E.Chambers
Member
2005 Mazda 3 2.0L, 43,000 miles.
Regularly maintained, no serious problems.
A few months back I installed a header+exhaust. The downstream o2 sensor was relocated behind a high-flow cat while the upstream sensor got replaced during the install due to some thread damage incurred. All went well besides that, no CEL or anything as far as that goes.
I've noticed since the mods that the RPMs like to dip while stopped at a red light, or if I leave it in N or P for a few minutes. What happens is it drops from the usual 750 or so to maybe around 4-500, shudders a bit, then goes back to around 750. It will repeat itself over and over if stopped long enough. From a cold start, the RPMs generally jump and stay up around 1500 momentarily, while if the engine is already warm it generally doesn't.
My best guess right now is that when the engine runs in closed loop mode, the fuel mixture is leaning out too much, then fixing itself. Repeatedly if left idling long enough.
So my question is what (if anything) can I do to solve the problem? I've thought about replacing both o2 sensors, but that is a fairly costly little repair for not being sure it will fix the issue.
Thanks for any help.
Regularly maintained, no serious problems.
A few months back I installed a header+exhaust. The downstream o2 sensor was relocated behind a high-flow cat while the upstream sensor got replaced during the install due to some thread damage incurred. All went well besides that, no CEL or anything as far as that goes.
I've noticed since the mods that the RPMs like to dip while stopped at a red light, or if I leave it in N or P for a few minutes. What happens is it drops from the usual 750 or so to maybe around 4-500, shudders a bit, then goes back to around 750. It will repeat itself over and over if stopped long enough. From a cold start, the RPMs generally jump and stay up around 1500 momentarily, while if the engine is already warm it generally doesn't.
My best guess right now is that when the engine runs in closed loop mode, the fuel mixture is leaning out too much, then fixing itself. Repeatedly if left idling long enough.
So my question is what (if anything) can I do to solve the problem? I've thought about replacing both o2 sensors, but that is a fairly costly little repair for not being sure it will fix the issue.
Thanks for any help.
