Technical Puzzling misfire

[Daddo63]

Hi,
Wonder if anyone can give me some suggestions on a problem with my Wife's 2009 Panda 1.3 multijet. When idling there is a slight misfire which perhaps I could describe like this;- "mmmmmmmmbrrbrrmmmmmmmmmbrbrmmmmm" but when the engine is cold or warming up its not there and also if you turn the headlights or rear window demister on the misfire dissapears but if you increase the engine revs a little with the pedal the misfire increases ie "mmbrrbrrmmbrrbrrmmbrrmm", Hope that makes sense. It runs sweet as a nut and starts no bother and is doing 65+ mpg, its just that annoying murmer at idle thats got me baffled. It doesnt throw up any fault codes and I've checked all the fuel lines for leaks in case it was sucking in air. The EGR was causing issues as it was stuck open but that has been closed and disconnected and didnt put on the eml light but hoping its not that as its a pain to change and I would imagine the misfire would be there all the time if it was that but I stand to be corrected.
Thanks in advance

 

[koalar]

Strange the ECU detects the pressure from the EGR and adjust the fueling and solenoid accordingly so when it’s not altering as it should it normally throw an engine light. Like disconnect or blanked.

Think someone with more multijet experience than me needs to come along and help

 

[koalar]

Anybody ?

 

[Goudrons]

Have you checked the fuel filter housing?
They have a screw on top and need a special tool to undo and tighten, if it's loose or not seated properly they can leak (fuel out and air in).

Diesels tend to loop the excess fuel returned from the injectors back to the pump or filter when cold to aid warming up the fuel, so if it's pulling in air before that it won't be as bad or as noticeable until it's warm and dragging all it's fuel through the filter from the tank.

Though writing that, you still have an EGR problem which won't help.
If it's open when it shouldn't it will choke the air entering the engine and cause the engine to hesitate and stutter.

It might run a while without a EML, but it will come on eventually when it starts detecting the same fault a couple of times in the same drive cycle and as it's not always open and not always closed, that might take a while.

 

[bugsymike]

Have you checked the fuel filter housing?
They have a screw on top and need a special tool to undo and tighten, if it's loose or not seated properly they can leak (fuel out and air in).

Diesels tend to loop the excess fuel returned from the injectors back to the pump or filter when cold to aid warming up the fuel, so if it's pulling in air before that it won't be as bad or as noticeable until it's warm and dragging all it's fuel through the filter from the tank.

Though writing that, you still have an EGR problem which won't help.
If it's open when it shouldn't it will choke the air entering the engine and cause the engine to hesitate and stutter.

It might run a while without a EML, but it will come on eventually when it starts detecting the same fault a couple of times in the same drive cycle and as it's not always open and not always closed, that might take a while.

Re the EGR valve, on my daughters 06 1.3 Grande Punto Multijet, I fitted a EGR blanking plate, however it threw up a EML even after drilling a hole and then subsequently larger holes in the plate as supplier advised. Roughly every six weeks I had to delete it.
Obviously putting the extra electrical load on with heated rear screen etc. the ECU tells the engine to compensate the idle speed to prevent stalling, I did wonder if wear in the accelerator pedal potentiometer could cause a slight dead spot, but I would expect an error code to show.
I can't comment specifically on your model but generally if air gets in, say overnight via a leaking fuel filter, I have found it will start happily on the fuel in the pump and injectors and then as the air gets to the pump etc. it will either misfire or stall depending on severity of leak.
Other than that any chance of contaminated fuel? Even a few drops of water or some other none combustible liquid occasional running through the system?
Many years ago in a Peugeot 504 diesel pickup I was traveling over the moors and felt the vehicle was holding back slightly at times and put it down to the strong wind.Later on draining the fuel filter and tank, which luckily had a drain plug I found water to be the cause. Most modern fuel filters have a sensor to detect that.

 

[Daddo63]

Thanks for all the advice.
I will check the fuel filter housing and fit a new egr see if that sorts it. If not I will try your other suggestions. The egr is closed at the minute and the wiring disconnected, I was going to fit a blank with a hole in it but it would appear by bugsymikes experience with the blanking plate that fitting a new egr will be the best solution.. It would appear the eml hasnt lit up because there is no eml , perhaps a previous owner has removed the bulb? I will have to investigate.

 

[bugsymike]

Thanks for all the advice.
I will check the fuel filter housing and fit a new egr see if that sorts it. If not I will try your other suggestions. The egr is closed at the minute and the wiring disconnected, I was going to fit a blank with a hole in it but it would appear by bugsymikes experience with the blanking plate that fitting a new egr will be the best solution.. It would appear the eml hasnt lit up because there is no eml , perhaps a previous owner has removed the bulb? I will have to investigate.

Yours being a bit newer may have different emission parts. Re EML I wouldn't have thought it that simple to remove bulbs to pass Mot etc as part of the test used to be checking lights came on and then went out correctly .
Have you been able to check for any error codes stored?

 

[bugsymike]

Yours being a bit newer may have different emission parts. Re EML I wouldn't have thought it that simple to remove bulbs to pass Mot etc as part of the test used to be checking lights came on and then went out correctly .
Have you been able to check for any error codes stored?
Not suggesting you try this as a bit involved, but many years ago I had a 03 Doblo van that would misfire and eventually stop during a run. It was the horrible 19D non turbo, pre common rail engine. Suspecting air in the system I jury rigged a gravity tank to the injector pump and located the problem, the plastic flow and return pipes at the tank had a leaking seal at the connector.
Of course modern common rail engines like yours generally any air in the system will stop the engine dead. So if fuel related more likely water or some other non combustible liquid as I mentioned previously.
Ran out of time on previous thread.

 

[koalar]

Some ECU on eBay have the engine light turned off. So it can be done in software

There are no bulbs in the dash. As far as I remember all the lights are surface mount soldered LEDs. It been several years since I been in one I maybe 90% sure

But yes as per post above, all codes as still stored as normal and can be read via a code reader

 

[The Panda Nut]

Have you checked the fuel filter housing?
They have a screw on top and need a special tool to undo and tighten, if it's loose or not seated properly they can leak (fuel out and air in).

Diesels tend to loop the excess fuel returned from the injectors back to the pump or filter when cold to aid warming up the fuel, so if it's pulling in air before that it won't be as bad or as noticeable until it's warm and dragging all it's fuel through the filter from the tank.

Though writing that, you still have an EGR problem which won't help.
If it's open when it shouldn't it will choke the air entering the engine and cause the engine to hesitate and stutter.

It might run a while without a EML, but it will come on eventually when it starts detecting the same fault a couple of times in the same drive cycle and as it's not always open and not always closed, that might take a while.

Many years back on a Citroen I had something similar but it was much more noticable. Eventually a new fitler housing was fitted and the problem disappeared. It could also be a developing injector problem. I always used to use Bosch service centres where they seemd to be able to spot and fix these sort of problems with seeming ease. I do wish you luck.

 

[Goudrons]

I could be anything, just have to start checking what you can.
My thinking is the filter is a serviceable part, someone might have been in there recently and not done the housing up properly.

I too had a air leak in a early Citroen AX 1.4 diesel.
I could see the bubbles as the last bit of hose to the pump was clear.

It turned out a fuel filter problem. I found it by using a long hose and bypassing everything back to the tank.
The fuel filter was a screw on canister that screwed under the end of the cylinder head to help heat the fuel and no matter what it I tried or how many different brands of filter, it wouldn't screw up and seal.
It was the mount that was dodgy.

I ended up bypassing the mount and stuck in a inlne filter and it was back to normal.

I kind of liked that car, you could hammer it flat out all day and it still wouldn't dip under 65 mpg.
It had a bit of a sad death, the mount to the lower wishbone rotted away and the front nearside wheel and suspension over took me on the snake pass one winters night.