- P0304 & Shuddering Under Acceleration
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    1. 03-03-2019 12:27 PM #1
      Hi all,

      Hoping I might be able to gain some insight in this forum as well with the issues I've been having.. Original Thread In Jetta Forum

      After being at the dealer for nearly two weeks while they figured out the extended warranty coverage, they eventually diagnosed that the cam chain had skipped one tooth. They ordered the parts in (which was a minor debacle in and of itself), and replaced the chain, one coil pack, and all spark plugs. All told, I'm on the hook for my deductable, the spark plugs/labour, and about an hour of labour while they investigated a possible rodent issue, which they determined was minor and wouldn't cause any issues. They did note that there was carbon buildup that would need to be dealt with sooner rather than later, and that would still be causing the uneven idle on cold starts, but I shouldn't see any further stalling, as that was due to the cam chain. I got the car on Friday evening, and aside from the cold start idle issue, it was much improved.

      I drove around all day on Saturday, and it was fine. Later in the day when I went to pick up my wife, I pulled out to pass a slower car, and there was a distinct shuddering under acceleration, which I've not encountered before, and primarily in third gear and higher. This occurred a couple of more times under light acceleration. I pulled over and plugged in my code reader, and this time it pulled a P0304 (misfire on cylinder 4), and eventually a check engine light came on. From what I've read, this seems like it's likely due to a bad spark plug (possible, given that they were just changed), bad injector coil, or a blocked fuel injector, which may be related to the carbon issue. Any thoughts as to other possible causes?

      Whatever the root cause may be, it's going back to the dealer first thing on Monday.

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    3. 04-08-2019 11:33 PM #2
      Hey I had a check engine light come on with an error code P0301 misfire cylinder one, changed out all the plugs all the coil packs and the car ran great. About three days later I was on the highway (yesterday) shifted in the six gear and about 3000 RPMs I got a shuttering and loss of power. Then today continue to get worse and it would shut her throughout third and fourth. Check engine light only really comes on while it’s shuttering and it’s blinks for a bit and goes away. Also my ecu ligjt has being going on an off aswell?

    4. 06-15-2019 09:42 AM #3
      Ok, a long overdue update to this:

      I took the car back to the dealer. They had it for an entire day and said the new misfire was due to carbon buildup. That didn't make a ton of sense, as this misfire was very different to what I had been experiencing previously. I took it to another shop, and they diagnosed a bad ignition coils and replaced them. That problem was fixed, and has not returned since.

      However, since then, things have taken more turns. After driving the car for another couple of weeks, it settled into the same pattern of behavior of having misfires within a few minutes of first starting up, and then about a week after that, it then started stalling occasionally when coming to a stop. After one particularly bad round of stalling, the check engine light came on again, and pulled the P0016 code again. However, after a couple of drive cycles, the light went away.

      I took the car back to the dealer, as the P0016 code coming up again was clearly a cause for concern. I talked to the same person I had been dealing with thus far, and he refused to look at my car, as he said it the misfires and stalls were 100% due to carbon buildup. I took issue with that, and escalated to the service manager. The manager was excellent, and acknowledged that they hadn't handled my problem properly thus far. They had one of their lead techs go out and scan my car while I described the problems I was having. They acknowledged that there was a minor chance that the timing chain replacement may not have been done correctly, hence the continued issues, so they took the car in again to investigate.

      That investigation showed that the timing was correct, and that there were no issues with the timing chain or the tensioner. They did say that the carbon buildup was severe - "It looks like the surface of the moon" was how it was described to me. So, given that the next step was to get the carbon cleared up. That was done, and the car ran great - the engine was quiet and smooth, and no sign of any problems. Then I left work about four days later, and at the first stop light I came to, the misfire at idle returned. I took it back to the dealer the next day, and they were puzzled. They drove it for a bit, and couldn't detect any problems. They put a fuel system cleaner in the tank, as they said there was a chance that there was some gunk on the injectors that was causing this problem. I drove the car for another couple of weeks, but the cold start idle misfires continued, albeit not quite as severe as before. Then it started stalling when coming to a stop again. Just like every other time with this issue, eventually I came to a round of stalling that was bad enough to cause the check engine light to come on, and yet again P0016 comes up. Back to the dealer we go...

      They were very confused by this continuing. They had the car for the past week, and determined that the throttle body was dirty and needed to be cleaned. They did so, and drove the car for two days afterwards to see if there were any further instances, but they had no issues with idle misfires or stalling, so they returned the car to me. On my way home, the car nearly stalled while I was making a left hand turn, and the engine was not smooth in general - one trait I've noticed is that when I get off the gas and coast, I feel a brief kicking sensation, which is not present once the car is warm. I plugged my code reader in, and it pulled a pending P0011 code.

      Yesterday morning, the car started misfiring while it was warming up in the garage. This settled down after I revved it to 2K RPM, but it came back with a vengeance two stop lights later. Typically it bounces in about a 200 RPM range, but this time was about 600 RPM, and caused pronounced shaking. Eventually the TCS light came on, and I pulled pending codes for P0300, P0301, and P0304. But just like every other time, once the car is fully warmed up, there doesn't seem to be much of an issue. Back to the dealer yet again...

      My dealer is stumped at this point. I went for a drive with one of their techs, but given that the ca was warm, there were no repeats of the issue. All the obvious mechanical elements seem to have been dealt with so far. To recap, here's the work done since February:

      • Timing Chain
      • Cam Chain Tensioner
      • All Ignition Coils
      • All Spark Plugs
      • Carbon Cleanup

      Additionally, they've investigated the oil system, and determined that there's no issues with blockages or pick-up. Given all this, I'm not sure what else to look at. Is this possibly due to an electrical fault, or a bad sensor? Is it maybe fuel system related? Any insight would be appreciated.
      Last edited by jbrown604; 06-15-2019 at 09:48 AM.

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    6. Junior Member
      Join Date
      Mar 16th, 2019
      2017 Passat SEL Premium, 2016 Jetta SEL Premium (RIP)
      07-03-2019 12:00 PM #4
      Lemon it

    7. 10-07-2019 01:17 AM #5
      Ok, time for another update.

      The diagnosis that my dealer came up with during the last round of issues in June was that the issues were due to oil sludge. They suspected that was probably rooted in the previous owner having now done an oil change, with the first one being done when I took over the car at approx. 15,000km's. They claimed to have flushed out as much of the sludge as they could, but that they would not be able to remove all of it. They advised that I change my oil every 7,500km going forward, and to do an oil flush with every change. I'll be the first to admit that this seemed like an odd diagnosis to land on after they had already determined that there was no problem with the oil system, but the problems that I had experienced previously have not reappeared since then...

      Until today.

      I had left in the morning, and after driving down the highway for approx 5km's, I took an off-ramp and was stopped at a red light. Then the misfire began again, just as it had in the previous months. I was able to keep driving, but everytime I came to an extended stop, the misfires would begin again, until the car had properly warmed up. Once I was able to park, I plugged my code reader in, and it pulled a pending P0011 code (no CEL). I did some basic troubleshooting, and noticed that my oil was just heading into the low territory on the dipstick. This seemed somewhat unusual, as it was only 6,500km's since it's last oil change at the dealer.

      Given the low oil level, I got an oil change and filter change done today. The engine is notably quieter and smoother. Additionally, a recent behaviour where the car felt particularly clunky when getting off the gas seems to have improved measurably with the oil change.

      I also checked some of the logs I was able to pull from when I had my code reader plugged in while the car was misfiring. The one thing that jumped out to me was how erratic the Fuel Rail Pressure readings were. For reference, a typical idle reading once the car is warmed up is approx. 5000kpa. When the car was misfiring at idle, this was jumping between 5000kpa to nearly 12,000kpa, with it typically rapidly bouncing between 9000 and 10,000kpa. I don't know if this is actually indicative of anything or not, however.

      So, I guess I need to head back down the road of trying to figure out what this problem is yet again...

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