2000 5.4l lariat. My cylinder 1 for 2 years has been poping p0301code and has a rough idle at start for about 30seconds it also has a little white smoke for that 30seconds. new cop, new spark plug, new spark plug pig tail, swapped injectors to different cylinders multiple times to change code no luck. Compression dry and wet are at 200 and all cylinders are within10%. I had a dorman intake manifold installed 4 years ago and the code came a few years after. Im thinking intake manifold gasket is bad between cylinder 1 and the heater bypass tube allowing coolant to slowly leak down into the cylinder causing my rough start. I looked through the injector hole but could not tell. With all the info I have given is there any other places or things that it could be before I do a gasket replacement or is all my tests leading to the intake manifold gasket
If your using a small amount of antifreeze, your probably buring it and causing the rough idle as you guessed. I had the same thing on my older truck. Not necessarily the manifold, could be a pin hole in the head gasket also. Depending on what you want to spend and how much time you want to invest, you could try a sealer. I had very good luck with BARS Copper gasket sealer . It would last about 1 year, then i would flush and do it again. Did that for 45K miles ( 3 years). I like the copper because if mixes with the antifreeze, dont have to remove it.
Thank you steve I will look into that. I do have the gasket ready in hand for the tear down. Maybe ill try the leak stop first. I would still like to know what people think maybe the issue . Im going to try UV die in the coolant. Then pull the injector and see if the UV light apears in the hole indicating there is a coolant leak. Oh man I forgot to put in the original post that I had performed a cooling system pressure test and it passed. held 16psi witch is the system rating for 10 minutes before releasing the pressure. Any clues to what maybe my problem or even other test. I don't mind putting time and a little money into this truck so please post more info thanks
had the same issue you describe with my brothers 2000 explorer with the 4.0 ohv, and same as your thinking,the seal got weak and let coolant seep into cylinder and give rough startups until it dried out, pulled intake and changed gasket,resolved issue, i would say run it a day, let it set til the next day and pull the plug and check for any coolant in the cylinder, may be a minimal ammount but enough to throw everything out of whack. thats how i tested his atleast to find the issue