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I have a 1985 318i with an automatic transmission. The engine rpms go up and down while it is in park and also does it when I am decelerating to approx 15 mph and then stops again when I stop and leave it in park. What causes this? How do I fix it?

Submitted: 543 days and 13 hours ago.

Category: BMW

Value: $9

Status: CLOSED

Optional Information:
1985 BMW 318i 1.8l

Already Tried:
nothing yet.

Accepted Answer

Hello and welcome to Just answer.com, Super mechanic here. About your vehicle.
You will first want to make sure there are no vacuum leaks or any unmetered air getting into the intake. Clean the throttle body and idle air passages. If the problem still exists, you might have to follow the recommended procedure in this service bulletin, which requires some speciat equipment.
GROUP 13 Fuel System
Bulletin Number 13 03 88 (1589) Page 1 of 4
Montvale, NJ February 1988 Technical Dept.
SUBJECT: Idle Speed Fluctuation/Idle Speed Complaints

MODELS: 318i, 325e, 528e with VDO Idle Control System
Complaint: Idle speed fluctuates; idle speed deviates from specifications.

Cause: Adjustable metal idle control valve (ICV) requires adjustment.

Correction: Adjust the idle control valve using the following special equipment and procedure:

Procedure: Note: This procedure is intended as an aid in maintenance and repair, and is used only in conjunction with other labor operations.

Connect the idle control valve (ICV) current probe in series with the idle control valve and the ICV plug as shown.
Set up Fluke multimeter to read milliamps by placing the positive (red) lead in the jack marked "MA" and select the 2000 milliamp range.
3181/A

^ Connect multimeter to ICV current probe.
^ Connect BMW Service Tester and Digital Mixture Measurement unit.

^ Start engine (oil temperature should be a minimum of 140~F/C60~C).

^ Switch off air conditioning and all other electrical consumers.

^ Check current of the idle control valve with digital ammeter at the specified rpm as shown on BMW Service Tester. The current should be:

318i: 460 +/- 5mA at 850 +/- 50 rpm 318iA: 460 +/- 5mA at 750 +/- 50 rpm
If the mA and rpm readings are different from above, adjust idle control valve as follows:
1. Turn the adjustment screw on the side of the idle control valve clockwise (completely closed).

2. Slowly open the adjustment screw by turning counter-clockwise until 460 mA and the nominal rpm is reached.

NOTE: Do not turn screw too fast as you can easily overshoot the proper adjustment point.

^
Run Engine Test step 10 and assure CO (Voltage) adjustment is within specifications as per Technical Reference Information Bulletin 00 01 83 (2012).
If necessary adjust CO, then readjust milliamps and rpm to be within the above mentioned specification.
^ Disconnect BMW Service Tester and digital ammeter.
325e, 528e

^ Connect multimeter to ICV current probe.
^ Connect the BMW Service Tester and exhaust probes.

^ Start engine (oil temperature should be a minimum of 140~F/60~C).

^ Switch off air conditioning and all other electrical consumers.

^ Check current of the idle control valve with digital ammeter at the specified rpm as shown on BMW Service Tester. The current should be:

480 +/- 5mA at 700 +/- 50 rpm

^ If the mA and rpm readings are different from above, adjust idle control valve as follows:
1. Turn the adjustment screw on the side of the idle control valve clockwise (completely closed).

2. Slowly open the adjustment screw by turning counter-clockwise until 480 mA and the nominal rpm is reached.

NOTE: Do not turn screw too fast as you can easily overshoot the proper adjustment point.

^ Run Engine Test step 10 and assure CO adjustment is within specifications.

If necessary adjust CO and then readjust milliamps and rpm to be within the above mentioned specifications.
^ Disconnect BMW Service Tester and digital ammeter.
Idle Control System Troubleshooting

If, after following the adjustment procedure the idle speed continues to deviate from the specification, system troubleshooting should be undertaken.
1. Using the BMW Constant Current Generator determine whether the fault is with the idle control valve or the System.
2. With the current generator connected, the Idle Speed should return to specifications. If not, the valve is faulty and should be replaced.

3. If the engine does idle normally, the system is faulty and further troubleshooting should be performed using the idle control system diagnostics found in Group 13 of the Repair Manual.

Accepts:
Expert:	Super mechanic
Pos. Feedback:	97.6 %
Answered:	5/29/2008

ASE Certified Technician

ASE Master, 30+ years exp. former shop owner, diagnostics, driveability tech

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Complaint:	Idle speed fluctuates; idle speed deviates from specifications.
Cause:	Adjustable metal idle control valve (ICV) requires adjustment.
Correction:	Adjust the idle control valve using the following special equipment and procedure:

^	Connect multimeter to ICV current probe.
^	Connect BMW Service Tester and Digital Mixture Measurement unit.
^	Start engine (oil temperature should be a minimum of 140~F/C60~C).
^	Switch off air conditioning and all other electrical consumers.
^	Check current of the idle control valve with digital ammeter at the specified rpm as shown on BMW Service Tester. The current should be: 318i: 460 +/- 5mA at 850 +/- 50 rpm 318iA: 460 +/- 5mA at 750 +/- 50 rpm

If necessary adjust CO, then readjust milliamps and rpm to be within the above mentioned specification.
^	Disconnect BMW Service Tester and digital ammeter.

^	Connect multimeter to ICV current probe.
^	Connect the BMW Service Tester and exhaust probes.
^	Start engine (oil temperature should be a minimum of 140~F/60~C).
^	Switch off air conditioning and all other electrical consumers.
^	Check current of the idle control valve with digital ammeter at the specified rpm as shown on BMW Service Tester. The current should be: 480 +/- 5mA at 700 +/- 50 rpm
^	If the mA and rpm readings are different from above, adjust idle control valve as follows:

1.	Turn the adjustment screw on the side of the idle control valve clockwise (completely closed).
2.	Slowly open the adjustment screw by turning counter-clockwise until 480 mA and the nominal rpm is reached.

1.	Using the BMW Constant Current Generator determine whether the fault is with the idle control valve or the System.
2.	With the current generator connected, the Idle Speed should return to specifications. If not, the valve is faulty and should be replaced.
3.	If the engine does idle normally, the system is faulty and further troubleshooting should be performed using the idle control system diagnostics found in Group 13 of the Repair Manual.

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Question

I have a 1985 318i with an automatic transmission. The engine rpms go up and down while it is in park and also does it when I am decelerating to approx 15 mph and then stops again when I stop and leave it in park. What causes this? How do I fix it?

Optional Information

Optional Information: 1985 BMW 318i 1.8lAlready Tried: nothing yet.

Accepted Answer

Related BMW Questions

Optional Information:
1985 BMW 318i 1.8l

Already Tried:
nothing yet.