[Huskymaniac]

Originally Posted by oab_au

If the fuel pressure regulator's sensor pipe has a leak in it ,then the fuel pressure will be higher, to all cylinders. The O2 sensors will then reduce the pulse width to reduce the fuel within its available range.

The IRIS opening will have no effect on the vacuum level that they work from.

Harvey.

What I was thinking was that a leak in the line to this nipple (the bend is quite harsh so it would be a candidate for a leak as the hose get dry and hard) would cause extra air to get sucked into the right side of the manifold. That extra air would eventually be detected downstream by the O2 sensor. Consequently, the ECU would increase the amount of fuel injected by the right side injectors (fuel trim) to maintain the desired ratio.

At high RPMs, the IRIS would be open and the extra air being sucked in through this leak would be divided by both banks. That should result in the fuel trim being increased on both banks but by a lesser amount. At low RPMs, the extra air would stay confined to the right side so only the right bank fuel trim would be increased.

The IRIS keeps the left side and right side of the intake manifold isolated at low RPMs, correct? If so, any air leak on either side should result in an increased fuel trim for that side only, at low RPMs. So the main question really is, where could there be a leak that would be isolated to either side at low RPMs?