FAQ
TL;DR: Suspect cylinder compression? Re-test before tearing down: “12 Atmospheres for all of them,” after a second check, resolved panic. [Elektroda, marekwodniak, post #16822216]
Why it matters: This FAQ helps Skoda Fabia 1.4 80 KM owners diagnose one-cylinder low compression and avoid costly missteps.
Quick Facts
- Reported oil use: ~0.8 L per 8,000 km; engine still felt strong. [Elektroda, marekwodniak, post #16811519]
- First reading mismatch: 3 cylinders >15 atm, 1 cylinder ~5.5 atm. [Elektroda, marekwodniak, post #16811519]
- Independent re-test: 12 atm on all cylinders; measurements must be verified. [Elektroda, marekwodniak, post #16822216]
- Dirty throttle body found; drivability improved after cleaning. [Elektroda, marekwodniak, post #16813574]
- Wet compression check: add oil to the low cylinder and retest. [Elektroda, jarek225, post #16812078]
What does “low compression on one cylinder” mean in this Fabia?
It means one cylinder seals poorly versus the others. The OP saw ~5.5 atm on one cylinder, while others exceeded 15 atm. That imbalance suggests leakage past rings, valves, or a head gasket. Confirm with a repeat test before deciding on repairs. [Elektroda, marekwodniak, post #16811519]
How do I confirm the compression reading is real?
Re-test with another mechanic and a known-good gauge. In this case, a second shop measured 12 atm uniformly and closed the issue. Always compare all cylinders and record results with the throttle wide open and a charged battery. “12 Atmospheres for all of them.” [Elektroda, marekwodniak, post #16822216]
How do I perform a wet compression test on this engine?
Do a dry test first. Then add a small amount of engine oil into the suspect cylinder through the spark plug hole and retest. If pressure rises, suspect ring sealing. If it does not, inspect valves or the head gasket next. 1. Dry test. 2. Add oil. 3. Re-test. [Elektroda, jarek225, post #16812078]
Is it rings, valves, or head gasket—how do I tell?
Start with wet compression. Rising pressure points to rings. No change points to valves or a head gasket. As one expert put it, “How can you be sure it’s rings, not valves, or a leaky gasket?” Use leak-down testing to localize. [Elektroda, DriverMSG, post #16811634]
What symptoms should I expect at ~5.5 atm on one cylinder?
Expect poor combustion on that cylinder. You may see misfires, a rough idle, and fault codes. An experienced member noted that with such pressure, combustion suffers, so misfires and uneven running are typical. Check plug condition to corroborate. [Elektroda, mario 77, post #16813648]
Can a clogged PCV (called “emphysema” here) or dirty throttle cause low compression?
A clogged crankcase vent or sticky throttle affects drivability, not true compression sealing. In this case, the throttle was dirty and cleaning helped response, but compression concerns persisted until re-testing showed normal values. Address both, but validate compression independently. [Elektroda, marekwodniak, post #16813574]
Is it safe to keep driving if one cylinder reads very low?
No. A veteran member warned that a cylinder with such a reading should not be working. Continued driving risks damage and unburned fuel issues. Verify with a second test before deciding, but do not ignore a grossly low value. [Elektroda, milejow, post #16814455]
My Fabia uses ~0.8 L per 8,000 km. Should I worry about the rings?
That consumption was reported alongside strong performance. Oil use alone did not prove ring failure in this thread. Use wet compression and leak-down to evaluate sealing rather than judging by oil consumption alone. Then monitor usage trend after maintenance. [Elektroda, marekwodniak, post #16811519]
Will inspecting spark plugs help locate the problem cylinder?
Yes. Remove plugs and compare deposits. An oil-fouled plug suggests ring or guide issues. A clean but wet plug suggests poor combustion. The thread notes that plug condition should reveal clues when compression is very low. Log photos before cleaning. [Elektroda, mario 77, post #16813648]
What compression numbers are considered healthy here?
A second shop measured 12 atm across all cylinders, which the community regarded as healthy. Use uniformity as your first criterion. Large spreads matter more than absolute numbers when sources conflict. Retest if results are inconsistent. [Elektroda, marekwodniak, post #16822216]
Why did two mechanics report 5.5–15+ atm first, then 12 atm later?
Measurement error happens. The OP suspected workshop handling or a faulty gauge. Poor procedure, a closed throttle, or a weak battery can also skew results. Always cross-check with another tool and technician before committing to repairs. [Elektroda, marekwodniak, post #16823015]
Does a high top speed prove my engine is fine?
No. Anecdotal top-speed runs do not replace diagnostics. One comment even mocked the claim of “almost 180 per hour.” Focus on uniform compression and drivability metrics, not brief highway tests. Use data, not speed tests, to decide. [Elektroda, servicemen, post #16823456]
