Experience of curing a misfire

[andreweorr]

Hello All,

I wonder if anyone has any experience they could share of resolving a misfire. Car is a 2019 Leon ST 1.5TSI FR, 40,000miles, serviced yearly, completely standard, etc.

We became aware of an intermittent rough idle and reduction in power for a couple of weeks before the EPC and EML light started flashing/steady, often resetting with each start up and illuminating after several minutes driving. Generic code reader showed P0301 (misfire cylinder 1). I've replaced the plugs and moved the coil packs: 1 - 3 and 2 - 4. Problem persists.

It's now with a Seat garage who have run diagnostics to confirm fuel pressure, injectors, coil packs and plugs are all good. Injectors were 'scoped. The wiring harness from ECU to coil packs was highlighted on the 'test plan' but has tested fine. It could be carbon build up on the inlet valves..

It's being suggested that V-Power fuel with a Seat additive be added and run through the car to see if that helps reduce any possible carbon. We should hopefully get the car back tomorrow, probably not fixed but with known good fuel and an additive, for us to 'test drive' in the hope we see an improvement.

Next step would be to remove inlet manifold to inspect valves, and a clean, assuming the head doesn't need to come off..

Anyone had a similar issue? I suspect not as an online search hasn't revealed much. Your insight, however, would be very welcome!

Thanks, Andrew

 

[Decimator]

Hello All,

I wonder if anyone has any experience they could share of resolving a misfire. Car is a 2019 Leon ST 1.5TSI FR, 40,000miles, serviced yearly, completely standard, etc.

We became aware of an intermittent rough idle and reduction in power for a couple of weeks before the EPC and EML light started flashing/steady, often resetting with each start up and illuminating after several minutes driving. Generic code reader showed P0301 (misfire cylinder 1). I've replaced the plugs and moved the coil packs: 1 - 3 and 2 - 4. Problem persists.

It's now with a Seat garage who have run diagnostics to confirm fuel pressure, injectors, coil packs and plugs are all good. Injectors were 'scoped. The wiring harness from ECU to coil packs was highlighted on the 'test plan' but has tested fine. It could be carbon build up on the inlet valves..

It's being suggested that V-Power fuel with a Seat additive be added and run through the car to see if that helps reduce any possible carbon. We should hopefully get the car back tomorrow, probably not fixed but with known good fuel and an additive, for us to 'test drive' in the hope we see an improvement.

Next step would be to remove inlet manifold to inspect valves, and a clean, assuming the head doesn't need to come off..

Anyone had a similar issue? I suspect not as an online search hasn't revealed much. Your insight, however, would be very welcome!

Thanks, Andrew

Could probably try intake carbon cleaner see if it helps any bit, would be the cheapest easiest option first just have to take off the air box and spray it through the intake

 

[RUM4MO]

Could probably try intake carbon cleaner see if it helps any bit, would be the cheapest easiest option first just have to take off the air box and spray it through the intake

Do you have any evidence that cleaning out the inlet port area using sprays really works, I'm asking as I'd doubt that much improvement would result from using that method. I'd think that only hammering these areas using either walnut shells or dry ice would clean these areas up.

 

[James_R]

Walnut blasting is the only way to get the valves back to new. There are no miracle inlet cleaning sprays. That said, at 40k I sincerely doubt they are bad enough to be causing a misfire. You can check with a borescope rather than popping the manifold off.

I don't see any mention of a compression or cylinder leak-down check? Basic tasks required to ascertain the integrity of the engine internals.

My honest opinion? If the ONLY code you have is one for a misfire on cylinder 1 and it is persistent, the only other causes could be the mechanical failure of something in the cylinder (valve, piston, bore, rings) or the injector. Unless you have a static misfire (one that occurs all the time) then scoping the injector and comparing the trace to the others might not show anything up at that point in time. Even live data for the injectors won't give you a definitive diagnosis unless it's faulting at the exact moment your looking at the data.

So if the compression and leak down tests come back ok, there's only one other possibility - the injector, and for the cost of removing the manifold, you might as well replace the injector whilst you're there.

 

[nd-photo.nl]

Saw this video yesterday. Might be worth doublechecking

 

[andreweorr]

Hi All,

Thank you for your replies, plenty to think about, I appreciate that. We've still not got the car back as they don't want to release it with the persistent misfire. I've had a wee update though.

History of the car is that it was losing a small amount of coolant over the last few months. No obvious contamination in either coolant or engine so I presumed the leak was external and maybe landing on the plastic under tray - I haven't had a chance to fully inspect that as the car is my wife's daily.

The dealer have checked compression and leak down - all good. However, 'scoping the cylinders has revealed pretty clear evidence of coolant in the bores. The codes I had read were exclusively P0301, except for one occasion of a P0304. Dealer said they have seen the ECU interpret multiple cylinder misfires as being only a single cylinder.

Anyway, it seems that the charge cooler has failed in some way, and is allowing coolant to leak into the head. The car didn't typically misfire when cold but would develop one once up to temperature, suggesting expansion may be exacerbating a perished seal or crack in the cooler core, for example. The dealer have replaced quite a few charge coolers for similar reasons..

Anyway, that's what I know so far! I'll keep you updated. Thanks again

 

[James_R]

The charge cooler leaking can cause heavy contamination on the back of the valves with crystallised coolant.

 

[andreweorr]

Hey All,

I've had the report and the work has been done. Car now running sweetly

Issue was a leaking charge cooler causing heavy coolant contamination in the inlet manifold and cylinder head. See attached pics

Thanks to you all for your input. I hope this update is of help to someone in the future.

Andrew

 

[RUM4MO]

Oh, that's not good, how much coolant was this car using to cause this?

Is this becoming a regular failure for EA211 engines?

 

[James_R]

I wouldn't say regular, I've come across it a handful of times.

 

[nd-photo.nl]

Holy crap!

 

[andreweorr]

Oh, that's not good, how much coolant was this car using to cause this?

Is this becoming a regular failure for EA211 engines?

About 3 expansion tank’s worth, over a couple of months, maybe slightly longer..
I’m kicking myself because I knew I had a leak somewhere but didn’t have the time (or prioritise the time) to investigate fully.
first couple of coolant fills there was no misfire, and as I could see no contamination in either engine oil or coolant I assumed the slow leak was external.
At the first misfire I should have considered this, but there you go. Lesson learned for me!

 

[RUM4MO]

About 3 expansion tank’s worth, over a couple of months, maybe slightly longer..
I’m kicking myself because I knew I had a leak somewhere but didn’t have the time (or prioritise the time) to investigate fully.
first couple of coolant fills there was no misfire, and as I could see no contamination in either engine oil or coolant I assumed the slow leak was external.
At the first misfire I should have considered this, but there you go. Lesson learned for me!

Don't beat yourself over this, lots more of us would have not considered that that was happening - this has got me concerned though, I wonder if this is due in any way to the rather rapid, relatively speaking, drop off in protection provided by the G13, in the case of these EA221 family of engines, not having "mit silikat" expansion tanks to keep it from heading towards being acidic?

I know that this does happen, I'm monitoring it in my wife's 2015 VW Polo 1.2TSI and plan to replace the coolant as soon as I get the cam belt replaced, dropping in G12evo.

On the other hand, your car is a lot younger than my wife's Polo, hum, though I'm guessing that your car does not have a "mit silikat" reservoir/expansion tank.

 

[James_R]

It's a completely random occurrence. I've seen it happen on cars less than 12 months old. There appears to be no pattern or signs of influence.

 

[RUM4MO]

It's a completely random occurrence. I've seen it happen on cars less than 12 months old. There appears to be no pattern or signs of influence.

Okay, I'll calm down now.