Hey guys, Strange problem encountered at the lights this morning. Was idling fine, but then all of a sudden the engine began stumbling and missing to the point of almost stalling. Interestingly, o2 readings only seemed to be affected on one side of the bank while this was happening. Throttle bodies were closed and vacuum gauge read normal so I don't think it was a leak. Would a faulty o2 sensor cause this? My first thought was no because I was under the impression they didn't kick in until over 2k rpms. But if the sensor is malfunctioning could this cause one bank to run rich and stumble? CAS and TPS readings are fine, series 2 ptu, no error codes. Problem went away soon after I took off and I cannot recreate the symptoms at the moment - o2's reading normally again. I will unplug them if it occurs again and see if that fixes it. Any thoughts on what it could be? Cheers, Martin
No idea, but interested in what you find out. Mine's done that every now and again. Give it a good rev and it settles down. Wierd.
You've got it the wrong way 'round - 02's do nothing over 3000 RPM. It's below that they operate. Doubt it'd be an 02 though. I had two dead 02's for months on my NA and it just meant a slightly raise idle and bad fuel consumption.
Thanks for the suggestions guys, my idle is actually controlled by a garden irrigation hose pressure fitting so fully manual - running over 1 year with no probs. Appreciate the clarification re: o2's and revs - I can't help but feel my problem lies there. I know that when they're dead/off they'll sit on 32. At the lights I saw one side reading about 70, would this not cause the symptoms I observed? For reference, I also have BOV's but don't believe they are at fault..
Faulty coil pack. O2 would report fully rich when it happens. Rev it a bit and the coil comes alive again.
Thanks Stef, got spares so will check it out! It was definately more than just a miss on one cylinder though, felt like it was only running on three..
Hey peeps, thanks for the suggestions! I think I have fixed the issue and it seems it was the BOVs. It seemed to occur just after high vaccuum during decelleration or cruising with light throttle. Over time one of the BOVs appear to have lost their smooth operation and become slightly 'sticky'. Kept one of them open slightly thus leaking boost which was why one side was affected and causing extremely rich running/stumbling. I have since cleaned and re-greased the piston and increased spring tension, now the car pulls much harder and is running like a champ! Cheers guys
