4E-Fe - Do Spark Plugs Have To Be Resistance Ones?

December 11, 2010

Just changed the spark plugs on my GF's 1998 EP91 Starlet Sol with 4E-FE engine, fitting Bosch FR78 super 4 plugs, which Bosch specify as suitable for this engine. Just noticed the ones that came out are Denso K16R-U (guessing these are the ones used by Toyota themselves). A quick google reveals these to be resistor spark plugs, and a further google gives dire warnings (quoted below) as to what might happen if you use non-resistor plugs in an engine that specifies them. A further google finds no mention of the Bosch FR78 Super 4 plugs being resistance spark plugs. I was just wondering if I now need to rush out to buy some resistor spark plugs. Thanks in advance.

As well as reducing electrical noise for radio, television and mobile telephones etc, many modern ignition systems require resistor plugs to stop electrical noise from interfering with the vehicle's on-board electronic control units (ECUs). If non-resistor plugs are used in place of resistor ones, the result can be malfunction and in some cases immobilisation of the vehicle. Resistor spark plugs should always be fitted, therefore, where specified. NGK resistor spark plugs contain a single ceramic monolythic resistor of approximately 5000 ohms. Because of the type and construction of the resistor (ie no springs), the problems of vibration and sudden changes in temperature that can occur with some other brands do not apply. The function of the resistor is to reduce electrical noise generated by the ignition system. The most effective place to situate a resistor in the high tension circuit is as close to the spark plug as possible. This makes the spark plug an ideal place to house the resistor. Because the resistance value is only approximately 5000 ohms, there is no detrimental effect on engine performance, power output, vehicle emissions etc. It is also a fact that many motor sport world champions only use NGK resistor spark plugs. In nearly all cases - apart from some very old low output ignition systems - resistor spark plugs can be used in place of the non resistor versions

Edit: just had a brain wave, the "R" in FR78 I presume could be suggesting it is a resistor plug? I have now read that apparently most plugs are now resistor ones.