The measured manifold pressure and throttle angle on my 2010 Peugeot 308 CC 1.6 THP are very bad. What could be the reas

[Altunsoy]

Hello, I've been trying to fix the problems with my car for a long time. I've replaced many electronic parts, but it hasn't solved the problem. I haven't been able to fix the car's rich fuel mixture issue. I've checked everything from the electrical system to the sensors. Even after replacing two MAP sensors, the engine shows the manifold pressure at idle at 140 mbar, fluctuating between 1700/1690/2600 mbar. Also, the measured throttle angle is shown as 0. While driving, the manifold pressure remains the same. I couldn't find the canister valve, so I disconnected its connector and attached a hose to the manifold side to prevent air leakage. I'll replace the canister valve when it arrives. I removed it because the value, which is 0 when I accelerate and then release, sometimes increases to 20%-40% or even 80%. Shouldn't it normally be between 10%-15% at idle? Water droplets are coming out of the exhaust, there's a bad smell, and whitish smoke. Please help. Thank you.

[Paul-R]

How many miles (kilometres) has the car done? How long have you had it? Did it used to be all right?

[Altunsoy]

I have no prior experience with cars, so I don't know what they were like before, but does that really matter? The pressure readings are ridiculous. I bought a canister valve tonight and I'll install it and test it. I reset the learning data with the Diagbox, let the car run on its own without revving the engine until the fan came on, then drove 10 km. When I checked again, it was still showing 0 despite the throttle angle search. The manifold pressure should be between 250 and 360, but it's reading absurd values ​​like 1400, 1700, 2200, and 140. I installed two separate MAP sensors, but the situation is still the same. What could be the reason for this? Can you help me?

[PaulC5]

The MAP pressure values might be alright since it is a petrol engine with a turbo. You could check with an absolute pressure gauge though. On idle it should be below 1000 mbar since the manifold will be under vacuum but at high revs it will be under pressure from the turbo so above 1000 mbar. If you are seeing a high pressure still at idle then it could be a wiring/connection fault of the sensor. If you rev the engine and then take your foot off the pedal the throttle plate will close and the manifold pressure should drop to probably its lowest value and well below 1000 mbar. If not already done it is worth while cleaning the throttle plate to remove any carbon build up.

[Altunsoy]

Thank you for your answers. I cleaned the throttle body 500 km ago, and even cleaned the carbon deposits from the intake valves. When I connected to a car with a MED17-4-2 engine ECU via a diagbox and checked the intake pressures, the reference value and the current pressure were almost identical, measuring 360. Later, I connected to a modified 350 HP DS3 with a MED17-4 ECU via a diagbox, and the measured pressure was the same as the reference value, or close to it. My car's ECU is also MED17-4, but my reference value is, for example, 40, while the measured value is around 1700-1900. It rarely drops to numbers like 360, but then reaches those utopian figures again. There must be something going on here.

[Altunsoy]

I disconnected the MAP sensor socket while the car was not running and measured the readings. The readings in red in the image below are the ones I measured. Then I reconnected the MAP socket and measured the pins from the back while the car was running; those are the yellow readings. Isn't that strange? I disconnected the MAP socket and started the car; the manifold pressure continued to read around 1000-2000 something. Then, to measure the ECU wiring, I applied 1.29 volts to the negative and signal terminals of the socket and checked the data with the diagnostic box, but nothing changed; it continued to read high. When I removed the 1.29 volt battery and reconnected the socket while the car was running, it started reading values ​​like 180-40-50-250. Just when I thought it was fixed, the car was cold. I think it continued to read high values ​​when it warmed up. Could the ECU be faulty? I measured the wires up to the middle socket of the ECU; there is a signal, and it's not grounding with a different wire in the socket.

[Altunsoy]

The values ​​written in red are only the values ​​obtained when the ignition is on. Then I plugged in the connector and measured the connection from the back of the connector while the car was idling; those are the values ​​written in yellow.

[PaulC5]

Sorry but I do not have enough knowledge about this to be able to help any more, hopefully somebody else may be able to help. I would just have to go to a dealer and ask them to sort it.

[Altunsoy]

Something strange started happening I unplugged all the sensors, including the MAP sensor, turbo pressure sensor, upper and lower oxygen lambda sensors, and the temperature sensor in the turbo intake manifold, but the diagnostic box was still reading the manifold pressure. I don't understand what it's reading from. It's as if the sensor is still connected, continuing to display values ​​like 100, 580, 1700, 2300, etc.

[Paul-R]

Do these values vary if the engine is running?

[Altunsoy]

Yes, yes, when the car is running and the connectors are disconnected, the turbo pressure shows around 2750. I think this is normal because it's not reading correctly. The MAP sensor continues to show values ​​close to these numbers: 105-250-800-1700-2350. If the MAP sensor wasn't working or there was a problem with its wiring, shouldn't it give a stable value like the turbo pressure? The manifold pressure continues to read very strange values. As I indicated in the image above, there's no communication problem with the connectors going to the ECU. The values ​​written in red are the values ​​shown when the ignition is on and the MAP connector is disconnected. The values ​​written in yellow are the values ​​shown when the connector is plugged in and the car is running.