Hi all,

After replacing the exhaust system from the catalytic converter back, and from the engine to the catalytic back, my 1991 240 began running terribly rich on fuel. The problem started after having difficulty starting the car. Initially, we thought the problem might be related to spraying the engine with cold water to clean it, but now we aren't so sure. Initially, we got codes 1-1-3, 2-3-1, 2-3-2, 2-2-1 (in that order)

A list of what we've done:

-Checked the spark plugs, which were covered in carbon
-Took the air intake hose off, but found no splints.
Cleaned and changed Air Massmeter
-installed new exhaust manifold gaskets
-new header pipe gaskets
-New cat. converter gasket
-Tested fuel pressure
-Fuel rail with injectors on test pump (spray pattern on two of them were not the best, replaced #4 upon seeing 1-2KV compared to 3-7 KV of others)
-Looked for vacuum leaks but found none

The car started running on higher RPM's. Pinched off idle air control hose to air intake, slowed down, let go. RPMs came down to around 800.

-Sprayed intake cleaner in vacuum port on throttle body while running
-Tested 02 sensor using voltmeter; inducing lean condition by pulling off small vacuum line and rich condition by pulling off vacuum hose off fuel pressure regulator. Saw hardly any change.
-Installed new bosch 13034 o2 sensor, numbers moved significantly when lean/rich situations were induced.

At this point, the only codes that are appearing are 2-3-1 and 2-2-1. Car would not have codes appear at idle, just when throttle was engaged.

After getting codes again, we tried a new series of tests

-Checked distributor shaft slop. Tested fine.
-replaced Dist. cap/rotor with new Bosch ones
-Replaced spark plugs with new Bosch Platinum Plus 4016
-Replaced sparkplug and coil wires with new Bosch 09231 wires.
-Checked fuel fuse #4 which is supposed to go to heater on 02 sensor - tested fine
-Took apart every electrical connector and used CRC QD cleaner, sprayed silicone on all connectors


The codes still exist, car runs a little bit rough with obvious rich fuel consumption.

Does anyone have any leads? We are at a bit of a loss of what to do next