7 minutes ago, the_slug said:

I would assume this is something the dealership would be able to spot (I would hope so anyway)

 

If it has been mapped the car will have a TD1 flag which will tell them somthing has been changed and the checksum is wrong in the ECU

2 hours ago, flybynite said:

 

If it has been mapped the car will have a TD1 flag which will tell them somthing has been changed and the checksum is wrong in the ECU

 

Excellent. I'll make sure to mention it anyway.

 

Thank you for your help so far @flybynite

Update -

 

Skoda garage can see the misfire, they can see the car has disabled cylinder 2 to protect itself, but they can't find the cause. 

It's now gone up the chain to their "Master Technician" to look into as the tech I spoke to on the phone was baffled. He did seem like he cared though at least. 

 

They're going to keep it overnight so I guess I'll update you all tomorrow 😞 

23 minutes ago, the_slug said:

Skoda garage can see the misfire, they can see the car has disabled cylinder 2 to protect itself, but they can't find the cause. 

 

Well that is at least some progress, they have acnowledged the fault and are looking for the cause. It could be anything but being on 1 cylinder narrows it down. Sticking valve, bad injector, bad sensor (not many are cylinder specific) could all lead the car to protect itself. It would be interesting to see the AFR at the point of misfire. That cylinder is possibly going lean to the point of detonation. 

 

I would be checking the cylinder physically before doing anything fancy. Compression test, leak-down test. Injector performance.

1 hour ago, flybynite said:

I would be checking the cylinder physically before doing anything fancy. Compression test, leak-down test. Injector performance.

 

Agreed. I just called them back and asked them to make sure a compression test is carried out before we go changing/investigating anything further. 

Update -

 

Car has not been mapped, they checked the ECU and everything checks out.

Compression is fine, these are the results -

 

Cylinder 1: 13.2 bar
Cylinder 2: 11.4 bar
Cylinder 3: 13.4 bar
Cylinder 4: 11.4 bar

 

Acceptable range: 11-14 Bar

 

 

The techs have checked the plugs and coils, all are fine. They even commented that the plugs in the car are better than what they usually see. At least there's something positive! 🤣

 

So myself and the techs are in agreement that the fuel delivery must be the problem. If we've got spark, and we've got compression there's nothing else it can be. 

The master tech is going to try and monitor the AFR during idle once the car has cooled down and see if they can spot which injector might be playing up.

 

Progress is slow, but at least we're getting somewhere. 

@flybynite I don't suppose you know what conditions the car uses each set of injectors do you? IE: what set are being used when warming up at idle?

Update #2 -

 

They pulled all 4 injectors that sit above the intake manifold and injector #2 was significantly more dirty behind the rubber seal than the rest. 

The injectors have been cleaned and the injector from #2 has been moved into cylinder #1. The technician is now hoping we'll see errors logged against #1, or the problem is now fixed.

 

I guess we'll wait and see.

4 hours ago, the_slug said:

@flybynite I don't suppose you know what conditions the car uses each set of injectors do you? IE: what set are being used when warming up at idle?

 

AFAIK the car uses direct injection for warm up idle, and for high, revs full load, full boost etc. Manifold injection for everything else.

 

It makes sense that it is the manifold injector that is giving issue. Looks like it may be the culprit. 

 

I dont know how they cleaned it but injector cleaning is a fairly specialised process. Giving it a blast with carb cleaner may not improve things but at least it should move to the other cylinder.

 

Fingers crossed an answer soon 🤞

Update #3

 

Well it's been 3 days and so far, no misfires at idle.

I've been monitoring the car constantly while driving and so far only 2 misfires have been logged in about 90 miles of driving. This is normal so I'm not worried about this.

The problem was intermittent before, so it could just be plain luck so i'm going to give it another week before I start to feel relief!

 

@flybynite There's something that's bothering me about the compression readings I got from the dealership. It appears half of the cylinders are quite far apart in their compression (2 BAR) I know the compression is within spec, but could such a difference between cylinders cause a problem?

 

Looks like I'm probably fine:

5 hours ago, the_slug said:

There's something that's bothering me about the compression readings I got from the dealership. It appears half of the cylinders are quite far apart in their compression (2 BAR) I know the compression is within spec, but could such a difference between cylinders cause a problem?

 

I wouldn't be too concened, it is within spec, most will never know their compression readings, sometimes ignorance is bliss.

 

Unless it was a full leak-down test, it may be down to one of those micky mouse push on testers, basic compression test only shows so much anyway.

 

As one injector was full of crud and a second cylinder had an occasional misfire, it is not out of the bounds of possibility it is a bit coked up. I would run it on Shell V-Power (or similar) for a bit as they do have better detergents, then warm it up well and give it a bit of a thrashing. Italian tune up does sometimes work  

Update #4

 

Well, it's been two weeks and while I can confirm the CEL hasn't come back on, and I've not had a fuel cutoff to cylinder 2 occur. The intermittent misfires are still present, and they're still happening on cylinder #2.

I'm going to keep monitoring it over the next two weeks, but I have a feeling I'm going to need to take it to a friends garage to see if they can figure this out, because I'm baffled.

 

If swapping coils to different cylinders hasn't fixed it, a whole new set of plugs hasn't fixed it, and changing the port injector over to cylinder #1 hasn't fixed it (Or at least moved the problem) then I literally have no idea what the cause would be at this point. 😞

It just doesn't make any sense. If i've got good spark, good compression, and fuel then the only thing left in my head is the factory mapping of the engine is wrong, but then other people would be reporting this on here too.

 

Any more ideas guys?

@the_slug

I take it you bought this car used since you have not had it running like this for 5 years.

?

So do you know for certain that the car has not been remapped and it is running the factory engine management?

@Roottootemoot I had the dealership check the ECU and they confirmed it hasn't been remapped. And yes, I'm the second owner of the car.

27,000 miles on it.

At this point, there's nothing else other than the DI in cylinder #2 that hasn't been replaced or at least moved. But I'm EXTREMELY reluctant to go taking the Intake manifold off only to discover the DI is absolute fine and now I've gotta pay 3 hours Labor to a mechanic.

Also, if the DI was the problem I would expect misfires or hesitation when in wide-open-throttle but no, when you're gunning it the car feels great. Free revving, no bad sounds, smooth as any strait 6 I've driven.

 

Absolutely stumped. 😞

Edited 8 October, 20196 yr by the_slug

I acutally discovered you can manipulate the engine into misfiring simply by letting it idle, then blip the thottle. If you quickly bring the RPM up to 1200-1500, when the revs begin to drop it's almost like the engine struggles to stabalise at 750RPM. You can watch the misfire counter on #2 increase by about 3-5 everytime you blip the throttle when cold. 

 

Here is a video example of what happens:

When I do it it's not as extreme, but it's very similar.

Edited 8 October, 20196 yr by the_slug

11 hours ago, the_slug said:

At this point, there's nothing else other than the DI in cylinder #2 that hasn't been replaced or at least moved.

 

Still lots of things it could be, that engine has variable valve timing and variable valve lift. Variable valve timing is unlikely to affect one cylinder but valve lift could. Oil starvation to the camshaft or valve train cause wear, sticking and binding. Have they checked valve gear? A valve not opening enough may not show on a compression test but will still cause issues

 

I would like to know if they did a full cylinder leak test not just a quick 6-rev compression test.

 

Old school stuff like wiring still apply, cuts, brakes and resistance, broken plugs etc etc. Air leaks, faulting sensors. Most, but not all would log faults.

 

They say the cylinder is protecting itself, what is causing it to do that, what parameter is going out of range to cause it to (I assume) retard the ignition far enough to misfire.

 

 

8 hours ago, flybynite said:

Have they checked valve gear? A valve not opening enough may not show on a compression test but will still cause issues

 

No, I don't believe that was checked as part of their tests. As mentioned earlier, the problem only occurs at Idle, and only when the engine is cool. And even then, its intermittent.

 

8 hours ago, flybynite said:

I would like to know if they did a full cylinder leak test not just a quick 6-rev compression test.

 

No leak down test was done, just a basic one. I'm going to get my friend to carry one out next week or the week after if he's got time.

 

8 hours ago, flybynite said:

They say the cylinder is protecting itself, what is causing it to do that, what parameter is going out of range to cause it to (I assume) retard the ignition far enough to misfire.

 

This is the part that's worrying me. The VW "Master technician" was baffled as the car was logging no reason for the shut off. It was simply logging "Misfire detected" then if sufficient misfires are detected in #2 the ECU would log a "Fuel shutoff" 

 

When speaking to the guy he was honest and blunt "I've never seen a car kill the fuel but not log a reason for it"

It's at this point they started pulling injectors and found some crap on the #2 injector.  

 

I gave my friend a call (he's been a mechanic for 40 years, and has worked on my other cars so he's not an idiot) and he was also shocked that Skoda's systems couldn't find the reason for it. Even he's doubtful he's got the tools to find the cause.  😫

Edited 9 October, 20196 yr by the_slug

It's also worth mentioning that the car isn't throwing any codes for VVL or VVT. 

@the_slug 

Did you find out what it is?

I'm experiencing exact same but on the vrs diesel 2014.

I have had a look at fuel pressure the fuel pressure drops when it starts to rough idle. If you blip the throttle it goes fine blip again it will start rough idling again. 

I have been experiencing this for a year now but it is starting to get worse noticed also when it rains it does it worse more often than dry.

No fault codes spoken to a few specialists they are saying could be fuel pressure regulator haven't yet changed them will do soon and see how that goes.

7 hours ago, Dillaz_k said:

@the_slug 

Did you find out what it is?

I'm experiencing exact same but on the vrs diesel 2014.

I have had a look at fuel pressure the fuel pressure drops when it starts to rough idle. If you blip the throttle it goes fine blip again it will start rough idling again. 

I have been experiencing this for a year now but it is starting to get worse noticed also when it rains it does it worse more often than dry.

No fault codes spoken to a few specialists they are saying could be fuel pressure regulator haven't yet changed them will do soon and see how that goes.

The engines are different. The first thing I would do is make sure everything has been serviced when it should have. Such as the fuel filter etc.

If you have access to vcds or obdeleven you could scan it to ser if there are any faults raised. 

Failing that it might be a seal on an injector that has perished but without investigation it is wrong to speculate.

I would put an injector cleaner through it aswell as a matter of course. I did on mine and got a few mpgs extra.

@Ecomatt car has been serviced.

Funny you said about injector seals i changed all 4 seals and o rings on injectors last week they where leaking from seals. Still doing it. No codes come up have obd eleven. Put injector cleaner in problem still there.

5 hours ago, Dillaz_k said:

@Ecomatt car has been serviced.

Funny you said about injector seals i changed all 4 seals and o rings on injectors last week they where leaking from seals. Still doing it. No codes come up have obd eleven. Put injector cleaner in problem still there.

What state is your dpf in? I only ask as if it is getting blocked it can cause running issues. Also have you ever had your glow plugs replaced? If one of those isnt seated correctly it can lose compression.

@Ecomatt i have had dpf removed/gutted i started noticing this issue alot more as soon as i removed dpf. 

Haven't changed glowplugs before car is on 107k now. Spoke with mechanic he said glowplugs don't need changing as you only use them for when starting car when cold and thats it and unlike petrol sparkplugs this wouldn't be the issue.

 

Do you not think it could be fuel pressure regulator? As when the fuel pressure drops thats when it has a funny idle if you blip throttle its fine and runs fine when driving and sometimes when you come to a stop on idle its perfect sometimes it's not.