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Old 04-17-2021, 08:58 AM   #1
Lindberg_E
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Default 245 B21FT high idle (2,5k)

Hi!
Started the 245 Turbo back up after converting it back to K-jet from LH 2.4 and now it won't idle. Rises right up to about 2,5k to 3k and stays there.
It's a 1983 245 Turbo with B21FT and M46

Blocked of the idle control motor and idle stays at about 850rpm.

- Good tach signal.
- Coolant temp sensor readings are ok (hot and cold).
- 20ohm between both outer and the middle wire on idle control motor.
- Throttle switch is correct and ok, compared it with 2 other runnings cars.
Everything is measured at the control unit to confirm that the wiring is ok.
- Power and ground at control unit.

Engine wiring harness is a new one from Volvo and both firewall connectors replaced (have double checked that all wires are correct from control unit to each component.

Tried with another idle control motor and at least 5 different control units without any results.

What have I missed?
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Old 04-17-2021, 02:20 PM   #2
dl242gt
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When you checked the throttle switch did you measure it with an ohm meter? I have had those switches click like they are fine and not open and close the contacts. Without the throttle switch you can have a high idle. Another thing that is very important is to have the engine coolant temp sensor working. The idle computer uses engine temp to give you a cold higher idle. A fault like an open in that circuit will make the computer think it's -30F ambient temp.
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1982 242 turbo. 338k miles. MVP coilovers and 3" exhaust. Flowed 405 with a V15. Cossie turbine housing with upgraded compressor housing. 90+, IPD remote oil filter. Some other goodness, too. Been lots of fun over 25 years. Restored in 2k. Now ready for a 2nd restoration.

1993 245 Classic, 430k miles, enem V15. IPD bars and chassis braces. Simons sport exhaust from Scandix. sbabbs ezk chip. Been a good road warrior. Genuine Volvo rebuilt leaky M47.
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Old 04-17-2021, 03:03 PM   #3
Lindberg_E
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Quote:
Originally Posted by dl242gt View Post
When you checked the throttle switch did you measure it with an ohm meter? I have had those switches click like they are fine and not open and close the contacts. Without the throttle switch you can have a high idle. Another thing that is very important is to have the engine coolant temp sensor working. The idle computer uses engine temp to give you a cold higher idle. A fault like an open in that circuit will make the computer think it's -30F ambient temp.
Used a test lamp at the control unit to check the throttle switch (postitive to yellow wire)
I get a weak light when ignition is on and fully illuminates when throttle is pressed.
Both my 242 and another 245's throttle switches does the same but with good idle.

Coolant temp sensor is a new Bosch sensor, checked resistance with the manual and it's within spec, measured at the control unit.
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Old 04-17-2021, 03:29 PM   #4
hiperfauto
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What happens when you ground the blue/white test lead?
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Old 04-17-2021, 03:47 PM   #5
Lindberg_E
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What happens when you ground the blue/white test lead?
Nothing, behaves exactly the same
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Old 04-17-2021, 04:32 PM   #6
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Maybe the 3 wires to the IAC are swapped somehow? Or maybe there's no power to the CIS box?
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Old 04-17-2021, 04:40 PM   #7
hiperfauto
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Have you checked the wires at the idle motor to make sure they're in the correct location? Try swapping the outer 2 wires (white & green) in the connector. The center wire should be brown.

I got a repro LH2.2 engine harness made in the Netherlands and the car wouldn't run after I installed it. It turned out the 2 wires for the ignition had been swapped in the connector.
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Old 04-17-2021, 05:08 PM   #8
Lindberg_E
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Quote:
Originally Posted by bobxyz View Post
Maybe the 3 wires to the IAC are swapped somehow? Or maybe there's no power to the CIS box?
Switched the wires for the IAC at the control unit and that did it!
Idle's a bit rough but a lot better then 2,5k
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Old 04-17-2021, 05:15 PM   #9
Lindberg_E
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Quote:
Originally Posted by hiperfauto View Post
Have you checked the wires at the idle motor to make sure they're in the correct location? Try swapping the outer 2 wires (white & green) in the connector. The center wire should be brown.

I got a repro LH2.2 engine harness made in the Netherlands and the car wouldn't run after I installed it. It turned out the 2 wires for the ignition had been swapped in the connector.
That did it! They where switched at the IAC, it's a Volvo harness that doesn't look to have been used before, now i know why it probably never got installed
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Old 04-19-2021, 06:50 PM   #10
dl242gt
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Glad you got that sorted out.
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