Hi Guys, I own a 4x4 sierra cossie with a stage 1 setup (280 Bhp) just had the car (supposedly) setup at the local garage.but it's not right.....
when the car is idling it revs up itself to 2000Rpm then it will settle down for a few minutes then start again,also when feathering the throttle when pulling away it also splutters.when accelerating hard it misfires from 4-6000 Rpm and i also get quite a bit of black smoke when you plant the throttle after over-run. Just had a new phase sensor fitted and the problem is still there !!!!!.
Any ideas anybody as this is doing my swede in!!!....38 miles on a tenner!!!!

 

could be a number of things m8,I would check the Iscv(as you say it's hunting on idle) or the blue temp switch @ rear of passenger side of head(as it's kicking out alot of black smoke) to see if they are working correctly! also what plugs are you using(maybe breaking down under load)

 

Hi mate,the ISCV has been cleaned out and all is ok with that,have got my suspicions on the coolant temp sensor,i think it could be that,as i've never changed that,looks a bugger to take out aswell,being right underneath the manifold

 

oh forgot to say that the plugs are c59's !!!! cheers