P0302 cylinder two misfire

2001 VOLKSWAGEN GOLF
112,000 MILES • 1.6L • 4 CYL • FWD • MANUAL
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SZáVó ZSOLTI
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Hello. I have the car listed above with 16v with petrol engine. I bought it in October, and i had a check engine light. Went to service, it gave me P0402, EGR excessive flow and P0302 cylinder two misfire. I changed the spark plugs obviously when i bought the car, ignition coil in December and EGR valve one week ago, both new ones, and two days ago the check engine light was back. I put it on a tester, and same trouble codes. Also i got a rough idle (600 rpm), sometimes it drops even to 400 rpm when the engine is already warm, and saves from cutting off, pushing up to 1000-1200 for a second. There are no other trouble codes, besides once i got P0171 System too lean, but when it got removed it, never reappeared. What could be the problem? (On the right bottom corner you can see the dates, when the trouble codes occurred. One is with the sensor code as well, that is when we tried how the car works without EGR valve on).
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Jan 21, 2017 at 2:18 AM
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STEVE W.
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A partly clogged converter could cause the excess EGR flow and the lean condition as well as the misfire. Run an exhaust back pressure test and look at the O2 sensors to see if this is the case.
https://www.2carpros.com/articles/how-to-test-a-catalytic-converter
Jan 21, 2017 at 4:20 AM
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SZáVó ZSOLTI
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Hello again. Thanks for your answer, but im sad it didnt work out. I've been on several places, trying to repair, they checked the catalytic converter, and that seems ok. All of them said its different problem the EGR and the misfire, so we tried adapting the EGR with a VAGCOM cable, and it seemed to work fine. The misfire after replacing ignition coil seemed to be gone, but then it came back, and also had problems with 2nd injector aswell. I've replaced it yesterday, still rough idle, and sounds like coughing. Any ideas?
Jan 28, 2017 at 1:50 PM
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SATURNTECH9
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What are the exact code numbers not code descriptions that you have in the computer?
Jan 28, 2017 at 10:14 PM
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SZáVó ZSOLTI
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P0402 EGR excessive flow, P0302 Cylinder 2 misfire, and sometimes P0171 System too lean. If you meant the other 5digit code (or maybe im wrong and not 5digit) before them, sadly now i cant check it, and with my simple OBD2 cable its not appearing. The big RPM drops seemed to be gone after EGR adaption, but its still not a stable idle, moving between 650-750, and maybe the exhaust sputtering causes the car to tremor.
Jan 29, 2017 at 2:49 AM
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SZáVó ZSOLTI
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The next day on tester it still showed the EGR excessive flow code, but w/o check engine light, so maybe it wasnt just cleared after adaption, i dont know. I will go only Wednesday to service, i'll say them to check the vacuum leak. Havent done smoke test, how i have to do that, and what i check by that?
Jan 29, 2017 at 10:00 AM
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SATURNTECH9
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A smoke test is a accurate way of using smoke injected into the intake and vacuum lines etc.It takes a professional smoke tester or a homemade one.I have a homemade one there expensive the professional ones.As far the code it might just have not been cleared.Those pcv a lot of the time leak excessive vacuum into the valve cover.So a smoke test won't reveal its bad.Is the misfire constant?
Jan 29, 2017 at 2:36 PM
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SZáVó ZSOLTI
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Well i dont know how i could do that smoke test, or at my local shops they know how its done, but maybe they know how to check the pcv and the other vacuum lines. By the way after code remove, the code is not coming back for like 100-150 km, but then check engine lights on. The sputtering by the misfire is not constant, its not having like a rhytm or i dont know how to say that, and also the RPM has a few stable moments, but mostly running rough on idle. During driving i cant experience that, there is no loss of power or anything like that, just moves almost like a 105hp car should move. When the engine light comes on, the engine is working with 3 cylinders, the lose of power and stability feels obviously, but on engine restart its like everything fine, except the idle rpm and the exhaust caughing.
Jan 29, 2017 at 2:50 PM
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SATURNTECH9
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Swap the coil from number 3 to number four and see if the misfire moves to number four.Also a shop should know how to perform and smoke test.
Jan 29, 2017 at 3:34 PM
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SZáVó ZSOLTI
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The cylinder 2 is the faulty one, i mean thats the one with fault codes. I've tried swapping sparks, ignition coils, injectors, but the misfire remained there.
Jan 30, 2017 at 2:45 AM
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SATURNTECH9
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Have you performed a compression test yet?
Jan 30, 2017 at 6:14 AM
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SZáVó ZSOLTI
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Yes, and the compressions were ok on all cylinders.
Jan 30, 2017 at 6:28 AM
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SATURNTECH9
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Vacuum leaks can cause a Miss fire also.
Jan 30, 2017 at 12:36 PM
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SZáVó ZSOLTI
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I'll go Wednesday to the service, and im going to ask him if he can do the smoke test, or if he got any tricks for vacuum leak test. After that im coming back with the result. Thanks alot.
Jan 30, 2017 at 12:42 PM
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SATURNTECH9
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Smoke is the best way to find vacuum leaks.
Jan 30, 2017 at 12:54 PM
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SZáVó ZSOLTI
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Yes i hope he can do it. And also i'd ask something, the vacuum leak can cause the rough idle and the exhaust coguhing-sputtering?
Jan 30, 2017 at 1:00 PM
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SATURNTECH9
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It sure can cause all that also check the pcv that can cause all that also.
Jan 30, 2017 at 1:17 PM
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SZáVó ZSOLTI
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I hadn't been driving this car for a while, but my mom did, the codes has been deleted several times. Now the check engine light is gone, no more codes (on 600+km, before it came back after 100-150km), no more RPM drops to 400-500, it has a stable ~800, but i still have the exhaust sputtering, the rough idle, and also what i noticed, when the brake pedal gets depressed, i hear a hissing noise. Checked most of the vacuum lines, one of them was manually fixed, with insulating tape and cable tie , thats the vacuum pipe which is at the brake booster (like the serviceman told me, tomorrow im going to check it and take a picture of it). That pipe can cause the break pedal hissing noise, the exhaust sputtering and the rough idle aswell? Also is it real, if i clear a code 50 times, it wont come back? Thank you very much.
Mar 5, 2017 at 2:03 PM
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SATURNTECH9
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Iam not sure what your asking about the 50 times part.A vacuum leak with cause a rough idle high idle could cause misfire etc.If it was hissing when stepping on the brake I would think the brake booster is leaking vacuum.But fix the vacuum leak to the brake booster for sure.
Mar 5, 2017 at 8:14 PM
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SZáVó ZSOLTI
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So this is the leak, i tried fixing it, i dont know if it worked or not. Something what i've noticed, when the AC is off, RPM is around 600, exhaust sputtering, rough idle, but when its on, RPM is around 800, no exhaust sputter, relatively ok idle. https://youtu.be/KGE299_Lz6I Here is the video to prove. What can cause this? I've called today 3 different servicemans, none of them had an idea why is this.
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Mar 6, 2017 at 10:11 AM
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SATURNTECH9
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If there is a barb on each end of that hose under the hard plastic line you can replace the hard plastic line with a rubber hose.Also again a vacuum leak could be causing all those issues start by fixing that vacuum leak.You might just have to get a new hard plastic line.
Mar 6, 2017 at 12:34 PM
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SZáVó ZSOLTI
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Today that hose has been fixed, and this time i've been to another serviceman. I'm adding the image of the old hose, its awkward its fixed in 3 places.. So back to the problem, while the other guy said both of the O2 sensors are allright, this serviceman noticed the first O2 sensor might be faulty, because its value is oscillating around 0.43V and 0.48V meanwhile the second has the good values, moving between 0.1V and 0.9V. I've seen on internet, when the mixture is good, its on 0.45V, and going up/down correcting the mixture. I would ask it, is it really faulty? While he tested it, he got the System too lean (Bank 1) fault code aswell. Can this be the cause of the relatively high idle consumption aswell?
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Mar 8, 2017 at 6:52 AM
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SATURNTECH9
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If the o2 sensor not moving much is sensor two the down stream one by the cat?That would be normal at idle and when you raised the rpms up to about 2000 then the o2 sensor would start moving.That o2 sensor is to read the health of the cat.I would have a smoke test performed on the vacuum system you probably still have a vacuum leak.
Mar 8, 2017 at 12:51 PM
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SZáVó ZSOLTI
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The second one was moving ok. The first one has only low amount moves between 0.43 and 0.48, even when we raised the rpm to 3-4k. So you are saying that the first o2 sensor with this move is ok, its not faulty?
Mar 8, 2017 at 1:05 PM
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SZáVó ZSOLTI
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I've found no one who can perform a smoke test.. I don't know, this country is fucked (Hungary), atleast the car mechanic part of it.
Mar 8, 2017 at 1:06 PM
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SATURNTECH9
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That's electrical tap on the hose is not a good fix for the vacuum leak I didn't look at the picture before my last reply your probably best just replacing that hose you can probably find one on eBay.Also the readings not moving sounds like your talking about the sensor down by the cat.Unplug the top sensor and see how that effects the readings?Because it makes a lot more sense that one not moving much is the bottom one.
Mar 8, 2017 at 1:12 PM
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SZáVó ZSOLTI
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That hose (which i added the image about) was changed with a new one, but i've seen something interesting yesterday, the short and long fuel trims (Image attached). By the way i've already ordered the Bank1 O2 sensor, i got it for only ~28 dollars, for a try to fix the problem its not a big investment (compared to injectors and EGR valve). Its possible i have a bad O2 sensor, AND still atleast one more vacuum leak? Also i've seen on the internet, an absolutely dirty air filter also can cause the rough idle stuff, tomorrow i'm going to check it aswell (as far as i know it hadnt been checked when we bought the car, half year ago).
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Mar 9, 2017 at 1:03 PM
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SATURNTECH9
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Or the o2 sensor is just picking up the lean condition and reading lean.
Mar 9, 2017 at 1:28 PM
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SZáVó ZSOLTI
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The first picture is the cable of the current bank1 o2 sensor, the second the pipe from the plastic label, air filter. I hear a hissing sound, probably from that pipe, that can effect the air-fuel ratio? I will try taping it, to see if it makes the temporary fix.
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Mar 10, 2017 at 1:06 AM
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SATURNTECH9
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Again any un metered air/vacuum leak will set a lean code and can effect the way it runs.Taping the hose isn't the way to fix it.
Mar 10, 2017 at 7:07 AM
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SZáVó ZSOLTI
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I've seen on the internet i can do a smoke test with cigar/vape. I'd ask it, which hose should i blow into? Also i installed the other O2 sensor (on the picture the left one is the old one), i got good values with it in voltage, also the short and long term fuel trims are good, but the exhaust is still sputtering, and the idle is relatively rough, but feels a bit better now. Does it have an adaption time? I've heard something like that it has to adapt to the new sensor.
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Mar 11, 2017 at 6:16 AM
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SATURNTECH9
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No it should start working right away the new sensor.As far as the cigar deal tried that in a pinch I didn't like the results.I made a smoke machine with a old metal paint sprayer GM glow plug some miles hoses fish pump wires fuse etc and some unscented mineral oil.It works great.
Mar 11, 2017 at 1:09 PM
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SATURNTECH9
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Not miles ment nipples
Mar 11, 2017 at 1:18 PM
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SZáVó ZSOLTI
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We've been looking for vacuum leaks with Carb cleaner (with engine on), and there is no more leak, even the tube which i've posted a picture about, is not leaking. With the O2 sensor, i got better short and long term fuel trims, but now i got a double code for misfire, and the engine is constantly misfireing, i can hear the sputter on the exhaust. Im absolutely lost right now, what the hack it could be.
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Mar 12, 2017 at 12:35 PM
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SATURNTECH9
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Can you swap the number two spark plug and coil with the number 3 spark plug and coil?to see if the misfire moves ?
Mar 12, 2017 at 6:24 PM
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SZáVó ZSOLTI
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We already tried that, few weeks ago. Only ignition coils swap, but misfire remained in cylinder 2.
Mar 12, 2017 at 10:28 PM
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SATURNTECH9
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Does it only missifire at idle constantly or when you rub it to as well?
Mar 12, 2017 at 10:40 PM
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SZáVó ZSOLTI
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I can feel it only at idle, it got no loss of power while driving.
Mar 12, 2017 at 10:44 PM
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STRAILER
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Lets see if you have low compression on #2 here is a guide that will help you

https://www.2carpros.com/articles/how-to-test-engine-compression

Please run this test and get back to us so we can continue helping you.

Best, Ken
Mar 15, 2017 at 12:41 PM
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SZáVó ZSOLTI
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I dont know the exact numbers of the pressures on the cylinders, but i know it was tested, i think in january, and the serviceman said its good on each cylinder.
Mar 15, 2017 at 12:53 PM
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SATURNTECH9
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It would be nice to know the exact readings.So now we're back to a vacuum leak that can cause a miss at idle but not at higher rpms.
Mar 15, 2017 at 12:59 PM