Engine Controls - Poor Performance When Engine Is Cold
86BMW09GROUP 13 Fuel System
Bulletin Number 13 05 86 (1160) Page 1 of 4
Montvale, NJ May 1986 Technical Dept.
SUBJECT: Installation of 680 ohm resistor and temperature switch
MODELS: 325e, 528e (prior to 10/84)
Complaint: Poor engine performance under acceleration during warm-up phase.
Cause: Carbon accumulation on the intake valves and variations in the properties of fuels may cause unsatisfactory preparation of the fuel-air charge and result in hesitation under acceleration while the engine is in the warm-up temperature range.
Correction: On cars with Motronic ECU Bosch Nos. 0 261 200 021 and 0 261 200 007 only.
Prior to 10/84 production date an additional 680 ohm resistor should be installed in series with the NTC. This additional resistor is bypassed by a temperature switch when the water temperature is above 75~C.
Below 75~C, this additional resistance in series with the NTC increases the resistance sensed by Pin 13 of the Motronic ECU at any given temperature. The ECU, therefore, provides more enrichment under acceleration to provide smoother engine power.
Do not install this field fix on cars with Motronic ECU Bosch No. 0 261 200 027. Starting 10/84 these units have this fix installed internally.
The additional Resistance Kit can be obtained under Part No. 12 62 9 058 579.
Installation
Procedure: 1. Remove air filter and airflow meter
2. Cut the coolant hose (that goes from the thermostat to the throttle housing) 25 mm/1 inch in front of the plastic clip that holds it to the oil dipstick. Cut off a piece 20 mm/ 3/4 inch long from the front half of this hose.
FIGURE 1 - HEATED THROTTLE HOUSING INSTALLATION:
2a. On 1982 528e vehicles (produced prior to 5/82) refer to figure 1. The temperature switch must be installed in the coolant hose (item #3) that runs from the throttle housing to the "T" piece (item #4). The hose (3) should be cut about 2 inches away from the "T" piece (4). Before cutting this hose, hold the switch assembly (pointing downward) against the hose at the location where you intend to make the cut and ensure you have at least a 1 "clearance between the temperature switch and the starter motor electric cable.
3. Install the temperature switch onto the brass coolant pipe using the copper washer to avoid leaks.
4. Slide the hose clamps onto both ends of the coolant hose that you had cut in Step 2, and fit the two ends of the hose over the brass coolant pipe provided in the Kit. Note The temperature switch installed on the brass coolant pipe must point downward. Tighten the hose clamps.
5. Pull off white connector from the NTC.
6. Connect the additional harness in the Kit as follows:
a - White two-pin connector to NTC. b - Black two-pin male connector to engine harness that you pulled off in Step 5 from NTC. c - Two single pin black female connectors to water temperature switch that you installed in Step 4.
7. Route the additional wiring harness along the coolant hose with the temperature switch, and secure it to the hose with plastic tie straps.
8. Fill up cooling system.
9. Reinstall airflow meter and air filter.
10. Bring engine to operating temperature and turn heater knob to "full warm" position.
11. Bleed cooling system by a - opening bleeder screw until no bubbles are present in coolant; and b - loosening the 91~C temperature switch on the radiator to prevent any air entrapment.
12. Check for coolant leaks.
Warranty
Status: 1) Reimbursement for the complete repair outlined in this bulletin will be provided through normal Warranty claim processing with no limitation on age or mileage of the affected vehicle, only when this repair is performed in conjunction with and within the limits described in the BMW "86 ENGINE CAMPAIGN", and the repair is performed on or before May 31, 1987.
The "complete repair" must use the following special defect code and labor operation number:
Defect code: 00 00 99 07 00
Labor Allowance: 5 FRU Labor operation #: 00 50 536
2) If a component installed as part of the "complete repair" requires subsequent (later) replacement, the required repair will be reimburseable ONLY under the normal BMW Limited Warranty for that particular item, using an applicable defect code (NOT the "special defect code") and labor operation from the Flat Rate Manual.