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Idling fine if IAC-valve is disconnected electrically... 200 1989

posted by  Frodo on  Sun Mar 2 23:53 CST 2003
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I have a 89 B230F LH2.4 which idles between 1200-1700rpm (surging).
Have not found any vacuum leaks yet.
Tired of checking diagnose output, mostly giving codes like 1-1-3, 2-2-1, 2-3-2 (too lean mixture).
I know that 016 AMM might be the problem, but I don't have a spare yet. (AMM voltage before start 1.3V, idling 2.3-2.6V depending on RPM)
O2 voltage mostly 0.5V
Hot air is disconnected (even if temperatures is mostly around 0'C).

If I disconnect the voltage to the IAC-valve, the idling goes down to a steady 1000 rpm.

Why is idling fine when IAC valve is disconnected? Is the ECU oscillating the IAC output? No change in idling when IAC is reconnected after start. Engine running fine when driving.

If I pull the power to the ECU the engine idles rough and somethimes dies, but after some trips runs fine again. I guess this is a limited "learning" period.
When swapping AMM, should ECU be reset to remove old data?

Frode P. Bergsager
Norway
--
Frodo 240GL 89 LH2.4







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