Fuel Pumps and O2 sensor
 

As some of you know, we have installed a 1995 C36 Engine, tranny, diff
(2.87) and engine computer (ABS and EA is a 1995 E320 wagon), into a
1988 300TE wagon.

I was experiencing intermittant CHECK ENGINE lights and the codes were
pointing to a LEAN CONDITION.
Since we had retained the original two fuel pumps from the CIS M103, I
decided to change the fuel-filter, thinking it may have an obstruction.

After changing the fuel-filter I have gone approx. 3-months without any
CHECK ENGINE lights.

Just two weeks ago, I decided to change to a 3.07 limited-slip rear
differential. And the next day, I got a CHECK ENGINE light while going
through stop-n-go traffic in 2nd gear. An OBDII scan showed two codes:
P1132- Manufacture controlled Fuel & Air Metering; and
P0134 02 Sensor Circuit No Activity Detected, Bank 1, Sensor 1.

We checked the O2 sensor, with a VOM and it tested good.
Cleared CODE.
3-days later on a 5-hour drive to San Francisco at a steady 80MPH, the
CHECK ENGINE light comes on.
Same codes. CLEARED it. My mechanic hooked-up a fuel-pressure gauge and
I drove for about 30-minutes, up long grades at full-throttle, just to
see if the two CIS fuel-pumps were either giving too much pressure or
not enough. Pressure was 48PSI at idle at upto to 58 PSI at full
throttle with a long load. CHECK ENGINE did not come on.

However, on a short drive 15-minute drive, the CHECK ENGINE came on.
Same CODES.

What to do?

Do I just change out the front O2-sensor? It's a 4-wire one, will any
BOSCH 4-wire work, or do I have to use the Mercedes specific front
O2-sensor at almost 3-times the price?

Should I change out the twin CIS fuel-pumps, and go to the single high
volume, low-pressue fuel-pump of the stock C36?

Should I clean out the MAS sensor?

Any other ideas?

Thanks in advance,
:-) neil
1988 360TE AMG