I have a Citroen C4 1.4 with 1360cc 16V KFU / ET3J4 petrol engine with 120.000 km. This problem appeared 3 - 4 years ago at around 40.000 km.

When the engine is cold / hot there is a flat spot between 1000 - 2500 RPM's, and very low power. Ocassionaly when starting the car cold or hot, it would shake without wanting to rev up before shutting down. Smell from exhaust is best described like fault fuel smell. When driving and pressing the gas pedal instantly, there's a half second lag before the power actually kicks in.

There's a constant Antipollution Fault error on the dash, and scans showed that there is a P0171 (Richness Adjustment: Bottom Limit) code stored in memory, although after cleaning the code it didn't showed up again. (The ECU is Magnetti Marelli).

So far I've checked the plugs, coil pack, EGR valve and MAP sensor. I've been to a Citroen service center and all they did was clean the throttle body, but this doesn't really cured the problem, it only maked the power curve of the car a bit strange. (I've also noticed that the mechanics in the Citroen dealership drilled a small hole in the throttle flap because the flap apparently only oppened 80%?)

Recently I've also been to a friend of my who makes some readings and concluded that the front lambda sensor is faulty, but after disconnecting the sensor from the car, the simptoms were there and the car feeled exactly the same!

Do you have any experience with this engine and this kind of problem? What should be the next step I should take in finding the core of this problem?


  • Why didn't you replace the lambda sensor if it is faulty? – HandyHowie Nov 15 '15 at 14:23
  • As I've said. I've disconnected the lambda sensor completely but the problem still occured, which means this problem isn't related to the lambda sensor at all. The disconnected sensor didn't make any changes to the way the card handles. Also, this problem is intermittent. It doesn't occur everytime I start the car. 10 minutes ago I started the car cold and the idle was fine. I went to the gas station, filled it up with gas and on the next start the stuttering at idle was here and the card bogged down. – Petar Petkovski Nov 15 '15 at 14:34
  • Does your car have a MAF sensor? If so I suggest you disconnect it and report of you feel any difference. Your car seems to be running far too rich... We need to determine if it is a sensor issue or physical issue – Zaid Nov 15 '15 at 15:25
  • Yes it has a MAF sensor located on the throttle body. It was thoroughly cleaned. When the MAF sensor is disconnected the dash reports "Main Eng. Fault" and the idle goes up and down and up and down. The throttle pedal feels not responsice at all in this case. Is it MAF or MAP? Here's the link to the part: vehiclepartsdatabase.com/vehicles/allprivateroadvehicles/… – Petar Petkovski Nov 15 '15 at 15:29
  • Searching through various forums related to this problem, someone mentioned "camshaft stuck fully advance", and someone else mentioned "faulty coolant sensor". Another symptom that I forgot to mention is that I'm often loosing coolant and I need to add up some every month or so. – Petar Petkovski Nov 15 '15 at 15:51

Apparently it was diagnosed by a specialist that there is a hardware / software problem with the ECU (Magneti Marelli) that is causing all this problems, and needs to be changed. There is nothing wrong with the sensors, coil pack or mechanical parts.

  • At least you got it fixed. You should award yourself the answer. – DucatiKiller Jan 19 '16 at 15:37

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