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VW Golf 4 2.0 AZJ Engine: Misfire, Power Loss on Wet/Cold Days, Idle Issues, Thermostat Replacement

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  • #1 16652930
    ondrei
    Level 9  
    Posts: 167
    Rate: 43
    I warmly welcome. I have a VW golf 4 combi engine 2.0 115km, symbol AZJ. I've had it for two years. After firing on damp days or on cold days after acceleration, regardless of what fuel I have the ignition on, it starts to jerk slightly and I have no power, the problem disappears after driving a few kilometers when I get the right temperature (about 60 ') then it accelerates it flows in higher gears sometimes jerks when I move and when I throw a double. It wavers slightly at idle regardless of the temperature. In June, I replaced the ignition wires and candles (all for NGK) I'm thinking about replacing the coil and modules, what do you think. Fall is coming and you know it will be cool and humid. I would also like to add that I think I have a thermostat to replace I am heating well but it does not catch the full 90 ". And if in your opinion the coil to be replaced is it a complicated operation?
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    #2 16652956
    sulof1601
    Level 26  
    Posts: 598
    Help: 94
    Rate: 280
    Hello. It looks like a module coil. The replacement is not difficult, see if it is cracked visually.
  • #3 16652964
    ondrei
    Level 9  
    Posts: 167
    Rate: 43
    sulof1601 wrote:
    Hello. It looks like a module coil. The replacement is not difficult, see if it is cracked visually.


    it is not cracked. Tell me more about the trade. What to unscrew idt. How long does it take
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    #4 16653004
    sulof1601
    Level 26  
    Posts: 598
    Help: 94
    Rate: 280
    You detach the HV cables and one ankle, and probably four screws. You have good access to everything from the front. You changed the wires, you know where it is 20 minutes and that's it.
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  • #5 16653037
    ondrei
    Level 9  
    Posts: 167
    Rate: 43
    sulof1601 wrote:
    You detach the HV cables and one ankle, and probably four screws. You have good access to everything from the front. You changed the wires, you know where it is 20 minutes and that's it.


    now just which coil to choose
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  • #6 16653039
    sulof1601
    Level 26  
    Posts: 598
    Help: 94
    Rate: 280
    Beru albo NGK
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    #8 16653081
    sulof1601
    Level 26  
    Posts: 598
    Help: 94
    Rate: 280
    Yes, the module is built-in, that's why the coil is called the module, even though it can be saved in the catalog as an ignition coil.
  • #9 16653097
    ondrei
    Level 9  
    Posts: 167
    Rate: 43
    sulof1601 wrote:
    Yes, the module is built-in, that's why the coil is called the module, even though it can be saved in the catalog as an ignition coil.


    Thank you very much. Tomorrow evening, I will write how it went and whether it helped
  • #10 16653774
    grala1
    VAG group specialist  
    Posts: 9812
    Help: 1495
    Rate: 5036
    The original is a TEMIC coil.
    It does not have to be a coil, but can be HV cables.
    Sprinkle the wires with water from the sprinkler without soaking the coil - it turns out.
    I don't know about it, but in 2.0 AQY you have to disassemble the secondary air pump to get to the coil screws and remove it.
    AZJ has a different intake manifold, so it may be different.
  • #11 16654938
    ondrei
    Level 9  
    Posts: 167
    Rate: 43
    grala1 wrote:
    The original is a TEMIC coil.
    It does not have to be a coil, but can be HV cables.
    Sprinkle the wires with water from the sprinkler without soaking the coil - it turns out.
    I don't know about it, but in 2.0 AQY you have to disassemble the secondary air pump to get to the coil screws and remove it.
    AZJ has a different intake manifold, so it may be different.

    as I mentioned, the wires were replaced earlier. Today I replaced the coil, it turned out that it was slightly cracked underneath. I'm going on a longer route in a moment, it will turn out if it helped. The old coil was the original temic I founded the NGK company. The entire replacement operation took about 20-30 minutes

    Added after 2 [hours] 39 [minutes]:

    sulof1601 wrote:
    Yes, the module is built-in, that's why the coil is called the module, even though it can be saved in the catalog as an ignition coil.


    The coil was cracked you can see a clear improvement, the engine works much better and I do not jerk when accelerating. I will describe how it will behave on cooler days and in higher humidity, as soon as there is an opportunity. And I thank you with all my heart
  • #12 16659423
    ondrei
    Level 9  
    Posts: 167
    Rate: 43
    Hello everyone, today it was quite humid and cool morning, the car was running smoothly, which is the obvious fault of the coil. Special thanks to sulof1601, I am very grateful to you for your expertise. With the wishes of one forum member, I will discuss the exact process of disassembling the old coil in my AJZ model. The first step is to disassemble the secondary air pump, as a colleague wrote above, it is not a complicated operation, but requires a little patience, especially with the engine screw, you need a small ratchet with a broken tip and on a stick, then disconnect the plug from the pump and move it to the side and a coil will appear to our eyes. I signed each HV cable and then dismantled it. The only thing left is to disassemble the coil itself, these are 3 torx screws (I don't remember which one) and our coil, after removing the coil, we have to remove the plug and install a new one
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Topic summary

✨ The discussion revolves around a VW Golf 4 with a 2.0 AZJ engine experiencing misfires, power loss, and idle issues, particularly in wet and cold conditions. The owner replaced ignition wires and spark plugs with NGK components but continued to face problems. Suggestions included checking the ignition coil, which was confirmed to be cracked upon inspection. The replacement process was described as straightforward, involving detaching high-voltage cables and unscrewing the coil. The original coil was identified as a TEMIC model, and the owner successfully replaced it with an NGK coil, resulting in improved engine performance. The discussion also touched on the importance of checking high-voltage cables and the potential need for thermostat replacement due to inadequate temperature readings.
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FAQ

TL;DR: AZJ 2.0 misfire on wet/cold starts was fixed by swapping the coil pack; “20 minutes and that’s it.” — an expert said. [Elektroda, sulof1601, post #16653004]

Why it matters: This FAQ helps VW Golf 4 AZJ owners diagnose jerks, idle wobble, and cold-start power loss quickly and cheaply.

Quick Facts

What common symptoms point to a failing coil on the AZJ 2.0?

Slight jerking after start on damp/cold days, weak acceleration until about 60°C, and a gentle idle wobble. These symptoms persisted regardless of fuel, then disappeared as the engine warmed. That pattern strongly implicates the coil pack on this engine. [Elektroda, ondrei, post #16652930]

Is the ignition module built into the coil on this engine?

Yes. The AZJ setup integrates the ignition module into the coil assembly, so the part is often listed as a coil or coil module interchangeably. [Elektroda, sulof1601, post #16653081]

Which coil brands did owners use or recommend?

Thread experts advised Beru or NGK. The reporting owner installed an NGK unit and confirmed improved performance after replacement. “Beru or NGK.” [Elektroda, sulof1601, post #16653039]

How long does it take to replace the coil?

Expect about 20 minutes if you know the layout, using basic hand tools. One poster reported a 20–30 minute swap during their driveway repair. “20 minutes and that’s it.” [Elektroda, sulof1601, post #16653004]

Do I need to remove the secondary air pump to reach the coil on AZJ?

Yes. The owner walkthrough shows removing the secondary air pump first for access, then the coil with three Torx screws. Label HV leads before removal. [Elektroda, ondrei, post #16659423]

What’s the quick driveway test for bad HV wires versus a bad coil?

Mist the HV wires lightly with water while avoiding the coil. If the engine stumbles or arcs appear, suspect the HV leads. If not, the coil pack may be at fault. [Elektroda, grala1, post #16653774]

What was the real-world fix outcome after coil replacement?

A cracked original TEMIC coil was replaced with NGK. The car then ran smoothly on a humid, cool morning, and acceleration jerk disappeared. [Elektroda, ondrei, post #16654938]

Which screws secure the AZJ coil, and how many are there?

The coil is held by three Torx screws on the AZJ. Access improves after removing the secondary air pump as described by the owner. [Elektroda, ondrei, post #16659423]

Any edge cases or model differences to watch for?

Yes. On the 2.0 AQY, access to the coil screws requires removing the secondary air pump. Layout differs from AZJ due to intake variations. [Elektroda, grala1, post #16653774]

Should I label the HV cables before pulling them off the coil?

Yes. The owner labeled each HV lead before removal to avoid cross-connection during reassembly. It kept the job clean and quick. [Elektroda, ondrei, post #16659423]

My temp won’t reach 90°C—could the thermostat cause misfires?

In the thread, a low temp reading coexisted with misfires, but the misfire resolved after coil replacement. Treat thermostat as a separate issue from the ignition fault. [Elektroda, ondrei, post #16652930]

What was the factory coil brand observed on this engine family?

Users reported the original coil as TEMIC on a comparable 2.0, aligning with observations from the thread’s teardown. “The original is a TEMIC coil.” [Elektroda, grala1, post #16653774]

How do I pick a replacement coil if catalogs list only “ignition coil”?

Choose a unit specified for the AZJ engine code. The module is integrated, so listings may say “coil” or “coil module.” Brands cited were Beru and NGK. [Elektroda, sulof1601, post #16653081]

What are the telltale signs the coil itself is physically bad?

A visual crack on the coil body is a red flag. The reporting owner found a slight crack underneath; replacing it eliminated the jerking. [Elektroda, ondrei, post #16654938]

Can wet weather alone trigger these AZJ misfires?

Yes. The owner saw consistent jerking and power loss on damp or cold starts, clearing as temperature rose. That weather-linked pattern implicates ignition components. [Elektroda, ondrei, post #16652930]

How do I replace the AZJ coil? (3-step How-To)

  1. Remove secondary air pump for access; unplug its connector. Label each HV cable.
  2. Undo the three Torx screws; detach the coil connector.
  3. Fit the new coil, reconnect HV leads and plug; refit the pump. [Elektroda, ondrei, post #16659423]
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