Interesting development with the S12

[Nattman82]

So, since I got the car on the road ive been having this really annoying flat spot issue at motorway cruising speeds. Its also evident driving around town as the revs reach and pass between 2500rpm and 3000rpm. My first thoughts was something on the ignition breaking down but under hard acceleration it ran spot on. Anyway after much headscratching and changing of parts from a mates S12 I was none the wiser....untill yesterday. Driving home the flat spot was really bad (that was the other problem, it was very erratic, sometimes bad sometimes not) so I pulled over to rage a bit at the car, and in doing so managed to knock the ECU down from under the dash. FFS. So thought f**k it and started to drive home...... and hey presto.....car ran like a dream, flat spot completely gone. So I pulled over again and put the ECU back up, drove away and it rears its ugly head again, same again pulled over and dropped the ECU down and its gone.

So im happy that I have found what appears to be the issue but not so happy as it looks as though I have a wiring issue between the ECu and whatever component of the engine. Im happy just to secure the ECU on the floor for the time being as its only ever me in the car but I can foresee a long and lengthy process of tracing the fault and dealing with it. Still, least she drives much better now.