Rough Idle / Misfire at Low Revs

[Haydo]

New Oxy sensors, thought it made a difference but after 15 mins running... still no joy. :rant: They did look shagged tho, esp. the passenger side - white **** on it (coolant maybe).

Swapped plugs around & leads 3 & 5 just incase they were dodgy even tho their new. Are "Hurricane" leads decent? Even chucked the new coil pack back on 3/6 to be sure. Took her for a burn & again when warm she starts popping & farting like before. Missing maybe knocking in top gear, didn't get on the highway, only had her up to 80. Checked plugs again, all good except #3 again but this time it smelt like it was oil fouled.
Just remembered, the old supercharger gasket was dripping with oil before replacing & looked like it had a section blown out from too much pressure or something, maybe related to #3 fouling?!?

Just for good measure, I replaced the purge hose cos the plastic rubber covered old one with rubber elbows was a bit sus.
Oh yeah, changed the injectors around too just to see if the plug fouling followed the injector - it didn't. Did a basic clean (not ultrasonic or pressurised) & replaced the O-rings too.

It's $h!tt!ng me up the wall. No time or $$$ at the mo & #uck!t it looks like I'm gunna have to replace the valve spring/lifter or something. Is there any good in car treatment that might help, like high viscosity oil treatment or "Gunk Valve medic" etc.??

One thing I havent checked it the CAS but with only #3 fouling it must be related to that cylinder yes!? Maybe chuck a hotter plug on #3?


Brett, you're a guru, any suggestions bro? Heaps of good karma in it for ya... maybe Carlton Draught too or :smoking: LoL.

Ordering OBD II scan tool from the U.S. I'm gunna need one I reckon.

 

[Haydo]

Two Words: Valve Spring

Funny thing is, when replacing the Intake Manifold gaskets i checked the springs on this bank & they seemed fine. Must have busted during road tests between changing/moving componenets around, but weak beforehand. Oh well, at least the mystery is solved.

 

[Brett_jjj]

Yeah, that'll definitely do it. At least you know whats going on with it now, which is always a good thing, a compression test would have picked that up, and that would have been the next step to take, as you had tried everything else with no success.. Let us know how you get on with it,cheers.

 

[Haydo]

Yeah, that'll definitely do it. At least you know whats going on with it now, which is always a good thing, a compression test would have picked that up, and that would have been the next step to take, as you had tried everything else with no success.. Let us know how you get on with it,cheers.

Brett, you're a bloody legend!

What shits me though is the mechanic said compression test was A-OK (see original post). Should have known, once you loose faith in someone you really have to question everything they ever said! So called "professionals" Meah, more like arse hats.

Need to buy a compression tester anyway, I was hoping to get one with a removable adaptor to plug in to my mates air compressor when we change over the spring.

Will keep y'all posted with results. After that, FIT pulley upgrade kit BWWWAAAAAHAHAHA!

 

[Haydo]

$30 in parts, valve spring & seal from Scotty @ Smiths Holden & Black Betty is purring like a kitten again. WOOHOO!!
:driving::drink:

It was the exhaust valve spring which explains the popping/farting from exhaust when she was warm & rough idle too.

Thanks to everyone for their advice!
Changed a few parts I didn't need too but still far cheaper than handing over hard earned coin to a scamming "mechanic" & educational fun at the same time.

Kudos to Brett, the intake manifold gasket had to be done...
& (maybe) the subsequent coolant leak stuffed the LHS oxy sensor, thanks Dave.

Took some time but cost a helluva lot less than the $1500 minimum I was quoted by Ultra Toss Motors Geelong West.

A little hint, if ya need to change a valve spring & don't have an air compressor or the spark plug hole adaptor to suit it:
Replace the plastic purge hose with a $5 rubber hose from Repco, move the problem cylinder to TDC by moving the crank - if you remove all spark plugs you can do this fairly easliy just using the serpentine belt - then use said dodgy purge hose to make sure you don't drop the valve by putting it in the spark plug hole... kills 2 birds with 1 stone.

 

[som]

That would have to be one of the best threads I've read on this forum.I'll bet that many people,like me ,may not have felt that they had anything constructive to add as we've followed the thread but at the end of the day you had the right result. And.....let all of the members know that your car is sorted. Too often someone will post a thread,gets lots of help but then not bother posting the end result.Good on you guys.

 

[Haydo]

That would have to be one of the best threads I've read on this forum.I'll bet that many people,like me ,may not have felt that they had anything constructive to add as we've followed the thread but at the end of the day you had the right result. And.....let all of the members know that your car is sorted. Too often someone will post a thread,gets lots of help but then not bother posting the end result.Good on you guys.

Ya know what Som, I reckon you're on to something here... So what do we do about it?

Ask the same unanswered questions, like "Where the #uck is the EGR valve/cooler on an L67 cos I can't find it!?"

Meah, whatever. My mum brought me up well, so I believe it's just good manners to finish what you start.

Told ya's I'd see this one through :spot on:

Thanks for the feedback dude :beer chug:

 

[Haydo]

#uck, cars do my head in, Just like the ladies... but I love gettin' inside & givin' it to 'em both when they're ride worthy!

Anywho, Like I said above Betty is purring like a kitten since replacing the dodgy valve spring (& LIM & other stuff etc.) However, since then I've had the odd overheating problem. First time it happened I thought, "########, you didn't bleed it!". Did that & all seemed to be well for like a month or so but bugger me, lately after say 10 mins highway driving, I get the overheat warning again. Pull over quick & notice steam coming from under the plastic cover/shroud on top of the radiator. Also noticed the drivers side thermo fan wasn't spinning. Swapped a couple of relays (high beam with high speed fan from memory). Seemed OK. Thought I need a new fan relay. Still, happened again a few weeks later. Added about 2LT to the cooling system. Again seemed OK for a couple days then same again but more steam from under top radiator cover. There was the odd occasion when sometimes overheat warning would sound but then temp would drop quickly before hitting "H" & sit at about half.
I had been meaning to flush the system since doing the work above but this latest $h!t prompted me to take action & do it. Got a bit of crap out of her but seemed pretty good/clean.
I'm tippin' the radiator has a leak somewhere in the centre but until I pull it out completely & check it out I can't be sure. Ergo, I have a couple of questions for the wise folk on this fully sick webiste:
- Thermofans: Should both fans operate simultaneously? Drivers side is suspect (sometimes spins). High Speed/Low Speed fan relays?
- L67 SCV6: Fussy with Coolant? I've been a bit cheap using water until flushing/refilling properly... want to fix everything cooling before wasting $$$.
- Thermostat: Replaced with cooler Mace part when changing LIM & Supercharger gaskets, does it need rubber seal (like old one had, I think) or is just gasket OK?
- Any tips to hook a brother up?

 

[Vlad01]

could be a faulty thermostat, have it happen to me twice, was faulty from new.

the temp would surge all the time and occasionally overheat. got another new one and never a problem again even years latter.

 

[Haydo]

could be a faulty thermostat, have it happen to me twice, was faulty from new.

the temp would surge all the time and occasionally overheat. got another new one and never a problem again even years latter.

Maybe... tho after bleeding she was all good, until a few days ago... just got a replacement heater valve today cos it's spewing coolant like a mofo... airlocks in the SCV6 are a PITA!