VY SS running rough.

[faBReGaS]

hey guys.. I recently had an exhaust fitted to the SS. it started running rough.. Orgininally i thought it was the o2 sensors or it had just been thrown out of tune. I took my car to GM Motorsport to get in mafless tuned, and they said they would pick up on their computer if the o2 sensors were gone. It came up all clear and they carried out the tune. When i got the car back it was running wonderfully! Its now been 2 weeks since i've had the tune done and the car has started running rough again.. it feels exactly the same as when it first started running rough. It gets a bit shaky when im slowing down and when i come to a complete stop. When i drive its normal. i have no idea what it could be except for maybe the leads or spark plugs.. but then again it would be running rough while driving at normal speed if it was that! anyway im lost.. anyone have any ideas?

[faBReGaS]

Bump guys.. Still need suggestions! I'm thinking about giving the throttle body a clean?

[monaro327]

if it runs rough when braking might be a vacuum issue?

[Benboy]

More details required as to ALL engine modifications.

[faBReGaS]

The only mods ive done to the engine car is a Mafless tune, ramjet OTRCAI, twin 2.5" exhaust with pacemaker tri-y headers. it had all of the bolt ons before it was tuned, and since having it tuned it has had nothing removed or added. I thought it might of been the tune itself but it was running fine for a week after the tune? Im changing my fuel filter tomorrow, but dont think its a problem with fuel flow. anyway any ideas will be much appreciated.

Cheers guys.

[Kingston_99]

what sort of fuel are you putting in her? these motors dont like normal unleaded. they love Premium Unleaded, i made the mistake of putting in normal unleaded once (lucky i only put in 5 liters). but yeah i had the same problem, engine would run rough time to time. so as soon the tank was empty i put some premium unleaded and she was back to normal.

[faBReGaS]

Only petrol that has ever gone into my car for the year and a half of owning it is BP ultimate 98.. Never use anything else except once I filled with shell v power 98 which I wasn't happy with so went back to BP Ultimate. This has really got me frustrated now.. I might get some good ignition leads and spark plugs next week pay day n see how I go .. Any other suggestions are greatly appreciated boys keep em coming because I have no idea!

[ARATIC]

Check the hose which runs from the throttle body and goes around to the back of the drivers side head, these can crack causing a vac leak and idling problems. Also check the rubber hoses which run into the firewall (cant remember where they go from atm)

I wouldnt do the leads yet - if there were a problem with the leads GMM wouldve found it when on the dyno. The amount of ppl who buy new leads and find theyre not the problem is crazy.