FLASH1970

Ok, so I've been having this problem with my car since I bought it 40K miles ago... I bought it at about 36K miles, with a certified warranty. I start it up, and within seconds the CEL comes on. It only does it maybe once every few weeks. I don't notice any performance loss while driving it. I recently tried changing plugs, didn't help. So I swapped coil packs around, seafoamed it, and still no luck. It did change cylinders this time. But, I swapped the two left coils, and the 2 right coils. Usually the misfire occurs on cylinder 2. This time it was 3. A couple times it has been 3 as well in the past. I was hoping the misfire would follow the coil so I could narrow it down, but no dice. So, do you people have any ideas?

Dealer rant part...
The really aggravating part is the car came with a certified warranty when I bought it with 36K on it as I said before. Every time I brought it in they'd clear the code and send me on my way and tell me if it happens again, they'll look at it. After a few times of this happening, I told them I was sick of being fed the same line and wanted to schedule an appointment to have it serviced while it was under warranty. They said unless it does it while they have the car they can't do anything, sorry. Now that it's out of warranty, they want me to bring so they can look at and charge me for it... needless to say I'm not happy. Dealer tested the coils which checked out, then wanted to put GM plugs in it because according to them, the plugs the car came with were specifically designed for that car and the Autolites I put in are no good... yeah, right. I told him the misfire was occurring on the same cylinder with GM plugs in it too. They also wanted to clean the injectors and put new coil boots on it. I don't think it's the coil boots because the misfire would follow that boot if the boot was bad. They wanted 300 to do this, also wanted 100 for their diagnosis. If it didn't fix the issue, I'd be out the money they said. They'd also want to look at the car again for further diagnosis if the misfire continued, charging me more money...

714ionredline

iTrader: (1)

Yup I have the same issue im wondering if its time for a valve clean up. But I remember that some member did a valve clean up write up to try to fix the misfire code and it still didn't help.

LNFTX

Valve gunk is a good place look on a higher mile lnf you can pull off the mani pretty quick yourself and verify how bad it really is
Also could you try another dealership for help your car would have came with a 5 year 100,000 mile powertrain warranty regardless of the certified warranty or who originally bought it

umrdyldo

iTrader: (1)

Let's clear some things up. The dealer is actually right about plugs. Stock plugs stock gap is your best check. Almost any person and vendor will say the same. So put stock in.

Can you monitor misfires to see how many you are getting? I use Torque app on phone. Many ways to do this.

Many people have reported just replacing just replacing the boot portion of the coils. Something like 5 bucks at auto zone.

Seafoam doesn't help. Don't waste the money. It won't remove valve gunk. I would get a USB inspection camera and visually inspect the valves for gunk. I'm guessing this is your issue.

Last but not least. How is your battery? This issue arising on weak batteries. Has happened to dozens.

If you can prove valve gunk is heavy then the dealer needs to fix it. Especially if you brought it up before 5 year warranty. If you need help there is customer service rep on here to help.

thedubsack85

Sea foam does in fact work if done properly.

If it was valve gunk the missfire would not jump when coils are swapped it would stay in the cylinder that has build up..Im thinking you didnt do the sea foam correctly if there is still build up after the treatment.


Valve gunk build up would be on the owner not taking proper care of his car not the dealer.


Start with inspecting all ignition components for anything that would make it not have proper contact. Plugs,boots,coils and such. then check for proper fueling blown injector seals but the dealer is right unless they can replicate it the issue with the car in there possession they dont have to pay to throw parts/labor at it if they so choose some dealers are nice alot are not sadly

ECaulk

iTrader: (6)

No, Seafoam does no work on an LNF injectors are in the cylinder chamber and seafoam is not a strong enough solvent to remove coked intake runner valves.

Also go buy some new plugs they're like $35 at Advanced, get the AC Delco plugs. That could correct the issue, i'm assuming you're still on the stock tune?

ae_xiong

iTrader: (3)

In the same shoes. Only misfires when it's at WOT though. Also, usually happens only when shifting from 1st to second. Then when I NLS from 2nd to 3rd and 3rd to 4th it's perfectly fine. Just back fires kinda loud and blew one of my MAP sensors. LOL This happened before and I changed the spark plugs as they were beyond burnt and it fixed the issue for a few months. Now issue is starting to return. Gap is at 0.035(all 4) I believe with Trifecta tune and full bolt-ons at 23PSI. Planning to use seafoam n change oil.

rnjmur

I agree with above, many people have had issues with misfires when using any plugs except the stock NGK plugs. I would put the stock NGK plugs (ILTR5D) or AC Delcos in and see if that helps.

FLASH1970

Thanks for the responses peeps. Car still has stock tune. It does have a K&N SRI on it now, but for a couple years it had the stock airbox on it and misfired just as much. When i seafoamed it i watched the video and put some through the IM by letting the vaccum line sip it up. Also put some in the gas tank. Got a little smoke out the tail pipe but not much. I got the car with about 36k on it and its been doing it since i got the car. Wouldnt think thered be gunk build up on the valves at 36K. It had stock plugs in it and it misfired. so, I dont think its the plugs. I do have a borescope so maybe ill pull the IM and take a.look. yeah, it has the powertrain warranty but the dealer told me that wouldnt cover the boots, plugs, cleaning, diagnosing. So, the powertrain warranty is about as useful as the certified one unfortunately. Also, im pretty sure the battery is good. We've had a lot of negative temp weather here in WI this year and its always started. The misfire usually happens on start up or with 10-15 seconds afterwards according to the umpteen times the dealer has scanned and cleared the code. Only once it stumbled and misfired while driving and that was a couple years ago. Ill try seeing whats up with that 'torque' app. Thanks again everyone.

ECaulk

iTrader: (6)

If it misfires when cold or starts a little harder in the cold its your plugs. Powell has a thread around here about LNF valve gunk and how to drive to help prevent the build up. Plugs are a cheap replacement and if its over 50k its worth changing the plugs

Wired

iTrader: (3)

I'm the one who had start up misfires and WOT ones. After doing a valve cleaning by hand the startup misfires went away. The odd stumble on start up occasionally did not.

My car was at 30k miles and there was plenty of gunk built up. Don't take your intake manifold off, just remove your brake vacuum line and insert the bore scope through there.

https://www.cobaltss.net/forums/how-...88/index4.html

bmartz1991

iTrader: (35)

That was at only 30k miles? Damn...

FLASH1970

my bore scope isnt much smaller than a spark plug hole so i think ill have to pull the intake manifold. ill check your link when i get home. im at the dealer again to get the code cleared. I was just here yesterday for the same reason.

to the person that suggested plugs, i just changed them.