Power Loss + High Fuel Consumption

[pcovidiu]

Citroën C5 1.6 HDi (2010) Issue on Transfăgărășan – Power Loss + High Fuel Consumption

Hi everyone! Maybe someone has experienced something similar and can help me out...

I drive a 2010 Citroën C5 1.6 HDi. A few days ago, I was driving up the Transfăgărășan mountain road. Right after an overtake (early in the climb – the car in front was super slow), I noticed that the car started to lose power gradually, and the fuel consumption went up significantly, even going downhill.

Symptoms:

When I put it in neutral, the car felt like it was braking on its own.

Consumption was so high that I actually had to press the gas pedal even when going downhill, otherwise the car felt like it was about to stall.

At first I thought maybe a brake caliper was sticking, but the brakes were fine.

When I stopped at Bâlea Cascadă, I plugged in a scanner, and noticed:

The atmospheric pressure reading was around 850 mbar.

Drove a bit further and it dropped even more – by the time I was near Bâlea Lake, it was showing about 780 mbar.

What I did:

I removed the MAF sensor and gave it a few sprays of contact cleaner (that’s all I had).

From there, I started going downhill using engine braking, and by the time I reached Curtea de Argeș, the pressure reading had climbed back to ~950 mbar.

On the way to Bucharest, it returned to ~1000 mbar, and the car started running normally again.

Questions:

Has anyone experienced something similar?

Could it be a faulty or dirty MAF sensor?

Does the ECU rely on the MAF for atmospheric pressure readings? Or could it be the MAP sensor instead?

Is it worth replacing the MAF or should I investigate something else (EGR, turbo, MAP)?

Thanks in advance! Any advice is appreciated!

[mickthemaverick]

I would think that the issues may well be down to the altitude and resultant reduction of oxygen going into the engine. Since it returned to normal when you got back down I would suggest you see how it performs in normal use for the next couple of weeks.

[PaulC5]

A search suggests the hill was 2000m up and at this height the atmospheric pressure should be about 795 mbar which can vary depending on weather conditions. The car atmos pressure sensor could be in the ecu but it looks as if everything is in good order so nothing to worry about.

[Paul-R]

The car atmos pressure sensor could be in the ecu...

I believe that is the case.

[munkey]

Funny I had the same thing with my 1.6 Berlingo, for years it had terrible MPG and was pretty sluggish. I drove to the Alps crawling up steep long mountain passes and it finally threw a engine management light... it turned out to be a bad intercooler where the plastic top was supposed to be crimped onto the metal rad veins but it had become slightly un-crimped somehow. It just needed a high boost environment for a long time which we don't see on UK roads to throw the EML

The only tell tail sign was very very light misting of oil around the boost hoses but it was so little oil it just looked a tiny bit shiny. Check to see if there is any shininess/dampness or oil around the hoses and intercooler?