Jerky engine, stops without warning. 2.2 HDi auto 6 speed touring exclusive.

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charlie101
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Jerky engine, stops without warning. 2.2 HDi auto 6 speed touring exclusive.

Post by charlie101 »

Well, the engine jerks. Sometimes. While driving with steady throttle, the car starts to jerk suddenly, 1-2 seconds off, then 1-2 seconds on. This happens at any speed regardless of whether I drive with or without cruise control, regardless of whether the speed limiter is switched off or on (I never use that feature). The speed decreases when the engine is switched off, the next second the car tries to regain lost speed. The jerks continue until I change the position of the accelerator pedal, either accelerate or release the throttle, the jerks return when I, or the cruise control try to keep the speed steady. No warning light lights up on the instruments.
During the time I break to a standstill there are no jerks to be felt, and gearbox downshift normally until stop then the engine dies. It chops and stops if I try to start again shortly after. Only when I take out the key and wait a couple of minutes and start again, then the car runs flawlessly until the next time it starts hacking. It can run fine for 400 km's or 5! but it seems to be only when the engine is warm, hasn't happend with a cold engine as yet.
The engine runs well, strong and smooth without jerks if I accelerate. I have tested in anger all the way up to top speed, about 225 km to test if there is something wrong with the fuel supply or the fuel filter. Normally I keep the speed limits on the roads.
In accordance with Murfy's law, 3 times I have been to authorised Citroen work shops that has done extensive test drives with Lexia connected, the car has behaved flawlessly then. On the Lexia there has been no fault codes related to the engine problem and no codes in the history file.
My amature guess is that it either is the control module for the injectors or throttle body that is acting up. Logically the throttle body is the first to check since it decide how long time the injectors should be open.
Throttle body action should be possible to check with an oscilloscope, and that goes for the injectors as well but as I am a beginner in this area, I don't know where to best attach the probes. Lexia seems to have limitations in this area, especially when it comes to save and replay but as I am a beginner, I might not use it to its full potential.
Last edited by myglaren on 21 Aug 2021, 09:37, edited 1 time in total.
Reason: Thread title changed to English
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GiveMeABreak
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Re: Jerky engine, stops without warning. 2.2 HDi auto 6 speed touring exclusive.

Post by GiveMeABreak »

Your problem is likely to be intermittent and that can be why the cruise and speed limiter functions are temporarily disabled when the fault occurs. There may not be a permanent fault code recorded in these circumstances.

One thing I suggest you do is give the fuel system a clean. Use some Redex or STP fuel system cleaner in your next tank fill. Let that work it’s way through and use the other dose for the next tank.

Sometimes if the car has been standing for a while or the rarely gets filled you may get some diesel bacteria growing in the tank. Premium fuels can also help as they have a lot more additives and cleaners in than standard fuel. So try filling up every third or fourth tank full with a premium diesel as this will also help clean the fuel system components.

I'd make sure the fuel filter has been changed too.

I had similar issues with the C3 HDi, intermittent jerking - mostly accelerating hard or going uphill was the trigger. I stuck some fuel cleaner in and went for a drive and the next time it started and the engine started to loose power I pulled over and revved it right to the limit. It spluttered a few times, but eventually stopped and cleared what was in there. It never happened again. So maybe some diesel bug sludge or other contaminant had caused it - as again no codes showing. I used the rest of the cleaner on the next few tank fill ups and that cleared the problem.

I put it down to not using the car much over the pandemic that caused some crap to get into the fuel system.
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Re: Jerky engine, stops without warning. 2.2 HDi auto 6 speed touring exclusive.

Post by GiveMeABreak »

@ charlie101: I have deleted your other post as it was a near duplicate of the above.
charlie101
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Re: Jerky engine, stops without warning. 2.2 HDi auto 6 speed touring exclusive.

Post by charlie101 »

Thank you Marc! As I am new to the forum I made some errors. I commute to work some 50 km,s one way on mainly 110km/h roads. And since the purchase of the car have been driving it almost empty, filling up on 8 occasions until presence some 68-72 liters of diesel from different suppliers. I have also used diesel additive, additive called Nectar, in a couple of fillups. This made no difference to occasions or frequency. I have taken 25 pictures of the odometer when the engine acts up. The cruise control has nothing to do with the problem.
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Re: Jerky engine, stops without warning. 2.2 HDi auto 6 speed touring exclusive.

Post by GiveMeABreak »

Ok, so just be very careful what you are putting in the fuel system - use specific fuel system cleaners for diesels that are safe for use with direct injection diesels with particle filters. I'd still get the fuel filter changed too at the next opportunity.

I'm not sure if I understand you correctly when you say you have been driving it almost empty?

If you mean you have been letting the tank get near empty before filling it up, I would not recommend that at all, as if you do have some sludge or crap in the bottom of the tank, it is likely to get sucked up by the fuel pump and this may be causing some temporary blockages - especially going up hills when any crap in the tank may be more concentrated. I never let my tank go under a quarter / but mostly a third before I fill her up.
charlie101
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Re: Jerky engine, stops without warning. 2.2 HDi auto 6 speed touring exclusive.

Post by charlie101 »

If there is a temporary blockage in the fuel supply it should show up as fluctuating fuel pressure, rarely an on-off issue, and I suspect that should be detected by Lexia. If there should be any crud in the tank, I want to get rid of that once and for all, at any cost, and never anticipate fuel issues under a 1/4 of a tank. As I said, I have been running the tank almost dry and the issues was not more or less frequent then before. It happens at any speed, and with any fuel level in the tank.
I need to pinpoint the exact problem with diagnostic tools, no guessing. That is why I need to have electrical schematics and advice on the best procedure to hook up a oscilloscope. The fuel filter will be dissected, but not before that I know that the problem states from the fuel supply. Also, at a couple of occasions with the jerking issue going on I have been running the car up to top speed with continued acceleration, so the fuel delivery all the way to the injectors can not be the culprit in my opinion. But I don't know until I know.
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Re: Jerky engine, stops without warning. 2.2 HDi auto 6 speed touring exclusive.

Post by GiveMeABreak »

Without any fault codes it is going to be difficult to pinpoint and some fuelling issues are not enough to trigger a fault if they are intermittent. A fault picked up by the engine ECU that triggers a fault code often, but not always, leads to the engine going into backup mode with reduced engine power; until either the fault is no longer recorded or until he engine is switched off and restarted. This isn't the situation it seems in your scenario so far as you still have maximum power available - until the jerking starts. But these sorts of jerking issues are often down to fuel delivery issues. If it was a sensor playing up you would get a fault code triggered.

I only suggested running that the fuel tank dry is not really a good idea as that is where any contamination will be concentrated / reside. car jerking is often associated with dirty injectors where the fuel flow is not steady. My next suggestion would be the Mass Air Flow sensor. Give that a clean with special MAF cleaner (avoid touching the wire) as if this is failing it may be giving the wrong reading to the engine ECU. If this is the 2.2 engine (DW12C) the pump isn't in the tank on these.
Charlie Fuel Pump.PNG
A full-chip revision 'C' 'Lexia kit with Diagbox is your best friend regarding diagnostic equipment to make sure you are reading all the ECUs and constructor codes. Many basic generic aftermarket code readers are limited and cannot always read all the ECUs.
charlie101
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Re: Jerky engine, stops without warning. 2.2 HDi auto 6 speed touring exclusive.

Post by charlie101 »

Not really, The issue is only prevailing when sustaining a steady speed, with any state of acceleration no stumble is to be felt. During a session with the issue going on, with a steady acceleration the engine runs strong and smooth all the way up to top speed, that has been tested a few times. At those, and at all occasions when i try to hold a steady speed the jerking returns. Same goes when I decelerate, nothing is felt until I try to keep a steady speed. But if, and when I stop, the engine dies.
Yes, so I need to learn how to connect a oscilloscope that can record a session. And a fuel pressure sensor connected to that. That is what I want help with from the forum. I tried with 3 authorized citroen dealers to help me to pinpoint what is going on and all that I got was guesses and suggestions on what to change. Suggestions on everything up to the entire fuel system, fuel tank, pump, lines, filter and injectors and all. Basically scrap the car. That is not how a technician works. I also got an Bosch car electric shop in town that has all the equipment but does not dare to touch a Citroen.
This is what I got for the interface. The DiagBox program I am running on Win 7, on a Asus computer with a brand new SolidStateDrive. Computer bought purposely and dedicated to only run Diagbox, nothing else on it and no connection with internet.
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GiveMeABreak
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Re: Jerky engine, stops without warning. 2.2 HDi auto 6 speed touring exclusive.

Post by GiveMeABreak »

Ok, so that kit is missing a lot of hardware - I can see straight away!

See my post here for the obvious ones:

https://www.frenchcarforum.co.uk/forum/ ... 22#p624622
charlie101
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Re: Jerky engine, stops without warning. 2.2 HDi auto 6 speed touring exclusive.

Post by charlie101 »

Thank you Marc! Lovely. Would you please sell me a interface like that? I don't trust myself buying from Internet as I don't know what to look for and I can't trust just pictures from some unknown Chinese. I bought that from a friend and it worked some 5-6 times before it died on me. I've until now been only checking wires and obvious faults on it. Frustrating when having such odd trouble with the car and rapidly trying to learn basic Diagbox features at the same time. I've changed nothing on the car with the program, careful to the extreme not erasing one single code as of yet, just watching and figuring out the diagnostic features.
Hell Razor5543
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Re: Jerky engine, stops without warning. 2.2 HDi auto 6 speed touring exclusive.

Post by Hell Razor5543 »

There is a company who supply a good Lexia, with the full component set and a good reputation;

https://www.easydiagnostics.co.uk/produ ... t-vehicles
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Re: Jerky engine, stops without warning. 2.2 HDi auto 6 speed touring exclusive.

Post by GiveMeABreak »

charlie101 wrote:
23 Aug 2021, 22:33
Thank you Marc! Lovely. Would you please sell me a interface like that? I don't trust myself buying from Internet as I don't know what to look for and I can't trust just pictures from some unknown Chinese. I bought that from a friend and it worked some 5-6 times before it died on me. I've until now been only checking wires and obvious faults on it. Frustrating when having such odd trouble with the car and rapidly trying to learn basic Diagbox features at the same time. I've changed nothing on the car with the program, careful to the extreme not erasing one single code as of yet, just watching and figuring out the diagnostic features.
Hi Charlie, although we are not affiliated with Easydiagnostics, many members here have bought from them over the years, including myself. They are more expensive, but you know you are getting the full ticket and they provide support too. There is also a discount for members available, details below:

Easydiagnostics Equipment Discount for FCF Members