Xantia 2.0 16V, stumbles, hesitates upon acceleration

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LFY
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Xantia 2.0 16V, stumbles, hesitates upon acceleration

Post by LFY »

Hello guys!

One of my friends has a Citroen Xantia 2.0 16V Petrol (RFV) with Bosch MP5.2 control unit.

The car stumbles and hesitates badly especially under high load acceleration.

The car has a fast idle @ around 1100 RPM. (maybe vaccuum leak).

When the car is warmed up, the MAP reads 420 - 440 which is quite high and despite high manifold pressure the injection pulse width is only 2.2 - 2.4 ms!! Strange!

I hooked up Lexia and the following DTCs showed up:



Image


I unplugged MAP sensor and went for a drive. It didn't improve the situations and the only thing that happened was the engine cutting out when I let off the throttle. Should an unplugged MAP make the engine to cut out with throttle closed?

I plugged back the MAP and unplugged TPS and that didn't see, to improve the situation either.

I listened to the clicking sound of each injector and it seemed that cylinders number 2 @ 4 had sluggish clicking sounds. I removed spark plugs and noticed that cylinders 1 @ 3 had almost normal looking plugs with whitish center electrodes but number 2 @ 4 had fouled spark plugs which i think is the results of rich condition in those cylinders.

The car spits a lot when i stand near exhaust and it doesn't idle smoothly.

My friend told me that he unplugged injectors with the engine running and some of them didn't change the engine behavior.

I suspected the fuel pump but i doubt about it because a weak fuel pump will affect the whole cylinders not just two of them.

Could it be the injectors?
Should he replace the MAP first?

They are both very expensive.
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xf1ref
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Re: Xantia 2.0 16V, stumbles, hesitates upon acceleration

Post by xf1ref »

Hello, try to change injectors between them, injector 2 with 1...or injector 3 with 4 and after that check the spark plugs.
In this way you can check if you have problems with injectors.
I will suspect also lambda sensor or pressure regulator but I think the last will affect the whole cylinders.
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LFY
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Re: Xantia 2.0 16V, stumbles, hesitates upon acceleration

Post by LFY »

Can a faulty speed sensor result in fast idle while standing still?
Maybe the ECU thinks that the car is moving and increases RPM slightly to create vacuum on brake booster.
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xantia_v6
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Re: Xantia 2.0 16V, stumbles, hesitates upon acceleration

Post by xantia_v6 »

I would start with a compression check to make sure that the engine is mechanically in good condition and then put in some new spark plugs and try to eliminate all the components that could be causing one or two cylinders to be misfiring (ignition and injectors).
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LFY
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Re: Xantia 2.0 16V, stumbles, hesitates upon acceleration

Post by LFY »

You are right but the owner claims that the car doesn't consume any oil or coolant and it hadn't any noise related to valvetrain. So I didn't check the compression.
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demag
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Re: Xantia 2.0 16V, stumbles, hesitates upon acceleration

Post by demag »

Dodgy coil pack?

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LFY
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Re: Xantia 2.0 16V, stumbles, hesitates upon acceleration

Post by LFY »

Dodgy coil pack?
He has changed coil pack recently with a brand new one (Valeo).
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LFY
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Re: Xantia 2.0 16V, stumbles, hesitates upon acceleration

Post by LFY »

Can someone explain what does "mixture adjustment top position" mean?

Does it mean that the mixture is too rich?