 places.The new ones you buy dont have these numbers ,the ones with numbers have usually been on the car since new.They slowly break down over time too.I had a coil stuff up,I replaced it with another second hand one.It fixed the problem and it was running good again,then I bought 3 new coils from holden the following week and I couldnt believe the difference in the starting,running,power and the fuel economy,it all improved out of sight.If Id known they made that much difference I would have replaced them ages before,even though they were still running ok.As I said before they must slowly get worse over time.So now I recommend replacing all 3 at the same time.Try to buy MSD or genuine holden ones.Usually a faulty coil wont throw up an error code either.

[macka75]

thanks for the replies.about to go out and check the plugs. i just unplugged each lead from coils, plugged them back in and it ran great for 5 mins then back to the missing and backfiring under bonnet as well when under load.

seems strange that is ran ok for a short time

[Brett_jjj]

It might be a bad plug lead, silicone type leads only have to be kinked or pulled to hard when unplugging them from the plugs or coils and it breaks the core inside the lead which renders them pretty much useless.. If new plugs or leads dont fix it,try testing the coils like Ive already explained how to do.The voltages these newer cars run through the ignition systems wears out plug leads fairly quickly.Unlike old points systems where leads would last for years.