What kind of triggers or inputs values from the sensors are required that will shutdown the engine completely? I guess that there are several senario's?

 

is there  a system on the Fabia that will measure a misfire? If so how is this achieved?

 

Regards

Crank position sensor failure will completely shut down the engine and make it unstartable thereafter.

 

Misfire is sensed through a pair of knock sensors on the back of the block, these listen to the cylinders firing and use the aforementioned CPS to work out which one is misfiring, misfires are invariably caused by the coil packs or the wiring loom on your engine.

Thanks Spulchrave,

 

Was unable to find this information. 

 

Would be nice t have a high level design decision diagram to understand the behaviour of the ECU? Is there information that would allow me to understand these aspects? Have not seens them anywhere. Should be in the Service Manual I guess in order to also diagnose the engine and ECU

 

I do get an EPC warning light: the engine started to stall every week about 4 months ago and in the last couple of weeks it stalls a few times per week ....

 

Timing belt is at 80.000Km which could be the culprit?

 

crank postion failure would be in the ECU error log I guess, right? Does this sensor signals TDC or the actual angle of the crankshaft?

 

Thanks!

 

ps : found this nice picture diagram with all the main components, have not (yet) found the cranck postion sensor by the way.....

Edited 10 June, 201412 yr by fabiacat

Thanks Spulchrave,

 

Was unable to find this information. 

 

Would be nice t have a high level design decision diagram to understand the behaviour of the ECU? Is there information that would allow me to understand these aspects? Have not seens them anywhere. Should be in the Service Manual I guess in order to also diagnose the engine and ECU

 

I do get an EPC warning light: the engine started to stall every week about 4 months ago and in the last couple of weeks it stalls a few times per week ....

 

Timing belt is at 80.000Km which could be the culprit?

 

crank postion failure would be in the ECU error log I guess, right? Does this sensor signals TDC or the actual angle of the crankshaft?

 

Thanks!

 

ps : found this nice picture diagram with all the main components, have not (yet) found the cranck postion sensor by the way.....

 

Timing belt will not be at fault, 100k km is the precautionary change interval.

 

CPS reports crank angle accurately so the ECU can work out where all the pistons are and on what stroke, and yes, it would be flagged as intermittent if it were failing.

 

This sounds far more likely to be EGR related or possibly a failing coilpack. These engines are very temperature sensitive, does it warm up quickly and does the needle sit bang on halfway once it has done so?

have to check that in terms of temp. 

 

What is "quickly" in terms of warming up?  

 

Would it normally fluctuate move swing a bit the temp gauge on the dash? I guess normally hardly noticable changes?

 

Can you describe the theory or analysis that concludes that it could be the EGR valve? It would like to understand this.  

 

I have see ie youtube video's with EGR valves clogged up very badly because they have never been properly cleaned. Cleaning up the EGR is not rocket science...

 

Thanks!

 

ps; I guess the explaination is here http://www.wisegeek.com/how-can-i-tell-if-my-egr-valve-needs-to-be-cleaned-or-replaced.htm

which means that it would start with a rough idling and taking "long" time to warm up because of the exhaust gauses affecting or compromising the air or oxygen inlet. And when the EGR is fixed in a badly position it would really screw the whole combustion proces fooling the ECU that would through in the towl? Just an intial guess...

Edited 10 June, 201412 yr by fabiacat

Driving the car into a brick wall will definitely show symptoms of trouble re-starting the engine.

have to check that in terms of temp. 

 

What is "quickly" in terms of warming up?  

 

Would it normally fluctuate move swing a bit the temp gauge on the dash? I guess normally hardly noticable changes?

 

Can you describe the theory or analysis that concludes that it could be the EGR valve? It would like to understand this.  

 

I have see ie youtube video's with EGR valves clogged up very badly because they have never been properly cleaned. Cleaning up the EGR is not rocket science...

 

Thanks!

 

ps; I guess the explaination is here http://www.wisegeek.com/how-can-i-tell-if-my-egr-valve-needs-to-be-cleaned-or-replaced.htm

which means that it would start with a rough idling and taking "long" time to warm up because of the exhaust gauses affecting or compromising the air or oxygen inlet. And when the EGR is fixed in a badly position it would really screw the whole combustion proces fooling the ECU that would through in the towl? Just an intial guess...

 

Quickly is 5 minutes at this time of year.

 

Once the needle reaches halfway after 5 minutes it should not move again at all.

 

The engine depends heavily on the EGR valve to reduce pumping losses when the throttle is shut or nearly shut and it increases fuel economy dramatically. A stuck EGR valve can make the engine stall, you may need to replace it after 80k.

or take it completely out as opt here:

 

http://www.briskoda.net/forums/topic/295496-guide-how-to-remove-egr-valve-and-how-to-fit-the-group-buy-egr-delete-pipe/

 

??

 

btw: you would imagine that there would be a feedback to indicating a "hanging" EGR value back to the ECU since the consequences can be dramatic (loss of engine power, power stearing ànd power bleaking....)  not very "pleasant" when coming down a mountain with a caravan or something

That link is not for the petrol-engine Fabias, have a look, it's all very different.

 

Unlike on the diesels, your EGR valve does  may give position feedback to the ECU, I believe (are there 5 wires going to it?), if so the ECU should log error codes if there is a mismatch between how open it is 'asked' to be and how open it is actually. It might need to happen a number of times before it triggers a fault light.

 

I had this happen on our 1.2-engine which has a similar all-electric EGR, and it gave a code which was translated as 'control difference', code 17811, but the same codes may not apply to your engine.

 

For the 1.2 engines there is a nice full description of how things work in Self Study Programme (SSP) 260, including this description of crank and cam sensor failure consequences:

 

 

"Substitute functions

Engine speed sender G28, camshaft position

sender G163

If the engine speed sender G28 fails when the

engine is running, the engine stops. It can,

however, be started again.

If the camshaft position sender G163 fails

when the engine is running, the engine

continues running and can also be re-started.

If both senders fail, the engine cuts out and

can no longer be started."

 

I am by no means saying that your engine is the same, but I guess that's the sort of thing you're looking for?

 

An index of such SSPs is available via here. I dare say somewhere amongst that lot there's a similar description for the BBZ engine.

As Wino says you cannot delete the EGR valve on your engine, however unlike the 1.2 your EGR valve is a three-wire connection and the ECU calculates the voltage supplied to the valve using the MAP sensor to tell the difference between fully open and fully closed, this is why you need to run an adaptation program when you change the valve so that the ECU can be re-calibrated and interpolate what PWM voltage to send the valve under various engine conditions. Sometimes running that adaptation can correct EGR problems on cars where the valve may have drifted out of original spec.

Yes @Wino : that is exactly what I am looking for: it describes exactly the behaviour or the programming logic of the ECU.

 

Oke : I didn't see that taking it out is only for a diesel engine.

 

I guess that a good clean up of the EGR sounds like a very cheap very first option to see of the problem will be less severe or in other words that we are at the right track/direction which is a whole lot better than the big unknown right now........ 

 

Oke: they do have a feedback to the ECU to monitor the EGR valvue position: overall it sounds like a very good design overall and it get's applied in many VW, Skoda, Seat and Audi cars. It reminds me of the Beosound Century overall design: way ahead at that time (1999?)  and used for many many many years in many many types and it was easy to make small improvements or add small features, I think the same is true for this design. 

 

 

Question 1:  can I clean the EGR with ie W40 or do I need something special to clean the durt? I can use also an ultrasound cleaning bath: would that be a good option?

 

Question 2: will the EGR be replaced at 200.000Km including the timing belt?

 

Appriciate the very useful answers!

 

Thanks

1. The valve itself is not likely to be very dirty. It runs so hot because of its position, that any soot deposition that might occur is soon burnt away again.  The pipe that takes the recirculated gases to the inlet is where problems may occur, particularly at the colder, throttle-body/inlet manifold end where contaminants may condense. Cleaning this pipe out is probably worth more to you functionally than trying to clean out the insides of the EGR valve itself.  Oven cleaner is usually good on sooty deposits, but be sure to rinse it all away thoroughly after cleaning as it is pretty corrosive stuff.  Could perhaps thread some rope through the pipe instead and 'floss' it.  Either way, full removal of the pipe from the car required.

 

Edit: do have a good look at the valve from underneath if it's possible. Ours started to stick open because the physical casting of the main body of the EGR had 'morphed' in shape due to 'above-design' temperatures, altering the geometry of the valve seat/guide. It was apparent by the fact that a core plug in the bottom of the valve was no longer round. I'll find a picture of this given time.  Not sure if the BBZ and preceeding 4-pots had such issues.

 

2. There is no replacement schedule for EGR valves as far as I know.  Ours failed at about 100 000 miles/160 000km but as Sepulchrave has kindly mentioned, the valve is not quite the same on my engine, and the engine is radically different too!

 

Under what conditions is your engine stalling?  Near idle, pulling up at junctions and pulling away, or at higher revs too?

 

Edit: picture of bottom of AZQ engine EGR from below, core plug oval!

I get your drift Wimo, the hot gasses from the exhaust which will contain a cetain amount of moisture (read water)  will create a favor inside the much cooler air inlet pipe into which party those hot gases will flow: the condensation could also affect the combustion properties in a negative way since most of this process is very tightly scheduled using this real time ECU that will determine the amount of fuel injected and the exact ignition time. 

 

If I do understand you guys correctly is that these exhaust fumes will have directly a high temp and high moisture contents  while the temp of the engine itself might still be the outside temp just after starting the engine. I guess that this has noting to do with the overall engine temp but with the cobustion temp which can't go to heigh becaise they are for a very short window dangerorously high for the engine metal parts that are exposed to the very high combustion engine temps. That is I think the whole reason why they tampere that process by redirecting less pure oxygen into the air inlet. 

 

Am I on the right track in the above description??

 

beside the condensation the high temps of the exhaust will deform one side of the valve making it not perfectly round anymore which causes it to lock itself eventually. It is hard to see that the ring in the above picture is oval, but that could be well caused by the camera. 

 

Very interesting discussion. 

 

Thanks!

What I was trying to say is that if any part of your EGR system is blocked by sooty deposits, it is most likely to be the end of the pipe furthest from the valve itself. I'm not sure what any of your second paragraph means, all I can say is that for my engine/EGR valve, Pierburg - its manufacturer - put out a service bulletin describing how some of these valves had suffered thermal damage (including that core-plug completely falling out). 

If you do a search for the word 'wideband' you'll find a thread describing my experiences, including a link that service bulletin, I think.

 

The ovality of that core plug is not a photographic artefact, I measured the north-south dimension at over a millimetre more than the east-west, I think.

and Wino I understand that a 3 cylinder engine is a diff cattle of fish compared to a 4 cil 1.4L engine. 

 

Where would I find the description of the engine used in the 1.4L 4L 74Kw Fabia engine? I mean there is a lot, a TON of information to be found here which is vèry interesting

 

Thanks!

Quickly is 5 minutes at this time of year.

 

Once the needle reaches halfway after 5 minutes it should not move again at all.

 

The engine depends heavily on the EGR valve to reduce pumping losses when the throttle is shut or nearly shut and it increases fuel economy dramatically. A stuck EGR valve can make the engine stall, you may need to replace it after 80k.

 

The thing is that the engine also stalls at random points/times ie also when cruising, so not only when ie just idling. 

Crank position sensor failure will completely shut down the engine and make it unstartable thereafter.

 

Misfire is sensed through a pair of knock sensors on the back of the block, these listen to the cylinders firing and use the aforementioned CPS to work out which one is misfiring, misfires are invariably caused by the coil packs or the wiring loom on your engine.

 

By the way± when this stalling occurs it is possible to restart the engine directly after.  This is I think key information. So it can´t be the CPS

<snip>

 

"Substitute functions

Engine speed sender G28, camshaft position

sender G163

If the engine speed sender G28 fails when the

engine is running, the engine stops. It can,

however, be started again.

If the camshaft position sender G163 fails

when the engine is running, the engine

continues running and can also be re-started.

If both senders fail, the engine cuts out and

can no longer be started."

 

 

 

it does restart again

I've just sent a message to a man I know who may have the equivalent info for the BBZ engine with 4LV management. 

I checked the engine and here are some observations:

 

* right from the start it runs a bit irregular when looking at the bare engine : it kind of rocks just a little bit and that doesn't go away when the engine is at normal operational temp

* I listened with the back of a screwdriver as close as possible to the injectors and they all sound the same

* I listened at the front of each cylinder bay to look for any difference in terms of valve moments: also fine

* no EPC light

* the exhaust throws just spatters of water

* I could not find the EGR valve on this BBZ engine type

 

that rocking of the engine might might give a hint

 

Any recommendation what to do next? May take out the sparkplugs which may give a good overall impression per cylinder?

 

Cheers

I haven't heard back from the guy who might have access to technical info about your engine, but I can tell you where to look for the EGR valve. It might not be fitted though.  My engine AZQ was superceded by the BME code, and I'm fairly sure I read that some (later?) versions of that engine didn't have EGR function. The same may have happened with the 4-cyl 16v engines over time. There may be regional/international variations in what is used also.  Where are you and what year is the car? 2006 car as title.

 

If you have one look at No. 13 in this description here.

Interestingly, it mentions in the text a potentiometer that may be associated with it, so if you do find the valve in that position, count the pins on the electrical connector to see if yours has that.

 

Edit: some testing info here and on subsequent pages.

 

Edit2: I'm not at all sure that the EGR valve is involved in your problem, because of your observation that stalling sometimes occurs during cruise, not just near idle.  I'm not sure that an EGR valve problem could cause that.

Found I think  the manual of this BBZ block:  http://workshop-manuals.com/skoda/fabia-mk1/drive_unit/1.4/55;_1.4/59;_1.4/74_engine_fuel_injection/mixture_preparation_system_electronic_inj.gas/repairing_the_injection_system/installed_location_overview_for_engines_with_engine_identification_characters_bby_bbz_bky/

 

it does have a EGR but on a totally different place

 

more interesting stuff, readout of ECU value of all the sensors and their valid values

 

http://workshop-manuals.com/skoda/fabia-mk1/drive_unit/1.4/55;_1.4/59;_1.4/74_engine_fuel_injection/self_diagnosis_v.a.g_inspection_service/self-diagnosis_v/measured_value_blocks_display_groups_000...028/

 

lambda information

 

http://workshop-manuals.com/skoda/fabia-mk1/drive_unit/1.4/55;_1.4/59;_1.4/74_engine_fuel_injection/self_diagnosis_v.a.g_inspection_service/self-diagnosis_v/measured_value_blocks_display_groups_030...062_099/

 

ECU diagnose information:

 

http://workshop-manuals.com/skoda/fabia-mk1/drive_unit/1.4/55;_1.4/59;_1.4/74_engine_fuel_injection/self_diagnosis_v.a.g_inspection_service/self-diagnosis_v/measured_value_blocks_display_groups_070...126/

Edited 13 June, 201412 yr by fabiacat

Sounds like the engine is definitely misfiring, with no fault codes I suspect one of the coilpacks or the coilpack wiring loom.

Sepulchrave:  can I may be "hear" misfiring using a screwdriver as a hearing-aid?

 

How do I determine misfiring when the engine is just idling without using any diagnostics from the ECU? 

 

I can't read the ECU jet (have to fix laptop first....)  but I guess that the knock sensors will detect the misfiring?

 

The temp of the engine once warm is very stable.

 

BTW: this engine runs also on natural-gas and does have the same problems so I can exclude full pump and injectors. And I still don't really understand how a gas system will fit in into such a very complicated engine management system considering the function of the injectors. But that is a whole different cattle of fish

 

idling speed:

 

http://workshop-manuals.com/skoda/fabia-mk1/drive_unit/1.4/55;_1.4/59;_1.4/74_engine_fuel_injection/mixture_preparation_system_electronic_inj.gas/testing_components_and_functions/idle_testing/

Edited 13 June, 201412 yr by fabiacat

You don't have to hear it, the kicking and rocking is a misfire, you can see it.

 

It's definitely the ignition, you have a faulty coilpack or wiring loom.