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-   -   Cylinder 3 misfire (

PineyLGT805 04-09-2013 11:07 PM

Cylinder 3 misfire
Yes yes yes, i have searched and discovered tons of info about cylinder misfires.

My question is for the experts out there... '05 LGT is at the dealership trying to diagnose my misfire. Dealer has done everything they can without tearing the motor down to diagnose the problem i.e. swapping plugs, injectors, coil packs. Misfire stays on cylinder 3.

They performed a Leakdown test which revealed a 10% leak from cylinder 3. They now want to tear the motor down to discover why 3 keeps misfiring. Possible burnt valve they said or cylinder or i may even need a valve adjustment.

My purpose of posting this thread is to see what i should do. Should i pay to have them search for the problem or do i just drive it how it is or what? Registration is up soon and need it to get smogged as well, and it won't pass with the misfire... Thanks for the advice in advance

No power mods except catback exhaust and i drive it pretty tame ... 126,000 miles

xt2005bonbon 04-11-2013 03:56 PM

I basically got the same results as you but with cylinder #4. My engine is getting rebuilt as we speak. My problem was valve clearance.

xt2005bonbon 04-11-2013 03:58 PM

I think it is possible to check the valve clearance without pulling the engine. They 'just' have to take off the valve cover and measure it.

V8Bait 04-11-2013 04:03 PM

Have you checked the injectors? No fuel in one cylinder = misfire. Make sure the plug isn't faulty and/or the injector itself.

xt2005bonbon 04-11-2013 04:05 PM


Originally Posted by V8Bait (Post 4385850)
Have you checked the injectors? No fuel in one cylinder = misfire. Make sure the plug isn't faulty and/or the injector itself.

I think the OP mentioned that the dealer already checked for faulty injector/plug.

V8Bait 04-11-2013 04:08 PM


Originally Posted by xt2005bonbon (Post 4385852)
I think the OP mentioned that the dealer already checked for faulty injector/plug.

whoops now I see it :redface:

PineyLGT805 04-12-2013 11:08 PM


Got my car back today from the dealer. They replaced plugs, swapped coil packs and injectors and the misfire still stayed on cylinder #3.

They said my valve clearance's were good but still couldn't pinpoint what was causing the misfire.

So its come down to 2 options...

#1: I may be using bad fuel (i fill up at AMPM next to work, prob not the best idea) and the bad fuel and me pussy footing around could have caused carbon build up in the cylinder head not allowing it to close all the way and hence causing the misfire... Im doing a top end clean tomorrow and will hopefully burn out any build up over the weekend. My gut says this is a long shot, but hey! you never know lol

#2: is that I am close to burning out cylinder 3 and imma need to get it rebuilt. I can't see a car that is driven lightly and has only 126k miles could burn out a cylinder but like i said, you never know.

.... Ill keep you guys updated

xt2005bonbon 04-13-2013 04:31 PM

I hope it's not an ever so slightly cracked ringland on #3. How is your oil consumption?

1055 04-13-2013 05:25 PM

Could always try running some seafoam through it..

PineyLGT805 04-14-2013 11:29 PM

Well i did the Top End clean yesterday, drove around pretty hard to burn out any residue left over. Drives a lot smoother but still misfires. I may do another clean out next weekend and see but my gut is tellin me im probably gonna have to do a top end rebuild... bummer

PineyLGT805 04-14-2013 11:30 PM

... or is a rebuild overkill?

xt2005bonbon 04-15-2013 01:46 AM


Originally Posted by xt2005bonbon (Post 4388503)
How is your oil consumption?

^ This.

Have you seen this thread?

rob-2 04-15-2013 11:25 AM

I had a misfire in cyl 4 and did the following to resolve it:

1. Clean MAF
2. Moved coil pack 4th to 3.
3. Switched to better gas - running an oc booster to spike the bad gas up
4. Ran redline injector cleaner
5. Replaced PCV

Misfire has gone away completely.

I have a tone of blow by at stage 2 and need a catch can. Check your oil in the TMIC. If you have, this will cause lower oc burns due to the inclusion of oil.

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