Robert Rogers

I've searched and searched. This is such a common question, but I haven't found a definitive answer.

I google'd this question and found different gap settings for different plugs.

Bosch Plat - 1mm
Delco Regular - 1mm
Denso Iridium - .04
NGK IX .039

I have an 2001 e430 with 101k miles. Sometimes it starts to misfire and all I do is shut the engine off for a few seconds and back on and it runs fine for 20-30 miles before misfiring again.

So I thought I'd start with changing the plugs. I bought ngk iridium ix with .039 gap. I have a gap tool and need to know if .039 is correct or do I need to change it to 1mm, .04mm or something else.

Thanks.

lkchris

You have two metric measurements and two inch measurements and they're all the same.

Start off by considering changing your crankshaft position sensor.

Robert Rogers

Thanks for clearing that up for me. I feel like an idiot. Position sensor, eh? That sounds reasonable. I can see where that could cause the intermittent misfire. It's not something that would show up in the obdii? I only get misfire codes. I'll look around and see what comes up online about that.

I really appreciate the advice.