Vacuum leak or not?

**soop** · 02-07-2011, 02:52 PM

Hi guy's.
I've had an issue for a number of months now with my LS1 misfiring and wanting to stall.
Crusing at 100km/h (60mph) its fine, but when it comes back to idle it misses and carries on, as if the idle is too low. It has alot of trouble taking off and can go very close to stalling (on occasion it has).

So far I've replaced;
Spark plugs.
Ignition leads.
coil packs.
MAF.
IAT.
O2 sensors.

I've checked it with my scan tool and there are no codes. I've had o2 codes come up from time to time but I'm thinking thats due to the problem not causing it as Its happened with the old o2's and brand new items. The Long term and short term fuel trims are all normal as well.

**98maro** · 02-07-2011, 03:42 PM

I would change the air filter. And clean the MAF. but if I'm wrong u said u replaced it?
Sounds like a vacuum leak. But if u notice a drop on gas milealge. Abd heard some air coming out of somewhere on the engine bay. Then you have a vacuum leak.

When was the last time you replaced your gas filter?

**soop** · 02-07-2011, 04:22 PM

Ah sorry, I've replaced the fual and air filter as well.
I can't hear any sucking sounds from the engine bay. Nothing obvious anyway.

Although there is a "Psttuuuu" sound once I turn it off. I had the manifold off to replace the oil pressure switch, but I'm damned sure I put it back correctly. Although I've been tempted to remove it again and repeat the process.

**98maro** · 02-07-2011, 04:53 PM

What year is your car ? Does it have EGR?
mime was doin that and I had to remove the EGR tube from the intake and didn't put it back right it was makin some sucking noise,
If your engine has egr you should check that.

**soop** · 02-07-2011, 04:55 PM

Its a 2003 model.
I'm not sure about the ERG. I'll look it up but I don't think it has the ERG.

**98maro** · 02-07-2011, 05:00 PM

Probably dnt have it.
Damn idk what the problem could be.
I hope some 1 else can help you out.

**soop** · 02-07-2011, 05:01 PM

No worries mate, it has just about everyone stumped I think.

**soop** · 02-07-2011, 10:49 PM

I just pulled the throttle body off, and everything in the intake reaks of fuel, even the intake pipe running from the air box to the throttle body.

Strange!

**soop** · 02-07-2011, 11:56 PM

Never mind, Car answered the question for me. Cat melted. I gave it a big rev while I was standing next to it this arvo and it blew a massive chunk of catalyst out of the rear end!