diagnosing misfiring cyclinder ideas?

[jamei303]

Engine is Ecoboost 1.0L 3 cylinder. Engine management light came on and I read the code as P0302 - misfiring cylinder 2

Still under warranty so:

- dealer replaced cylinder 2 spark plug - it happened again
- dealer swapped coil packs on 2 and 3 to try and eliminate that - engine ran fine for six months
- at the annual service, dealer replaced all spark plugs as service item - after first long journey the management light comes back for cylinder 2 misfire again

There are three weeks left on the warranty so I am going to take it to the dealer again, but I wonder if there are any clues here? Why would swapping the coil packs seemingly resolve it, and why would new spark plugs kick it off again?

[Greenbot35]

Compression test might be useful for checking valves and hgf issues.

[Gad-Westy]

When you say that the dealer swapped coil packs on 2 and 3, do you mean moved coil pack from 2 to 3 and 3's to 2 or replaced both with new ones?

If it's the former, it would seem quite plausible that there is a coil pack problem and new ones are needed. It's not uncommon on modern cars for coil packs to fail. I'm surprised they're even bothering messing around with spark plugs.

[jamei303]

Gad-Westy said:

When you say that the dealer swapped coil packs on 2 and 3, do you mean moved coil pack from 2 to 3 and 3's to 2 or replaced both with new ones?

If it's the former, it would seem quite plausible that there is a coil pack problem and new ones are needed. It's not uncommon on modern cars for coil packs to fail. I'm surprised they're even bothering messing around with spark plugs.

They swapped 2 with 3 and vice versa.

As cylinder 2 is still the problem one, this would seem to eliminate a coil pack problem?

[stevieturbo]

Well ecu diagnostics have already told them which cylinder.

Compression test, check fuel, check spark, check wiring...very basic stuff.

And are there any other symptoms of problems ? losing water or anything ?

[227bhp]

Maybe when it went in the second time they swapped it back to how it was originally.

[Mignon]

Try reducing the spark plug gap a bit. Too big a gap is a common cause of misfires on turbo engines.

[chammyman]

They are most likely trying to get you to wait out the 3 weeks left on the warranty.

Chances are it needs an engine. They are throw away garbage.

[stevensdrs]

So it was running fine for 6 months until they changed the plugs. In order to change the plugs they will have dislodged a lead or coil pack re introducing the fault. Something is leaking the HT somewhere.

[Classy6]

jamei303 said:

They swapped 2 with 3 and vice versa.

As cylinder 2 is still the problem one, this would seem to eliminate a coil pack problem?

Yes, exactly. If the misfire came back on cylinder 3, it would of meant coilpack number 3 [2] was faulty. However it came back on cylinder 2, so would indicate coilpack & plug (you mentioned it's been changed) are actually OK.

Time for them to start looking elsewhere.

[jamei303]

OK so the no.2 spark plug was cracked, again. This'll now be replaced with what will be the fourth spark plug on the no.2 cylinder in a year.

If this was being caused by a problem with the engine rather than installer error, could this happen without other fault codes being generated e.g. knocking, coolant temp, fuel mix etc?

It's the six months with no trouble that has me confused.

Edited by jamei303 on Monday 19th February 10:25

[GreenV8S]

jamei303 said:

OK so the no.2 spark plug was cracked, again.

Was this a crack through the ceramic on the external part of the plug?

[010101]

It is doubtful that the computer would be able to sense the HV side of the the coil. Silicon ICs really don't like high voltages!
It is likely on the low voltage side.

[GUSFERLUS]

jamei303 said:

OK so the no.2 spark plug was cracked, again. This'll now be replaced with what will be the fourth spark plug on the no.2 cylinder in a year.

If this was being caused by a problem with the engine rather than installer error, could this happen without other fault codes being generated e.g. knocking, coolant temp, fuel mix etc?

It's the six months with no trouble that has me confused.

Edited by jamei303 on Monday 19th February 10:25

Hi did you ever resolve this?

[jamei303]

GUSFERLUS said:

Hi did you ever resolve this?

Yes I sold it quickly before it happened again