Poor Performance, Excessive Smoke, Misfire, Cuts Out

07.1-87011 Poor Engine Performance After Cold Start Engine 603 1/87
with Excessive Exhaust Smoke, Misfiring
Engine Cuts Out

Cause:
This condition can be caused if the electrical connectors or vacuum lines on the air recirculating valve vacuum transducer (Y31) and the EGR valve vacuum transducer Y31/1) are interchanged.

Note:
Since the wiring harness for the 1886 model 126.125 in both Federal and California versions is identical, the wrong hookup is also possible on 1886 Federal vehicles where the lead to the non existing air recirculating valve vacuum transducer (Y31) is taped back onto the wiring harness.

Remedy:
The following test can be performed to verify correct hookup of the electrical connectors

Connect vacuum gauge with Y-connector to EGR valve. With coolant temperature below 40° C (or disconnecting of coolant temperature sensor and connect 2.5 k Ohm resistance between plug and ground), start engine, increase engine rpm to approx. 1200 rpm and read vacuum gauge. The vacuum should not exceed 50 mbar and the EGR valve remains closed. If vacuum is above 200 mbar, check and correct electrical connectors or vacuum lines on vacuum transducers.

EGR valve vacuum transducer (Y31/1) = red/yellow and brown/purple wire
Air recirculating valve vacuum transducer Y31) = red/yellow and brown/gray wire.