My work's Peugeot 107 5-speed manual is running on 2 cylinders instead of 3. I know this because it produces noticeably less power than a Toyota Aygo that I drive occasionally that has the same 998cc 1KR-FE engine. Also it sounds different than the Aygo's engine, and the engine is shaking more than normal.

I know that the car has driven with a low oil level, because I noticed the oil warning light came on occasionally when driving in corners and when braking. (Probably because of oil sloshing around). I ended up adding about 2 liters, now the oil level is right on the max.

When looking for common issues with this car, I only found a rough idling engine to be a common fault, but this isn't really my problem. When idling, the car remains at the same RPM. I couldn't find any other engine related common faults, so my guess is that this issue has to do with the low oil level it has been driving with. Is this a reasonable assumption or should I be looking elsewhere? And what should I be looking at?

Does anyone have experience with this car or had similar issues and what was the cause? Any help appreciated!

UPDATE (7 december 2020): I haven't had the chance to look at the spark plugs, because the car has developed more issues: the clutch is broken; the pedal feels weird and it won't disengage the clutch. Also it's impossible to put it in gear. The car will be towed to a garage, where the issues will either be fixed, or the car will be scraped. Depending on the costs of the repairs.

  • Please check the spark plugs (both picture and gap) and post photos. Is there a check engine light?
    – Martin
    Commented Dec 2, 2020 at 15:58
  • @Martin there's no check engine light. Also, if I just put in a new spark plug and it still doesn't work, can I assume that the problem is not caused by a faulty spark plug?
    – user60481
    Commented Dec 2, 2020 at 16:47
  • I once had an old 3 cylinder. Once it drove exceptionally rough (and with low power). Turns out one spark plug was consumed
    – Martin
    Commented Dec 2, 2020 at 16:47
  • When there is only one non-working cylinder I'd assume some spark-related or injector related fault. A look at the spark plugs would be interesting. Perhaps remove all the plugs immedeatly after a short run: With a bit of luck one is cold and smells of unburned fuel ->sparkplug/coil/cable problem. One plug having a distinctive color could also be revealing
    – Martin
    Commented Dec 2, 2020 at 16:54
  • Do a Morse test.
    – Solar Mike
    Commented Dec 2, 2020 at 21:18

1 Answer 1


Low oil might potentially damage an engine so badly that there is a loss of power. In such an unlikely case, there will be blue smoke coming from the tailpipe due to warn cylinders and poor compression. I did have a car with this condition, years ago, but the loss of power was slight and the bigger issue was loud ping (detonation) on the highway. In your case, there would be a "check engine" light.

If the car has been burning some oil over time, the engine probably has carbon deposits that will lose power and create rough idle. How did the spark plugs look when you replaced them? If blackened, carbon is definitely an issue.

Cleaning carbon can be difficult. Start by changing the crankcase oil, substituting 20% with automatic transmission fluid (ATF) for 500 km and then changing the oil and filter again. Also add ATF to the fuel tank at a treat rate of 8 ml per one liter of gas and drive the car aggressively for one tankful. If power returns noticeably, continue to use your favorite fuel injector cleaner in the gas for a few more tankfuls. For faster results, spray cleaner slowly through the induction tubing at high idle.

  • Thank you for your answer! But I don't understand the benefit of adding ATF to the fuel. Could you please explain?
    – user60481
    Commented Dec 7, 2020 at 8:59
  • ATF, as a rich blend of medium viscosity oils, has properties of both a hydraulic fluid and a motor oil that penetrates gum and carbon, is highly refined, and thus burns cleanly. When added to fuel, it breaks down power robbing deposits in filters, injectors, intake valve stems & seats, heads, spark plugs, pistons and piston rings. It even works its way into the exhaust, cleaning exhaust valve stems & EGR valves. It lubricates and frees stuck injector pintles, valve guides, top piston rings. Always use 2 ml/litre on a new car as a preventive measure. Combine with solvent for fast cleaning
    – Carguy
    Commented Dec 7, 2020 at 10:37
  • ATF is most effective at high heat and pressure. Drive aggressively after adding a large dose to the fuel, particularly at highway speeds. I've had best results in hot summer, combining ATF with Liqui Moly Ventil Sauber (also at a treat rate of 8 ml/litre). Will never harm the engine internals, so don't be afraid to add ATF to the crankcase for cleaning and enhanced lubrication, especially in winter months. I've used it on many cars over many years, including late model, Mercedes Benz, high compression engines.
    – Carguy
    Commented Dec 7, 2020 at 10:51
  • Lastly, ATF contains no sulfur or heavy metals, so it will not damage O2 sensors or catalytic converters.
    – Carguy
    Commented Dec 7, 2020 at 10:59

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