Rough Idle / Misfire at Low Revs

[Haydo]

G'day Brett,
thanks for the reply Bro. I'm goin' nuts & the specific info helps me refrain from psychosis. ;-)

Blown gasket not show up on a vac test?

OK, so if I change the inlet manifold gasket I may as well do the thermostat & it's gasket then flush the cooling system at the same time yeah?

 

[Brett_jjj]

Yeah, definitely replace the thermostat and flush the system including the heater core at the same time.. A cooling system pressure test will show up most leaks in the cooling system, but sometimes these gaskets wont start to leak until the engines gets up to operating temp, so these tests can sometimes fail to detect all leaking/weeping gaskets. If the engine has done over 200,000km, then you can pretty much guarantee that the inlet manifold gaskets will be stuffed and leaking ..

 

[Haydo]

Well, at 191000 KM even if it's not shagged it may as well be done... might go a cooler thermostat at the same time.

Inlet Manifold Gaskets - Mace Engineering Group

For another $22, may as well do the Supercharger Gasket at the same time ya reckon?

I REALLY appreciate your input. Thanks man!

 

[david dubbo]

my gen 3 was playing up a bit at idle and after changing everything and not finding a problem I changed the o2 sensors idles perfect again although the o2 sensors where obviosly buggered it did not show up doing a fault check so might also be worth considering

 

[Haydo]

OK, new Gaskets fitted & manifold back where it should be...
Supercharger will have to wait until tomorrow. Speaking of, there was a $h!t load of oil all over the manifold when the charger was removed & the charger gasket was FUBAR. Lucky I got a new charger gasket with the manifold gaskets. Is there supposed to be oil everywhere when the charger is removed?

Also found a vacuum hose that looks like it's been cut. WTF!? (see pics, 1st pic cut hose joins to elbow on right hand side, 2nd pic of cut end)

Need to pick up a few parts in the morning to finish the job tomorrow: supercharger oil (haven't checked it's level yet), gasket for the new thermostat & U bend hose for it's housing, a few O-Rings for the heater pipes which were a bitch to remove, stupid tensioner pulley assembly.

Anyone happen to know the torque spec for supercharger bolts?
Edit: Nevermind, step 1 approx 17Nm step 2 21-27 Nm

 

[Haydo]

Job Done. One of the manifold gaskets was definately shagged & neither looked too good. Seems to run much better, still a bit rough but haven't driven far yet so maybe the computer hasn't re-learnt...

Still getting popping from the exhaust when she's warmed up.

Need to sort out this cut host & maybe some O2 sensors like Dave suggested.

EDIT: Looks like the Boost Control hose between the Actuator & Soleniod. I'll have to remove the actuator & check it out...

The acutator had been broken at some stage & previous owner tried to glue the port back to the module. Managed to ream the socket & repair it OK. the vacuum hose (more like a straw) is attached now & all good.

The tensioner assembly is tweeting/squeeking & jumping up & down a bit, seems to be in time to the misfire/stutter.
I'm picking up a new one Thursday, maybe O2 sensors at the same time..

STILL IDLING ROUGH - I'M GOING INSANE! PLEASE HELP - ANY IDEAS APPRECIATED!

 

[Haydo]

Is there an EGR Valve on the L67?
If so, I can't find it!!

 

[Haydo]

Well, getting back to basics...
#3 spark plug is fuel fouled & the injector seems to be making a different sound to the others on the same bank. ECU making it use more fuel? Why for?
Given the exhaust popping noise when warm I'm leaning to the O2 sensor like Dave said. Does that sound fair?

 

[david dubbo]

yeah I couldnt work out why mine was idling so rough there was no faults logged and a mate of mine was saying o2 sensors I didnt believe him as I thought if it was surely it would log a fault. I would still be chasing the problem but he went and bought me some new sensors we put them in and almost instantly it was perfect so I paid him back for the sensors and bought a carton and we drank

 

[d.k.vmatt]

if you replace the coils get ones for a supercharged car as they are sligtly better and throw a more powerful spark and will bolt straight up to a normal car.