Understand how the gap affects engine performance. This basic guide is designed to assist the technician, hobbyist or race technician in understanding, using and troubleshooting spark plugs. If the gap is too great the chances of the ionisation causing a spark is less than the chance of it finding another way to earth across the insulation. A gap that is too wide might prevent a spark from firing at all or may misfire at high speeds, but will usually have a spark that is strong for a clean burn. Excessive plug gap also results in cylinder misfiring, a possible no-start condition, wet, black or fouled plugs, engine hesitation and rough idle. If the gap is too small, there isn't enough room for enough of the air/fuel mixture to get between the electrode and ground strap, so when the plug does fire there is a chance nothing will ignite. Adnan ferozi on December 02, 2018: If the gap is too large, the plug may not fire at all. If it’s too small, there may not be enough of a spark to ignite the air-fuel mixture. Being as this didn't affect performance, I though I'd leave it as that. Decreasing the gap can make it vulnerable to incomplete burn or misfire. Excessive plug gap also results in cylinder misfiring, a possible no-start condition, wet, black or fouled plugs, engine hesitation and rough idle. Hi My Escort has an HCS engine with carburettor. Utilize gap-closing tools when gaps are too large. Spark plugs are often very cheap and, in most cases, easy to replace. Replacing the spark plugs will do the trick as well. Small engines typically require a spark plug gap … The spark gap is much wider than a typical J-gap plug (up to 3 mm) so a surface gap plug requires much higher firing voltages and a high performance ignition system that can generate a lot of juice. The spark plug will come out of the factory at a stock gap specification, and your engine may also have a recommended specification that is different than the spark plug that is recommended. Excessive spark plug gap also happens as result of … Excessive spark plug gap results when the voltage has too far to travel. Increase or decrease the size of the gap as needed based on engine manufacturer recommendations. Data block 14,15,16 group shows total of 134 times, 3 cylinder misfire of 134 times in stable misfire condition. A: If you don’t gap your spark plugs or gap them incorrectly, the gap may be too wide for a spark to ignite, it could skip the spark entirely, or it could ignite the fuel/air mixture too soon causing a rough idle or misfire. If so you can lift the side electrode with a pliers. Either scenario can cause a misfire that can damage your car’s inner workings. A narrow gap may give too small and weak a spark to effectively ignite the fuel-air mixture, but the plug will almost always fire on each cycle. It may be convenient to have an extra spark plug handy so you can try replacing the plug altogether to be sure if a faulty spark plug is causing the engine to misfire. too small might run oddly, but too large will fail to spark at high load, which does really interesting(bad) things to your secondary ignition, along with falsely triggering the knock sensor most of the time. Just a suggestion to inspect the spark plug and verify that the center electrode is not making contact with the side electrode as they need to have a small gap in between. Getting the best gap between the points is essential for proper engine performance and reliability. Too small, and they can get lodged into the seams of the spark plug." Setting the Point Gap . When a engine has forced induction, aka *(turbocharger,supercharger or blower) it increases the cylinder pressure and can cause the spark to blow out when the spark plug gap is too big. The next step is to measure the spark plug gap. Virtually all NGK spark plugs are set to the correct gap for the catalogue applications at the point of manufacture'. However, when the garage fitted new plugs (champion copper core/electrode), they didn't adjust their gap and left them at 0.8mm. If you try a new spark plug and continue to have the same issue with your engine, the problem is likely coming from a different component. All engine manufacturers publish specifications for spark plug gap in owner's manuals and online. Check the gap on all spark plugs, even ones that claim to be pre-gapped. If the recommended gap is too small the weak spark will cause poor running and poor efficiency. Likewise, if the tool doesn’t fit between the electrodes the gap is too small. The gap is pre-determined by the manufacturer and it is measured in millimeters. Why gap … Also, always check the spark plug gap and set it to the correct specs. Spark gap and voltage requirements are determined mostly by compression, air/fuel mixture, and fuel type. What is my lawn mower spark plug gap? Q: What Happens If Your Spark Plug Gaps Are Too Small? The second most common cause of a misfire is bad spark plugs. How to Know Spark Plugs Aren’t Too Loose or Too Tight? The spark is made by ionisation of the gases in the combustion chamber. Either way, a spark which only intermittently fails to ignite the fuel-air mixture may not be noticeable directly, but will show up as a reduction in the engine's power and fuel efficiency. If you can’t remember the last time you replaced your spark plugs, it’s probably time to replace them. A fully-functioning spark plug helps burn fuel efficiently in the combustion cycle. The symptom can occur due to too big or too small a gap between the electrode and the central piece on a spark plug. 1990 LX Convertible Triple Black Coyote Whippled Corroded spark plugs can often be cleaned. Spark plug gap too small? When spark plugs are replaced, the gap is checked and altered if necessary. I very much doubt the spark plug gap would be causing issues like that mate, start looking elsewhere . If they’re too loose, you may be able to turn it with your fingers. If you have no spark and your trigger tests ok, your stator tests ok and you have tried a new set of coils then we’re possibly looking at a bad CDI box. a gap too small is preferable to a gap that is too big. If the gap is too small, the spark will likely be too weak and cause the engine to run poorly or with poor efficiency. Test the width of the gap using a spark plug gap tool. Excessive spark plug gap results when the voltage has too far to travel. I have a premium Lisle spark plug gapper & feeler gauge set and made in the USA, and I never had a problem with it. How to gap a spark plug. Spark plugs with the gap set too small on them can make the motor run poorly. The gap must be a specific width if the gap is too small the spark doesn’t have enough space to generate the power needed to ignite the fuel. Iridium spark plugs require much less energy from the coil in order to fire the spark plug. If your spark plugs aren’t properly gapped, your engine may not burn fuel properly. Use a ramp-style gauge when necessary. Spark Plug Basics. Spark plugs that do not have the proper gap lead to premature wear, ignition system stress, and even cylinder misfires. Since every make and model requires a different gap size, start by looking in the owner’s manual for your vehicle to find the required gap size, or pull the information up online. If the gap is too wide the ignition system components are required to work harder to jump across the extended gap leading to spark plug, ignition coil, and control module failures. This cause my 250 cc dirt bike to misfire after i changed the spark plug. 1,721 Posts . You’ll need to go to the manufacturer’s website or read the manual to see the exact gap in your lawnmower spark plug. Discussion Starter • #1 • Jan 7, 2011. will a spark plug gap that is too narrow cause the engine to misfire? Does the OE require iridium plugs? Too small of a spark plug gap can cause the engine to run rough and have inconsistent rpm's. As a test, you can try closing the gap to about 0.030 and see if you notice a difference. A spark plug gap is the distance between the end of the electrode and the base of the spark plug. An increased gap requires increased voltage and amperage in order to maintain spark density. The spark plugs fire up your cylinders, and they can get worn over time. Do all spark plugs … Each car has a different value so you will need a tool to measure that gap and adjust it.