Engine - Long Cranking/Poor Warmup Performance

91audi05

Group: 25

Number: 91-09

Date: July 31, 1991


Subject: Engine cold: Long cranking/Poor running w/ambient temp. 45 to 65~F

Models: 80 and 90 w/Engine Code 3A m.y.1988-1990





Conditions:

^ ambient temperature between 45 and 65~F
^ excessive cranking time
^ poor performance during warmup

Note

This modification replaces the production cylinder head coolant flange with a new flange that includes the addition of a temperature switch. This arrangement provides optimum cold start enrichment during a difficult ambient temperature range for the engine management system.


CAUTION

For this procedure to be effective it is essential that the engine be optimally tuned and meet ALL running specifications. See Repair Manual Groups 25 and 28 for additional information.





^ carefully clamp off upper radiator hose approx. 12 in. from coolant flange
^ to minimize coolant loss during modification

^ carefully clamp off water pump hose approx. 6 in. from coolant flange
^ to minimize coolant loss during modification

^ disconnect coolant temperature sensor harness connector (to ECU) from sensor on bottom of flange
^ disconnect coolant temperature sensor harness connector (to gauge) from sensor on top of flange
^ loosen hose clamps and remove hoses from coolant flange





WARNING

Antifreeze can harm the environment. Carefully contain all drainage and dispose of properly.

^ remove coolant flange from cylinder head

Note

Some vehicles may have a plastic flange installed. The modification flange for ALL vehicles is metal.

^ remove temperature sensor from bottom of old coolant flange and install in bottom of new flange using new sealing washer
^ remove temperature sensor from top of old coolant flange and install in same top location of new flange using new sealing washer

^ install new temperature switch/sealing washer in new flange
^ top side, threaded hole nearest to cylinder head

^ attach new coolant flange assembly to cylinder head using new O-ring
^ 10 N-m (7 ft.lb.)

^ connect coolant hoses to flange and tighten clamps
^ release clamping tools from coolant hoses





^ install wiring adaptor harness as follows:
^ join adaptor connectors A to temperature switch (not polarized)
^ join adaptor connector B to lower temperature sensor (to ECU)
^ join adaptor connector C to vehicle harness connector that was previously attached to lower temperature sensor (to ECU)
^ reconnect exisfing harness connector (as before) to coolant temperature sensor (to gauge) on top of coolant flange (not shown in illustration)





^ neatly tie wrap any loose adaptor wires to the upper radiator hose
^ leave enough slack in wiring to provide for engine movement

^ top up coolant as necessary
^ start engine and run until cooling fan comes on at least once
^ check coolant again and adjust level as necessary


Parts required:

Adaptor harness 893 971 379B
Coolant flange 026 121 133F
O-ring 037 121 687
Temperature switch 048 919 369
Sealing washer N 013 806.2


Install modified
flange assembly: 65 t.u.

Quality check: 10 t.u.

Labor operation: 25 19 31 0