Engine jerking when accelerating very softly at 1500 rpm

[Harry5555]

Good morning,

since some months I have a minor problem with my Citroen C5 X7 HDI 240 built 2012.
Sometimes when I am cruising easily at around 1450 rpm, 5th or 6th gear, and need to accelerate ever so slightly to maintain the speed the engine makes a slight "jerk" for 2 or three times.
It does not happen regularly. To me it seems to occur more often when the engine is "cold" (has run some 5 Km) than when it has been driven for 20-30 Km.
It does not happen at higher speeds / rpm`s. I have been able to reproduce it when driving with the "auto speed" assistant.
In the German C5 forum there were some hints but this has been down for months now, so sad.
I tried filling in better diesel (Supra) and diesel additives. No change.
Whenever it happens, you can also see a jerk on the tachometer.
So I can rule out:

- defect on accelerator petal (effect could be reproduced using cruise assistant)
- “bad” diesel fuel
- dirty injection

The car is fresh from inspection and the drive belt was changed due to age. Diesel filter, air filter have been done. No errors to be seen with the Lexia.
Most important observation due to my opinion is, that the effect always happens at the same engine revolution of 1450 rpm.

Thanks ahead for ideas
Hartmut

[GiveMeABreak]

Hi and welcome Hartmut.

This is not unheard of and is likely an issue with the injection system that is causing the 'hesitation'. Any fault with the system and the speed control functions are disabled (speed limiter / cruise control). In your case, I know that they are not presently disabled, but it may get worse and when it does, you'll find the cruise will disengage.

The best thing is to get it hooked up to Diagbox and check for any fault codes. If none are showing after a scan, check the fault log history. There could be a temporary fault that self-clears and that may be why there is no permanent fault remaining. The fault log history should show if there have been any recurring temporary faults, along with the frequency they have been occurring. Then paste any faults you have up here with your VIN number.

[Peter.N.]

Both of mine don't like running at 1500 rpm or slower and tend to vibrate. My old XMs would pull down to almost tickover, I suspect the Hdi's have a lighter flywheel.

Peter

[moizeau]

I had this at 1500 rpm in 1st, 2nd and 3rd with very light throttle on my 1.6 16v HDI. It would rhythmically wander by about 100rpm. I've also had this at 2900 rpm in top going up hills. The latter could be driven through by flooring the throttle. At 3100 rpm it disappeared. Both times it was the MAF (2 different ones that gave the same problem but at different revs).

[hattershaun]

Your symptoms could be a failing EGR valve. I've experienced this with the 2.7HDi engine, which is similar to your 3.0HDi.
There are two EGR valves. Diagnostic tests may show airflow faults.

[Harry5555]

Your symptoms could be a failing EGR valve. I've experienced this with the 2.7HDi engine, which is similar to your 3.0HDi.
There are two EGR valves. Diagnostic tests may show airflow faults.

Hello hattershaun,

thanks for your reply. I got some information on the EGR which I placed in the below picture. It tells me nothing much, though.
Should I make the test with a running engine ? Which speed ?
Have a nice evening
Hartmut

[Cit fan 151]

I have experienced this problem on our 2012 3.0 HDI for about the past 4 years (for 80k now). I have had the dealer and other mechanics look extensively at it, but unfortunately no definitive answer. EGR seems to get mentioned on some forums, but does not appear to be a guaranteed solution in all cases.

My first experience with what appears to be an insurmountable car problem!

[Harry5555]

Hi everyone,
a short update on this with a new question. I recognized that during the cold season (< 10 °C) the jerking of the engine has not happened once. Now why could this be ? The engine itself gets warm same in winter as in summer. Something to to with outside temperature ? Sensor (in the mirror) shows temperatures outside what they are in reality. Any ideas ?

[Cit fan 151]

Ours does it in winter (<10°C) or summer and happens just before reaching normal operating temperature.

Admittedly anecdotal, but it seems worse in times of high humidity. I have wondered whether a faulty sensor might be erratically indicating fluctuation between sub-normal and normal operating temperature? Just a guess.

[Harry5555]

Actually it turns out to be precisely 18 - 19 °C. Above this, engine jerks. Below, nothing ever happens. I read in other forums this happenes in cars (Jaguar, Peugeot) where this type of FORD diesel engine is used.

Hartmut.

[Paul-R]

That looks to me to be the camera shaking on its mounting inside the car. Can you tighten anything up? What type of camera is it?