Boxer 16v - Idle advise needed! - Alfa Romeo Forum
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Location: Gothenburg - Sweden
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33 16v

Boxer 16v - Idle advise needed!

Im actually pleased the way the engine is running, but the Swedish MOT-staff are not impressed.

The engine was oscillating between below 2000 - slightly above 3000rpm with a steady pedal when one tries to achive 2500rpm steady idle. I've had the idle valve off, cleaning it as good as I could and the sprayed some 5-56 in it before i had it attached again.

With the engine off it's possible to hear the throttle click-noise from the switch just as the throttles are about to open, which sounds all ok. BUT, when I moved the throttle switch so that it was on all the time, it was possible to keep a steady idle at, e.g. 2500rpm. This does not feel right, but it is running normally.

However, at the MOT it failed the exhaust requirements at 2500rpm, and it had the following readings (requirement in brackets).

CO 1,9 (0,3)
Lambda 0,94 (0,97 - 1,03)

So, it's running rich, but the lamda sensor is new (original bosch), so why is that? Should it not compensate? If I disconnect the air mass meter the engine is running very rough, and almost stalls. When I disconnect the temp sensor (to the motronic) the engine stalls directly.

Any thoughts or advices?

I think the next step for me is to buy a wide band lambda sensor, so i can see what's happening when I do different kind off suff. But advices are very welcome anyhow.
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Hi Maldini,

Leaks in the air intake system can cause irregular or high idle.
If outside air can enter the intake behind the airflow meter,
that "unmetered" air is altering the mixture.
Check the rubber hose for cracks between the airflow meter
and the intake manifold. Check the clamps also.
There is a vacuum distributor pipe under the intake manifold,
this is a black plastic pipe with multiple connections.
5 thin and a thick pipe connectig to it (if i recall correctly).
All connected pipes must be air-tight.
Unmetered air can also enter through the brake servo pipes,
or through the defective one way valve between the servo drum
and the intake.
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16v , advise , boxer , idle , needed

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