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Random stumble on startup after sitting for a few days

11K views 19 replies 8 participants last post by  seantoomey38 
#1 ·
Twice now when I have not driven my E for a few days (both times it was fairly cold and humid), I started it up and it stumbled and had a rough idle for a few seconds, then it cleared up after about 30 seconds and ran fine.

Car has 103k miles, plugs are brand new (maybe 1000 miles) on NGK Laser Iridium (OEM plugs). Car gets top tier fuel, MMO added to gas, regular treatment from Techron every 5000 miles, and has an oil catch can (which doesn't catch as much as our 2005 Accord's catch can or 2006 Sienna).

Any ideas?
 
#3 ·
Is it possible,the gas is bleeding back from the injectors. I had this problem a few times. Each time it happened, I had just put the key in and immediately cranked the engine. Since then I've left the key in the ON position for a few seconds(to give the fuel pump a bit, to start the gas flowing) . I haven't had the problem since.
 
#6 ·
This is very possible. I don't have a key, so I just get in and mash the button. Never giving the fuel pump any time to prime. It only happens when the car has been sitting for a few days.

WAG moisture getting into coils. Have you scanned for any codes ?

If it sits inside a garage for two days does it do the same thing, less condensation opportunity.

Sounds funny but before starting run a hair dryer for 2-3 minutes over top of engine where coils are, then try starting car.
I have a Scangauge 2 hooked up at all times, no codes. I assumed some sort of moisture issue, didn't think about coils. Might be time for new ones? Or just the seals?

My Accent did this. New battery fixed it right up. In my case, the radio was also killing the battery if I left it on while I was cleaning the car or working on it. It also gave me a series of 0300 codes and lit the MIL.
The battery is 2 months old.
 
#4 ·
WAG moisture getting into coils. Have you scanned for any codes ?

If it sits inside a garage for two days does it do the same thing, less condensation opportunity.

Sounds funny but before starting run a hair dryer for 2-3 minutes over top of engine where coils are, then try starting car.
 
#5 ·
My Accent did this. New battery fixed it right up. In my case, the radio was also killing the battery if I left it on while I was cleaning the car or working on it. It also gave me a series of 0300 codes and lit the MIL.
 
#12 ·
Flooding? With gas? Or a moisture/condensation issue?

(Unlucky '13) Hyundai Elantra GT 6-Speed Manual

She's problematic; a new problem every month. Yet, I still love her. She will be mine until 200,000 miles. Love and marriage hurts. She's my Lady Unlucky '13
Don't call her unlucky, or she will be! Mine has been rock solid. What notable issues have you had every month? Just curious.
 
#16 · (Edited)
Intake valve deposits is what it is, plus buildup on/in the injectors. What happens is, after the engine is nice and cold throughout, as it is when it sits overnight, you go to start it up and the car calls for a rich mixture. So lots of fuel is coming out of the injectors. Problem is all the carbon and blow-by gases over the years have built up on the intake valves. These deposits act like sponges, especially after several hours of not being in use. You go to start it up and it calls for a richer mixture, and the valves end up absorbing a lot of the fuel that the ECU is expecting the engine to burn. So it starts stumbling because it is not getting the metered fuel it is supposed to be getting. After a bit of running, the intake valve deposits will become saturated and not absorb any more and the car will run fine. That is, until the next time you let it sit for hours and give those deposits time to dry up again. The answer is BG44K. That stuff works. One can works for 20 gallons of fuel. If you have sticky injectors or suspect clogged injectors, you will feel it work minutes after putting it in. Brother's truck had a misfire for about a year on his truck, didn't do anything until he needed an inspection. I suspected a clogged injector, put a can of bg44k in and drove it. I tell you, it was just bogging along for miles. All of a sudden, it started to shimmy while driving. I thought his transmission was probably failing too, but the darn thing started becoming alive! It became so responsive and strong. Try it. If you don't feel it working, it is beyond something that can be fixed by putting something in the tank. I too, am a fan of MMO in the tank, but it has to be used all the time in order to be effective. Further, if you have lots of blow-by, you'll get lots of soot coming back into your intake through the pcv and caking onto the valves as well. Not so sure the oil catch can or the techron is effective enough in your case. Ebay or some local car dealerships have it, call around. goes for around $20 a can. You can try intake valve cleaner sprays, but they're not effective enough in my opinion because you have no direct access to the valves. On the other hand, the bg44k is constantly sprayed onto the valves throughout the use of the fuel in the tank, and you also get your injectors cleaned at the same time. works best on short trip driving, because it gives time for the sooty stuff to absorb it over and over again and break apart.
 
#18 ·
Yes, in my opinion. I have used seafoam with SOME results, placebo results perhaps hehe. bg44k on the other hand, you can feel the difference. I'd say, if you don't get a result with bg44k, and you have been good with the maintenance with the mmo and techron, that you most likely have another problem than deposits or injectors. That's when the list grows exponentially. Egr plugged passages or stuck open, catalytic converter starting to clog up, MAP and/or MAF sensor, throttle body deposits, IAC valve sooty.....I'd try the BG, good luck.
 
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