P0301 cylinder 1 misfire
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  1. #1
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    P0301 cylinder 1 misfire

    I have a 99 Volkswagen Passat 1.8 Turbo Automatic AEB engine. I recently did a rebuild on it and ever since I keep getting this code P0301 that says "cylinder 1 misfire". The engine is also running rich and the spark plug in cylinder 1 keeps getting gummed up. I've changed the coil and the spark plugs and the injectors and it helps temporarily but then the problem keeps reoccurring. Any help you could give me would truly be appreciated.

    Thanks,

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  3. #2
    Super Stealth Retired Moderator JayTheSnork's Avatar
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    are you sure it is running rich? how do you know? have you hooked up any device to read any ECU error codes?

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    Motel Room Moderator VAGguy's Avatar
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    Have you ever replaced the ICM on the airbox? Generally, a bad one misfires on #2 but it's worth performing the diagnostic procedures on it to see. I think it's in the info forum.

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    Thanks for replying so quickly, I didn't realize anyone had replied yet because I thought I would get an email informing me of any replies so I will check the forum daily now that I know I won't get notice so sorry it took me so long to answer.

    I'm pretty sure it's running rich because the exhaust is coming out very dark and the spark plug keeps getting gummed up. I hooked up a scan tool and it keeps saying cylinder 1 misfire and it displays the code P0301.

    I'm not sure about the ECM if it's the same as the ECU I did replace the ECU and your right before I replaced it it kept reading misfire on multiple cylinders and #'s 1 and two kept coming up. After I replaced it I didn't have any problems other than it running rich and the spark plug in cylinder one kept getting gummed up. I did get the ECU at a salvage yard but I don't think it has gone bad because it still runs where as before it wouldn't run, I would give it gas and it would stall on me.

    Any clues on what it could be?

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    Motel Room Moderator VAGguy's Avatar
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    Now, I am confused. ICM or ignition control module (on airbox). ECU/M, Engine control unit/Module(driver side base of windshield in battery compartment).
    Any other codes? What plugs are you using? How are the condition of all of your vac hoses/lines?

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    misfire cylinder #1/1.8 turbo automatic AEB engine

    I checked the vac hoses and they seem to be in good condition and working right. Anything in particular I should be looking out for with them? The ECU I changed is the one in the drivers side air box. I was using NGK plugs.

    I did a compression test on all 4 cylinders and cylinder 1 has absolutely no compression, I don't understand that because we changed the rings on all the cylinders. Someone told me this could mean a blown head gasket but when I did the rebuild we changed the head gasket as well. Is it possible for the rings to have gone bad in cylinder one even though it is brand new? All other cylinders tested at 150. They also said it could be the valve and incidentally I didn't get the head machined because I had just done that back in 2006 when my timing belt went out. I originally did the rebuild because I had lost oil pressure and the rod in cylinder four started banging. We did everyting by the book and I used a Bentley & Haynes manual but the guy that helped me said we didn't need to do any head work on it because the same thing happened to him with an Audi same exact engine and he said his was fine so I didn't worry about it. Could this have been a mistake? Do you think it could be the Valve? Anything else I could possibly check before taking the head off?

    Someone else said that if the car ran fine at first that maybe a vacum leak could have damaged it, is that really possible?

    I finally had the car running fine and right before this happened I was on the way to work and the car had not completely warmed up yet and I accelerated to try to merge on the interstate and that is when the check engine light came on, then it quit flashing but remained on and stabelized so I accelerated once again and the light started flashing and the car started running rough again and has ever since.


    Thanks,

  8. #7
    PZ
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    I would pull the valve cover and rotate the engine by hand. Look to see if the cam lobes pull away from the lifters when the valves should close. If so, the valve is bent.

    Did you do both a wet and dry compression test? A wet test would point out a ring problem (usually).

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    misfire cylinder #1/1.8 turbo automatic AEB engine

    What is a wet compression test? A friend of mine told me to pour a little bit of oil in the cylinder and then do the compression test. Is this what you mean? I did do that and the compression went up a tiny bit but hardly nothing at all (15).

    Thanks,

  10. #9
    PZ
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    Yes, the oil in the cylinder is a wet compression test.

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