FAQ
TL;DR: 11.7–12.3 bar compression was logged; “after unplugging the injection plug the engine operation does not change.” For Golf 4 1.6 SR owners with a 3‑cylinder misfire, check ignition first, then oil‑fouled plugs, rings, and valves. [Elektroda, thepantis, post #17393686]
Why it matters: Catching a dead cylinder early prevents costly escalation from fouled plugs to ring and head repairs.
Quick Facts
- Reported fuel use rose to ~17–18 l/100 km during the fault; strong fuel smell noted. [Elektroda, thepantis, post #17392195]
- Case compression measured 11.7–12.3 bar across all four cylinders. [Elektroda, thepantis, post #17393686]
- This engine uses a double coil; cylinders 2 and 3 fire together. [Elektroda, marszałekkom, #17400967]
- Oil‑fouled plugs here produced no spark until replaced/repair. [Elektroda, thepantis, post #18507410]
- Final fix reported: piston rings, cylinder honing, and head repair. [Elektroda, thepantis, post #18507410]
What are the likely causes of a 3‑cylinder misfire on a Golf 4 1.6 SR?
Start with ignition. When compression looks even, the coil pack is a prime suspect. One expert said, “Replace the coil.” Test with a known‑good coil before chasing fuel or mechanical causes. Inspect leads and plugs during the same session. [Elektroda, robokop, post #17392221]
I unplugged the injector on the bad cylinder and nothing changed. Is that normal?
Yes. If a cylinder is already non‑contributing, removing its fuel won’t alter engine behavior. As noted: “Why should it change if the cylinder is not working?” Use this to confirm a dead pot, then test spark, fuel, and compression systematically. [Elektroda, robokop, post #17399125]
Are 11.7–12.3 bar compression readings acceptable in this case?
Those were the reported values across all four cylinders in the thread. The even spread suggests nothing singled out mechanically during that test. The fault source was elsewhere in the chain for that vehicle. Compare cylinders first, then proceed. [Elektroda, thepantis, post #17393686]
How can I tell if worn rings or valve seals/guides are causing oil on the plug?
Run a dry compression test, then add a teaspoon of oil and repeat (wet test). A large rise indicates worn rings. Little or no change points at valves or valve seals/guides. This helps decide head work versus bottom‑end work. [Haynes, 2021]
I see spark outside, yet the cylinder still misfires under load—why?
A spark that jumps in air can fail under cylinder pressure. “Candles give a spark but in the air, inside the cylinder may be too weak or not at all.” Cylinders 2 and 3 also fire together, complicating tracing. [Elektroda, marszałekkom, #17400967]
How do I isolate an ignition issue between cylinders 2 and 3?
Use this quick How‑To:
- Identify which cylinder is not contributing at idle.
- Swap the ignition cable plugs for cylinders 2 and 3 on the coil.
- If the misfire moves, the fault is in the swapped path (lead/plug/connection). [Elektroda, marszałekkom, #17400967]
Could a leaking injector be the cause, and how do I check it?
Yes. Swap the suspect injector with one from a good cylinder. If the misfire follows the injector, it’s likely leaking or stuck. If not, refocus on ignition or mechanical causes. “Change the injection places – maybe the injection is pouring?” [Elektroda, janusz ford 1976, #17400998]
VAG/VCDS shows no spark or misfire errors. Can a cylinder still be dead?
Yes. The OP reported no VAG errors, yet unplugging injector 2 did not change operation. Use scan data plus simple isolation tests to confirm a dead cylinder before deeper teardown. [Elektroda, thepantis, post #17393686]
Why did fuel consumption jump to ~17–18 l/100 km during the fault?
A dead cylinder wastes injected fuel because it does not burn it. In the case reported, consumption rose to about 17–18 l/100 km with a strong fuel smell. Restore combustion on all cylinders to normalize economy. [Elektroda, thepantis, post #17392195]
What does gasoline mixed with engine oil indicate in this scenario?
The OP found fuel in the oil and a temporarily clean plug. Soon after, cylinder 2’s plug re‑fouled like “mud,” returning within 2–3 km after cleaning. Treat fuel‑diluted oil as a red flag and investigate root mechanical causes. [Elektroda, thepantis, post #17429429]
What ultimately solved the 3‑cylinder issue in the thread?
Mechanical repair: new piston rings, cylinder honing, and cylinder head work. Oil‑carbon‑fouled plugs had no spark until the root cause was fixed. After repair, the engine ran correctly. [Elektroda, thepantis, post #18507410]
Is replacing only valve stem seals likely to fix oil fouling here?
Unlikely. “Do not count on replacing the sealants on the guides and it will be good.” The advice was to remove the head, measure guides, and rework seats, or consider another engine if wear is severe. [Elektroda, grala1, post #17430576]
Can an oil‑fouled plug really cause “no spark” under compression?
Yes. The final update confirms oil‑carbon‑fouled plugs produced no spark and killed the cylinder. Replace fouled plugs only after fixing the cause, or the misfire returns quickly. [Elektroda, thepantis, post #18507410]
picture from the internet, the candle is like this one in the middle but I have 3 electrodes.
