[Solved] Citroen C5 II 2.0HDI RHR - Gentle jerking of the engine between 1200-2000rpm

Hello, Patient Citroen C5 2.0 HDI 136 horses, RHR engine. There is a problem with the car that it jerks unevenly when driving gently, more maintaining speed in the 1200-2000 rpm range, above that this effect disappears. The car is after delicate mechanical transitions, there have been several repairs here they are:
-repaired turbocharger, a new coras was put in, only the shells were left, made by a company from Stalowa Wola.
-The entire intake system was cleaned, as the turbo had leaked oil.
-The catalytic converters and FAP were cleaned as far as possible, because the oil had been carried out of the turbo through the exhaust.
-Removed a lubrication defect in the turbo (hence its damage - worn out shaft completely).

And now, we're driving, we're at 40kmh, the revs are around 1500rpm and you can feel this kind of gentle jerking, like there's no power at these moments.
What has been done:
-replacement of the flow meter, for a second working one, no change
-replacement of EGR with another functioning one, also no change
-replacement of EGR, and the same thing happened, also jerking

Only disconnecting the EGR (plug) gives a 100% improvement and no jerking, likewise disconnecting the flow meter no jerking, even with the EGR plugged in. What is the problem?

The lexia shows no errors, parameters within norms, I did logs yesterday of course, I have snapshots, I'll insert soon.
I did an overflow test, counting the injectors one by one from the timing side, it 1 poured 19ml, 2,3,4 16ml.
For now I will say, I don't like the injector corrections at idle:
1 101.3%
2 96%
3 102%
4 105%

While driving 103.9% all.
I added 100ml of 2T oil to the fuel, the corrections improved slightly, i.e. the 4th injector dropped to 102%, the 2nd fluctuated unchanged for a total of greater....
I would ask for help as I am already outgrowing the car. Personally I suspect a damaged FAP due to oil that has pushed through to the end of the exhaust. It's slightly pushed I believe. I'll post logs of what the airflow, turbo control and EGR looks like before long. Thanks.

With the EGR unplugged: flow from the airflow as well as from the turbo identical
.

With the EGR added below: slight ripple, marked jerk at 34th second. You can see such a tooth...




.

Perhaps someone can suggest something?

both rule out EGR operation.
I would go in this direction.

But what do you suggest? EGR replaced, flow meter also.... I'm leaning towards injection rather, but I don't know if it's the right lead?

I see a lot of airflow increase and it shouldn't.
I struggled with this once, check or replace the turbo position sensor.

In my case there was a problem with precisely this sensor and after replacing it ok.

It's not the sensor, checked, indications correct with those assumed by the ECU. Today another overflow test after using mixol: injection 1: 15ml/4min, injection 2,3,4:10ml/4min on a warmed up car. What the devil, gentlemen?

lukashb wrote:

It's not the sensor, checked, indications correct with those assumed by the ECU. Today another overflow test after applying mixol: injection 1: 15ml/4min, injection 2,3,4:10ml/4min on a warmed up car. What the devil gentlemen?

.


I have not yet had a case where diagnostics have shown this potentiometer to be faulty.

Very often there are pins which the tester and ECU do not register.

I had a similar problem in a 2012 Corsa 1.3 multijet, once in a while when driving steadily I could feel jerking, but only on a well warmed up engine (after driving 20-30km) The cause was the egr valve, after replacing it with a new one it returned to normal and the computer did not give any error and the parameters were also within normal limits.

Check the lambda probe ps co admittedly had a problem in petrol.

I suggest replacing the throttle. In these throttle bodies, the teeth on the flap which is closed wear out quite quickly. This can be checked by removing the flat cover on the throttle.

If this jerking occurs during a FAP burnout, then as a colleague above pointed out, there may be a problem with the hot air flap. When firing the FAP, it is opened and the cold air flap (from the intercoller) is closed. The other possibility is a leak on the control hoses (vacuum controlled flaps). With the engine off, pull the hoses off the flaps and try blowing into these hoses with your mouth. The author wrote that he suspects a faulty FAP. If the FAP was clogged, the controller would detect this by the differential pressure between intake and exhaust and maybe try to burn it out, and a problem with the flap, hose or control valve, would cause the engine to throttle. These are my thoughts.

In the third picture you have:
Airflow setpoint - 251
Measured airflow - 261
Was this measurement taken on a stuck EGR?

So yes, the throttle bypassing the intercooler is in working order, I tested its tightness and the operation of the dampers with a vacuum from a syringe, then with a dampers test in a lexia - all is fine, dampers are running, diaphragms are fine, holds vacuum. Throttle valve cleaned thoroughly. The jerking occurs constantly, most after warming up when the fuel dose drops due to temperature. When cold it is not felt. During fap firing fact, there is such a jerk, but it is completely different in feel, but yes, it is there. All hoses checked for leaks, from the pump itself through the vacuum accumulator, to each of the 3 valves and to the turbo and throttle. Tight. Intake manifold removed, cleaned of carbon deposits, a massive amount of carbon deposits by the way. Did not help.
I suspect fap due to the fact that the car has a poor history, the previous owner (German) was blind and deaf probably, and did not notice the turbo fault. The oil in the engine that was (a good 5l almost goes in there) went out the exhaust, through the catalytic converters and just the FAP. While I burned out the first catalytic converter and poured almost 500ml of oil out of it after warming up, I did not clean the rest myself only after the car had already warmed up after the turbo repair, the exhausts themselves chased out the rest of the oil, here almost a litre was still there. After that, it stopped kicking up from the exhaust and, all in all, we thought there was no more oil. But what was sintered on the walls on the fap ceramic remained in the The oil got charred and that was it. We also have the problem of figuring out if the injection is damaged one or not, there is too much overflow on it, and in the lexia there is too much correction on it (100% vs 105-107% on the damaged one). On top of that, the car has a terrible blowout from the crankcase, oil mist flies out where it can when the oil cap is removed, e.g. does it constantly fly with a dipstick and the whole soundproofing has stains. I personally say that due to the reduced compression and so quite low for a diezle (RHR 20bar!) one injection has to overfuel. Hence the kicking strong which kills the fap and this burns out after 200km, sometimes 300km. On idle the ecu corrects the doses so it runs evenly, while driving the doses are constant due to constant revs and I have jerking, because one cylinder is weaker. Plus the blowing from the gearbox in my opinion speaks for the ring. The man previous to this poured longlajf if there is one at all in this make, but forgot to change for a long time I think. I flushed the engine with paraffin and oil and then paraffin alone. A lot of sludge drained out. What do you gentlemen think of this?

And how about elois firing fluid. Have you already done a refill. If so, I would suggest cleaning the FAP filter mechanically. Only the soot is burnt out while the elois fluid oxide remains in the filter and clogs the filter. There is a video on YT on how to clean the fap filter in a C5. In my case, they cleaned the filter with compressed air. But after cleaning you have to upload a "new filter". If the filter is clogged it will blow your filter gasket in a while.

A top up was not physically necessary, the car has a full tank of eloys. I did a reset of just the filter and a fluid reset instead, surprisingly it started dosing fluid from now on as it was so constant the value was at 141g. It is currently approaching 150g or more, I need to hook up and take a read. So far I'm circling around 1 cylinder and lower compression, and higher dosage on this injection (4 injection 1 cylinder, oh these French, reverse ) if it's confirmed that this is the problem here, that's bad. Greetings

And what is the mileage of the car

At the time of purchase 196000km, vintage end of 2005.

This additive has a maximum service life of 180,000 km, so it was added. When topping up, the fap filter should also be replaced, but this is not done because it is expensive. If it is possible to wash it physically. And enter the new filter in the programme. The filter has two sensors, one in front of the filter and one behind. Perhaps the computer is not able to control the engine well because the exhaust gases are not freely exhausted.

For this mileage (the best for a Polish buyer, by the way), the engine should run like a bell, and yours is probably behind the best times.

I once doped FAP in such an engine and ended up with melted pistons through faulty injectors.

Beautiful, so the injectors have to be ripped out and put on the test bench. Especially as one is overflowing and has corrections that are significant. I will be trying to pull them out next week. I will report on the results.

lukashb wrote:

Beautiful, so you have to rip out the injectors and put them on the test bench. Especially as one is overflowing and has corrections that are significant. I will be trying to pull them out next week. I'll let you know the results.

You do realise that this probably won't do anything ?

So what do you think it could be? because I'm already getting lost....

lukashb wrote:

So what do you think it could be? because I'm already getting lost...

Haven't checked that potentiometer I was talking about yet.

I will have a look at it within two days. I'll let you know what happens next.

If you have a drop in compression on any of the cylinders then you have the answer to your fault and, in fact, a diagnosis.

I am curious if you have already dealt with the fault.

I'll be honest, I haven't written it off for now because we're testing. But all indications are that yes.... It turned out the FAP was so badly killed it was a shock. The holes were riddled with soot. Blowing with a compressor + Karcher to flush out the cerium oxide, and programming the "new" filter with Lexia and the car lives like new. It doesn't jerk, the combustion has dropped to normal levels, and interestingly the corrections have also evened out. But this is only the 4th day of testing. We have had an extended break in repairing this car. I have indicated to a colleague to collect for a new differential pressure sensor, as in my opinion the one he has is faulty. It doesn't give an error, but with the fap killed like that, it doesn't show a pressure difference? Only barely barely after overgassing 11-20mbar and so still 0. Because of this, the Eloys dosage dropped (I remind you, full tank under the car, pump working, tested with Lexia) and instead of clearing the filter had, it was clogging up. Because the flush didn't reveal the salmon colour of this water what was flying, just plain, maybe a little. This makes me think that this sensor needs to be addressed, as I will be dismantling the filter again. What do colleagues think about this?
Greetings!

The sensor can be simply checked with a pressure pump and manometer by comparing the reading on the tester.
This additive you are writing about is CERINE, which is not the same as cerium oxide (we can polish glass with this).

After 4 years the car was repaired. Of course, it continued to jerk like in 2017, until today, where I discovered a broken vacuum tee for the swirl flap control. After the replacement, the flaps started to work, the engine throwing when extinguishing (flapper extinguishing) stopped and these jerks stopped. On top of this, all the rubber vacuums were replaced.