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    Thread: Weird misfire error

    1. 05-10-2020 01:20 PM #1
      Hello, I hope I’m posting this in the right area. I own a 2007 VW beetle with 2.5l and am having an odd situation. Whenever the temperature in the summer time reaches the 90s to 100s my engine after being driven for 30 minutes to an hour will tend to start misfiring in cylinder 4 and 5. This will cause the car to start to decrease in speed, which can be really bad on the highway. The main issues I have with trying to get a diagnostic is that by the time my car can be taken to the shop and by the time they are able to get around to it, the car has cooled down enough that the issue is gone. I have no engine temperature reading which also makes it difficult to tell if it is overheating, but by feeling the heat from the engine it is definitely hot. Any ideas would be greatly appreciated.

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    3. 05-10-2020 01:22 PM #2
      I'd try a full tank of higher octane fuel. If that makes no change, try changing spark plugs and coils as a starting point

      Sent from my SM-G930V using Tapatalk
      09 JSW SE 2.5 5 speed 153k
      08 Jetta S 2.5 5 speed 238,000 miles on the original clutch, lost to black ice

    4. Member nekkidlad's Avatar
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      2008 VW Rabbit 2.5L M/T
      05-22-2020 11:31 PM #3
      Quote Originally Posted by jethead102 View Post
      I'd try a full tank of higher octane fuel. If that makes no change, try changing spark plugs and coils as a starting point

      Sent from my SM-G930V using Tapatalk
      I’d start with swapping coil packs on the cylinders. It’s free and takes only a few minutes. If the misfire changes w the coil packs it’s the coil packs are bad, if it’s stays in the same cylinder it can be a spark plug or fuel injector problem(most likely plug, because bad injector would be more of a constant problem, not with temp change). If the misfire didn’t change moving coils around, try swapping spark plugs around and see if that changes the misfire. If it does you know it’s the plug, if it doesn’t it’s the fuel injectors or something wrong with the cylinder/valves.

      I’m willing to bet it’s just bad coils. When you swap them around check the bottom of the coils for oil to see if the valve cover gasket may be leaking compounding the problem.

      What’s your mileage? The coil packs are known not to last much longer than 80-100kmi. Also the interval for spark plugs is like 40kmi. If the plugs haven’t been replaced I’d strongly recommend that you do if you replace the coils, and I strongly suggest Vw or ngk plugs(lots of horror stories around the forums with other brands).

      You can do both the plugs and coils for around $150 shipped or less if you look around online. I personally paid $150 when I did mine about 2 months ago w parts from rock auto(I highly recommend them if you’re on a budget, lots of options on low priced parts).

      After that I’d personally dump a can of seafoam/berryman or equivalent fuel system cleaners(not one of those dollar or 2 “fuel system cleaner” HEET/Techron or whatever bottles)through the fuel tank(follow mixing ratio instructions). But that’s just me.
      Last edited by nekkidlad; 05-23-2020 at 08:52 AM.

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    6. Junior Member 2.5T\/DUB's Avatar
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      Aug 1st, 2020
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      Alabama
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      2005.5 VW Jetta 2.5T
      08-01-2020 03:07 PM #4
      Dying fuel pumps can do this, will also mess the fuel gauge and mile-to-empty on the LCD display. Higher ambient temps makes everything work harder, older parts especially will show their age.

      Given the age of the 2007 2.5, I would replace the following:

      fuel filter
      spark plugs
      ignition coils
      fuel injectors
      fuel pump

      Misfire codes are normally cause by spark and/or fuel issues.

      Just a thought.

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