Requesting the assistance of the Oppo "brain" pool...

"RallyDarkstrike - Fan of 2-cyl FIATs, Eastern Bloc & Kei cars" (rallydarkstrike) 01/14/2018 at 09:43 • Filed to: Oppohelp

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Can’t remember if I posted this here or not, so asking again, haha!

I’ve noticed in cold weather that my 2009 Hyundai Accent hatch sometimes (it’s random) has a misfire when it first starts up until it warms up.

This usually only lasts for maybe 2-5 minutes and then it is fine, but it sometimes means I have to wait a few extra minutes until it settles before I can go to wherever it is I am headed. I haven’t pulled the codes when it does it in awhile but, if memory serves, it seems to be on cylinder 3 or 4 (I forget which, TBH) most of the time.

I’ve been told it can be condensation in the tank / lines from sitting in the cold temperatures, but it does it whether my gas tank is low or whether it’s full, so not sure on that one.

What does Oppo think? Could it be injectors failing...? Spark plugs...? Coil packs? I know the coil packs were all replaced a few years ago, so they are relatively new....not sure when the spark plugs were last done. The injectors are probably the original ones...

gmporschenut also a fan of hondas > RallyDarkstrike - Fan of 2-cyl FIATs, Eastern Bloc & Kei cars 01/14/2018 at 11:02

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a temp sensor could be failing, causing to run lean/rich.

i used to have that problem on my 914 where it would run lean. and  compounded with a vacumm leak that would randomly cause it to run super rich.

brianbrannon > RallyDarkstrike - Fan of 2-cyl FIATs, Eastern Bloc & Kei cars 01/14/2018 at 11:47

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Most likely carbon build up on intake valves or the valve adjustment is too tight

LOREM IPSUM > RallyDarkstrike - Fan of 2-cyl FIATs, Eastern Bloc & Kei cars 01/14/2018 at 12:11

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Intake manifold gaskets.

When they get old and hard they don’t seal well in the cold, allowing unmetered air into the engine which causes a rough idle and misfires. Once everything warms up the gaskets begin to seal well again and stop leaking (as much anyway) and the car runs fine until it’s stone cold again.

If you want to find the leak and don’t wajt to smoke test the top end, grab yourself a can of carb cleaner/brake cleaner/starting fluid/etc, or an unlit propane torch. Get the car running and spray the fluid around the top end (or open the propane valve without lighting the torch and direct the propane around the top end.) As you’re doing this, listen for changes in idle. When you find the leak the idle will either surge or the car will sputter even worse, depending on whether the fluid you’re spraying around is flammable or not. I prefer the unlit torch method, because you can easily piss away multiple cans of other stuff which is a waste of money.

RallyDarkstrike - Fan of 2-cyl FIATs, Eastern Bloc & Kei cars > brianbrannon 01/14/2018 at 12:54

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Carbon buildup, could be...but why would it run better once it warms up? Warming up doesn’t get rid of the deposits that would be there, would it?

I don’t know for sure, but I don’t think the valves have ever been adjusted, so I doubt they are too tight...if anything, after 135,000kms, wouldn’t they be too loose?

RallyDarkstrike - Fan of 2-cyl FIATs, Eastern Bloc & Kei cars > LOREM IPSUM 01/15/2018 at 16:32

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Hmm....might have to try this...I’ll try and do it when I get a chance!

brianbrannon > RallyDarkstrike - Fan of 2-cyl FIATs, Eastern Bloc & Kei cars 01/20/2018 at 12:19

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the carbon stops soaking up gasoline and valve clearances change as the engine warms up 

brianbrannon > RallyDarkstrike - Fan of 2-cyl FIATs, Eastern Bloc & Kei cars 01/21/2018 at 18:40

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Valve clearances also get tighter as they wear