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Vy ss running rough

Wagon92

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Hey Guys, I have a 2002 VY SS and has been running great the past 3 years iv had it, all of a sudden its started running really rough to the point it stalls trying to idle. I think its a bit of a coincidence that it happened after I filled up the other day.

Any way seen that it happened after I put pretty much put a full tank of fuel in I was thinking it was a fuel issue, but I have checked for fuel pressure and seems to be plenty there, and also changed the fuel filter even though it was only 6 months old just to make sure. there was no water or contamination in the fuel so I believe its nothing to do with the fuel I put in (Was Shell 98)

I have found sometimes when I start it, it runs fine, and then if I give it throttle to about 3000+ rpm it seems to go out of time and then when I try to bring it back to idle it wants to stall, and I have to leave it for a bit so that it starts up normal again. I have disconnected each coil pack and also injectors and not one really made a difference to how it was running, at one stage I had the front 4 disconnected at once and it was still running the same :hmmm:

Just for extra info it is obviously an LS1, MAFless Tuned with an Ramjet OTR (had this for at least 2 years with no problems), Pacemaker 4into1 headers, std cats, Manta 2.5 catback, other than that stock engine wise.

Plugs, Leads, fuel filter, are all pretty new, any one got any ideas? will try get a video tonight
 
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Wagon92

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Hey Guys, I ended up changing my plugs and leads kind of just because it was due for it but still with no fix and didn't want to just start spending money on sensors and new vac lines and then possible still not have the problem solved so eventually took it for a 40 min drive on a flatbed to an auto sparky and they found nothing so they look it down to a Mechanic and they suspected a broken inlet valve spring, turns out they were spot on and the inlet valve spring on cylinder #4 had snapped at the top, so it was still sealing at low revs and then not at higher and wouldn't seal again. Very surprised there was no tapping or anything though, just a very slight noise in the intake manifold.

very lucky the valve didn't hit the piston!!

DSC_0140.JPG

Regards,
Wagon
 

Tonner Matt

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