1999 S70 AWD (FWD only) Sudden Rough running. [bad coil/plug and Dead original ETM at 100k/28 years] Topic is solved

Post by **abscate** » 29 Jul 2026, 08:25

THis one of the Great Mysteries of Life - why does a failing ETM cause a cylinder 3-4-5 no fire?

Post by **bmdubya1198** » 29 Jul 2026, 08:51

abscate wrote: 29 Jul 2026, 08:25 THis one of the Great Mysteries of Life - why does a failing ETM cause a cylinder 3-4-5 no fire?

That is a really interesting detail about this one... that it specifically causes 3-5 to misfire but not 1-2.

Post by **abscate** » 29 Jul 2026, 08:59

I am guessing the ETM fails hard closed, and only the nearest runners (1-2

) get enough air to fire. But that should mean 3-4-5 run under vacuum and the brake booster vacuum also fails.

What system would you look for given the symptoms below?