1.4L tsi Misfire

[DapperH45]

1.4L tsi (czca) Engine Misfire!!!

Hi guys, I own a seat leon mk3.5 at 72k mileage and I have an engine misfire on all 4 cylinders. Symptoms include cold start misfire, rough idling, decreased fuel economy only during local driving and low rpm engine misfire (mainly between 1k - 2k rpm). I would not say poor acceleration but during the low rpm it does take a few seconds before the engine kicks in.

So far I have replaced all 4 spark plugs, all 4 ignition coils, replaced pcv and completed a smoke test (no obvious leak). Based on the symptoms and what I have already replaced any ideas what it could be? I was leaning more towards HPFP or maybe the timing is off?

Any help would be appreciated.

 

[SRGTD]

The symptoms you describe are often associated with carbon build up. More of an issue with direct injection engines, and the AI response to an internet search on your engine code suggests the engine in your car does have direct injection.

Just my ‘armchair diagnosis’ (a.k.a. guess) and other forum members might have different suggestions on the cause(s) of your misfire issue.

 

[nd-photo.nl]

@DapperH45 What mileage are we talking about here?

 

[SRGTD]

@DapperH45 What mileage are we talking about here?

The OP mentioned in their post that the car’s on 72k miles.

 

[mty12345]

1.4L tsi (czca) Engine Misfire!!!

Hi guys, I own a seat leon mk3.5 at 72k mileage and I have an engine misfire on all 4 cylinders. Symptoms include cold start misfire, rough idling, decreased fuel economy only during local driving and low rpm engine misfire (mainly between 1k - 2k rpm). I would not say poor acceleration but during the low rpm it does take a few seconds before the engine kicks in.

So far I have replaced all 4 spark plugs, all 4 ignition coils, replaced pcv and completed a smoke test (no obvious leak). Based on the symptoms and what I have already replaced any ideas what it could be? I was leaning more towards HPFP or maybe the timing is off?

Any help would be appreciated.

Do you have any fault codes? You should do if you're having that many misfires.

 

[DapperH45]

Do you have any fault codes? You should do if you're having that many misfires.

P0300 - P0304. Not telling much

 

[DapperH45]

The symptoms you describe are often associated with carbon build up. More of an issue with direct injection engines, and the AI response to an internet search on your engine code suggests the engine in your car does have direct injection.

Just my ‘armchair diagnosis’ (a.k.a. guess) and other forum members might have different suggestions on the cause(s) of your misfire issue.

Initially I did suspect carbon build-up on the intake but I would have thought symptoms would carry over under load ie motorway driving, which the car seems to be okay with.

The 1.4L tsi is less prone to carbon build-up compared to other direct engines and at 72k mileage I would have thought it would be something else. Of course this is just an assumption without looking through a borescope.

 

[SuperV8]

P0300 - P0304. Not telling much

There are multiple possible fault descriptions for both these fault codes:

P0300 - Random/multiple cylinder misfire detected
O2 sensor in front of CAT
Camshaft position sensor inlet
Crankshaft position sensor
Injector 1,2,3,4
Coil 1,2,3,4
Knock Sensor

P0304 - Cylinder 4 misfire detected
Camshaft position sensor inlet
Crankshaft position sensor
Injector 4
Coil 4

 

[nd-photo.nl]

Easy stuff to try is to swap around coils and see if the misfires move with it (even if they are new). You need to eliminate to progress on things

 

[DapperH45]

Easy stuff to try is to swap around coils and see if the misfires move with it (even if they are new). You need to eliminate to progress on things

Prior to installing new coils, I had the same codes P0300, P0301, P0302, P0303, P0304. Although they are new i would not suspect coils to be faulty as I have the same misfire codes. I suspect a shared component not individual coils.

 

[DapperH45]

There are multiple possible fault descriptions for both these fault codes:

P0300 - Random/multiple cylinder misfire detected
O2 sensor in front of CAT
Camshaft position sensor inlet
Crankshaft position sensor
Injector 1,2,3,4
Coil 1,2,3,4
Knock Sensor

P0304 - Cylinder 4 misfire detected
Camshaft position sensor inlet
Crankshaft position sensor
Injector 4
Coil 4

Apologies, the codes read out P0300 to P0304 including P0301, P0302, P0303.

 

[nd-photo.nl]

Prior to installing new coils, I had the same codes P0300, P0301, P0302, P0303, P0304. Although they are new i would not suspect coils to be faulty as I have the same misfire codes. I suspect a shared component not individual coils.

I understand (and agree), but you need to 100% rule out things, else you won't be able to resolve this issue I think

 

[mty12345]

P0300 - P0304. Not telling much

That actually tells quite a bit, the fact you're getting misfires on all four cylinders suggests it's unlikely to be an ignition issue, as it's affecting the engine as a whole rather than one or two individual cylinders.

If it were a fuel pressure issue, I'd expect to see fuel pressure or mixture-related fault codes, and for the symptoms to become more noticeable under higher load and RPM, possibly accompanied by a lean condition. Likewise, if the valve timing were far enough out to cause consistent misfires, I'd normally expect to see cam/crank correlation or timing-related fault codes.

Since the misfires mainly occur at idle and low RPM, and there don't appear to be any other relevant fault codes, I'd be looking more towards a vacuum leak or PCV system fault.

I'd start with a visual inspection of all the vacuum hoses and the PCV system, followed by a smoke test if nothing obvious is found. I'd also have a look at the fuel trims, as they'll often point you in the right direction.

 

[DapperH45]

That actually tells quite a bit, the fact you're getting misfires on all four cylinders suggests it's unlikely to be an ignition issue, as it's affecting the engine as a whole rather than one or two individual cylinders.

If it were a fuel pressure issue, I'd expect to see fuel pressure or mixture-related fault codes, and for the symptoms to become more noticeable under higher load and RPM, possibly accompanied by a lean condition. Likewise, if the valve timing were far enough out to cause consistent misfires, I'd normally expect to see cam/crank correlation or timing-related fault codes.

Since the misfires mainly occur at idle and low RPM, and there don't appear to be any other relevant fault codes, I'd be looking more towards a vacuum leak or PCV system fault.

I'd start with a visual inspection of all the vacuum hoses and the PCV system, followed by a smoke test if nothing obvious is found. I'd also have a look at the fuel trims, as they'll often point you in the right direction.

Thanks for the reply.

I did previously complete a smoke test and there were no obvious leaks found and just as a precaution I replaced the pcv valve. As I couldn’t find any vacuum leaks which is why i then started to think maybe it could be a fuel delivery issues.

What could anyone recommend the next steps I could take?

 

[mty12345]

Thanks for the reply.

I did previously complete a smoke test and there were no obvious leaks found and just as a precaution I replaced the pcv valve. As I couldn’t find any vacuum leaks which is why i then started to think maybe it could be a fuel delivery issues.

What could anyone recommend the next steps I could take?

I'd use obd2 to look at the long and short term fuel trims, see if that sheds any light on things. Maybe it's drawing in extra fuel through the EVAP system or something. Can probably check fuel pressure at the same time, although like i said would be strange if that was just at idle and low revs

 

[DapperH45]

I did a diagnostic and stft and ltft showed negative values. Both values were in excess of -5% so there must be some sort of over fuelling? One of the codes which popped up was P044100 which would confirm a fault with the EVAP system. So over fuelling occurring due to the fuel vapour not being recycled and as a result the ecu removing fuel showing negative values. Monitoring the live misfire counts showed misfires occurring across all four cylinders at idle and jumped across all four cylinders. Are there any other tests i could do to further confirm if the n80 purge valve is at fault? OR could this point to potentially another problem?

 

[SuperV8]

For fault code description:
P0441 - Evaporative emission system incorrect purge flow
Component diagnosis: V1 - Canister purge solenoid

1: check resistance:
Measure the resistance between pins 1 and 2. Is it between 23 and 28 Ω?
Yes success.
No, renew canister purge solenoid

2: check supply voltage:
Turn the ignition on. Measure the voltage on pin 1. Is it between 11 and 13.5 V?
Yes success.
No, is a bit involved - can talk you through this if you don't have 11 - 13.5V on pin 1!

3: check solenoid operation:
Disconnect the canister purge solenoid. Connect pin 2 to the negative battery terminal. Briefly connect pin 1 to the positive battery terminal. Does the solenoid 'click'?
Yes success
No, renew canister purge solenoid

 

[mty12345]

Yeah with that fault code and negative fuel trims, i'd say 95% chance that's your issue. Would only really affect it at idle when vacuum is high, so all fits together

 

[michaelharrell]

That actually tells quite a bit, the fact you're getting misfires on all four cylinders suggests it's unlikely to be an ignition issue, as it's affecting the engine as a whole rather than one or two individual cylinders.

If it were a fuel pressure issue, I'd expect to see fuel pressure or mixture-related fault codes, and for the symptoms to become more noticeable under higher load and RPM, possibly accompanied by a lean condition. Likewise, if the valve timing were far enough out to cause consistent misfires, I'd normally expect to see cam/crank correlation or timing-related fault codes.

Since the misfires mainly occur at idle and low RPM, and there don't appear to be any other relevant fault codes, I'd be looking more towards a vacuum leak or PCV system fault.

I'd start with a visual inspection of all the vacuum hoses and the PCV system, followed by a smoke test if nothing obvious is found. I'd also have a look at the fuel trims, as they'll often point you essay checker in the right direction.

Could a faulty PCV valve really cause misfires on all four cylinders mainly at idle?