So I finally got a test pipe made and installed a full 3" turbo-back exhaust (except for the 2.5" bend coming off the turbo on the Roush kit). Now that the cat is gone, I was able to install the AEM UEGO wide-band that I've had sitting around for awhile. The O2 sensor sits practically under the engine to guarantee the 36" from the exhaust port that the installation manual dictates. Before I installed the whole new exhaust, I tried putting the wide-band O2 in the bung that comes on the Roush 90 degree bend, but it was giving sporadic readings so I just removed it as that was maybe 6 inches from the exhaust port, not the required 36.
Now for the problem, or what I suspect is a problem. At idle, the AFR will fluctuate between 13.5 and 15.5. Occasionally, it will spike to 17+ then return back to fluctuating. The engine also feels like it's quite sure where to idle. It's still relatively smooth, or as smooth as it can be with all three VF motor mounts. While cruising, if I let off the throttle the AFR will usually peg lean like I would expect, but every so often it'll lean out, then become very rich (12-13) while engine braking. Sometimes it stays rich at idle, too.
I originally thought this may be a vacuum leak, but my vacuum is rock steady at idle.
While in boost, everything appears fine. I see 10.5-11.5 under full boost (~8 PSI).
Any ideas what could be causing this? Could a bad upstream O2 be a culprit?
Also, for those of you running with no cat and just a resonator and/or straight-through muffler, is it common to get some fairly loud popping coming from the exhaust while coasting around 2k RPM?
Thanks!
Now for the problem, or what I suspect is a problem. At idle, the AFR will fluctuate between 13.5 and 15.5. Occasionally, it will spike to 17+ then return back to fluctuating. The engine also feels like it's quite sure where to idle. It's still relatively smooth, or as smooth as it can be with all three VF motor mounts. While cruising, if I let off the throttle the AFR will usually peg lean like I would expect, but every so often it'll lean out, then become very rich (12-13) while engine braking. Sometimes it stays rich at idle, too.
I originally thought this may be a vacuum leak, but my vacuum is rock steady at idle.
While in boost, everything appears fine. I see 10.5-11.5 under full boost (~8 PSI).
Any ideas what could be causing this? Could a bad upstream O2 be a culprit?
Also, for those of you running with no cat and just a resonator and/or straight-through muffler, is it common to get some fairly loud popping coming from the exhaust while coasting around 2k RPM?
Thanks!