Reading plugs in EFI engines isn't much help. The EFI runs lean in every mode to keep down emissions except full power. Make a full power run, slow down to pull over to the side of the road to read the plugs. When you do that, the computer trims back fuel to the 14.7:1 or leaner A/F point. Now the plugs show the results of the 14.7:1 or leaner A/F that the engine was running just before you shut it off at roadside.
The only way to get any useful reading is to turn off the ignition while at full power, put the trans in neutral and coast to the side of the road. Even then you may not get any useful information from trying to read the plugs.
Reading plugs in EFI engines isn't much help. The EFI runs lean in every mode to keep down emissions except full power. Make a full power run, slow down to pull over to the side of the road to read the plugs. When you do that, the computer trims back fuel to the 14.7:1 or leaner A/F point. Now the plugs show the results of the 14.7:1 or leaner A/F that the engine was running just before you shut it off at roadside.
The only way to get any useful reading is to turn off the ignition while at full power, put the trans in neutral and coast to the side of the road. Even then you may not get any useful information from trying to read the plugs.
Reading plugs in EFI engines isn't much help. The EFI runs lean in every mode to keep down emissions except full power. Make a full power run, slow down to pull over to the side of the road to read the plugs. When you do that, the computer trims back fuel to the 14.7:1 or leaner A/F point. Now the plugs show the results of the 14.7:1 or leaner A/F that the engine was running just before you shut it off at roadside.
The only way to get any useful reading is to turn off the ignition while at full power, put the trans in neutral and coast to the side of the road. Even then you may not get any useful information from trying to read the plugs.
I disagree- espcially if you have a power adder, it is very important to read the plugs. You can detect detonation, fouling, and other issues. If you see any speckling, see it is whitewashed, or worse, then that can help diagnose problems.
I disagree- espcially if you have a power adder, it is very important to read the plugs. You can detect detonation, fouling, and other issues. If you see any speckling, see it is whitewashed, or worse, then that can help diagnose problems.
The only way to get useful information from reading spark plugs is to drive the car at high load/high RPM and then turn the ignition off, put the transmission in neutral and coast to the side of the road. Then pull the spark plugs and attempt to read them.
The problem is that most guys will just decide to pull the plugs for inspection while the car is sitting in the garage doing nothing. Then what they observe is the average of all the conditions that the engine has been subject to over a period of time. Most evidence is obscured by the overlaying of "average operation" on any evidence of stress induced signs of problems. It's a lot like trying to determine what color the car was originally after it has been repainted several times with different colors of paint.
Obvious hard failures, like oil fouling, coolant leaking into the combustion chamber, and fuel injector stuck open can be spotted by a casual inspection. However, by this point, the engine isn't performing to the point that it is noticeable to the observant driver.