Mystifying Seat Ibiza MK4 1.2 misfire [SOLVED]

[Aokuan]

Hello everyone,

I've been looking over this forum for the issue I'm experiencing and haven't found a possible solution to the misfire problem I'm having with my Seat Ibiza 1.2 Reference Sport 2007, the issue started out with the car engine management light blinking when travelling on the motorway, this would occur randomly and the car would go into limp mode. However recently it has become more consistent and it always appears to be the same cylinder misfiring, here are the tests I've carried out this far

Checked Coil Pack - OK
Changed Spark plug - OK
Changed fuel injector - OK
Compression test - all cylinders on equal PSI

Despite the current testing the misfire always occurs on the same cylinder
P0303

The car has only done 44k miles..

If anyone can provide me some assistance on the issue.. or if anyone has experienced a similar fault with a fix I would greatly appreciate the help!

Cheers

 

[RUM4MO]

Does this not just leave a wiring problem?

If that car has COP, did you swop coils between cylinders, same for injector?

 

[Aokuan]

I did indeed swop coils between cylinders, and the same for the injector. What is it you mean by COP? I'll check the earthing today and report back to see if it has cured the problem.

Cheers

 

[RUM4MO]

You have clarified "COP" by saying that you swopped coils, COP = Coil On Plug.

Any wiring issues sound like they are intermittent, though maybe a "wiggle" test would make that fault permanent! Have you found any reports of wiring loom issues with that age and model of car with that engine, either coil or injector wiring loom issues?

Edit:- maybe a horrible or discouraging thing to say, that any wiring issue could be anywhere back to the engine ECU, I've even read about a bolt that is considered too long sticking up and puncturing part of the wiring harness, after that it might even be an intermittent engine ECU output stage fault? You can get ECUs tested if it ends up that that is what you are driven to do!

Another Edit:- just to add, I have absolutely no experience with this engine version.

 

[turbod]

I had a similar problem with a Audi s8 recently and the problem turned out to be a faulty ignition control module, basically a small electrical box feeding the ignition coils, a bit like an amplifier for the signal for the ignition coils, they break down inside and stop sending a signal to that particular coil, follow the wires back from the coil and it will lead you to them, on the s8 they were mounted near the airbox there will probably be two modules then you just need to figure out which one is knackered by resistance testing from the earth pin to each output signal connection

 

[RUM4MO]

@turbod, it would be very handy if that was the case, but, I think with these cheaper cars, all that is bundled up inside the engine ECU, so no "interface" to get messed up by the coils - just the ECU, which is cheaper in production, but a bit of a wallet wrecker later on in life!

 

[turbod]

@rum4mo they definitely have them on the earlier models and there are some listed on ebay for seats so hopefully this is the case with this car fingers crossed for the guy

 

[Aokuan]

After trying to diagnose the issue for a few days now, still no avail.. unfortunately there is no ignition control module on the Mk4 ibizas so it cannot be one of the issues, thank you for the suggestion regardless.
When I performed the compression test I was recieving results from all cylinders at 11bar, which shouldn't be the issue as cylinder 1 is not misfiring.
My thoughts is that the timing chain has possibly stretched or the tensioner/guide rails are worn causing the timing to be off for cylinders 2 and 3, although I would imagine this would effect all 3 cylinders. What are your thoughts on this?
I've messed with the wiring to see if I can cause the engine to act differently whilst poking around, no positive clues however..
ECU testing is ideally the last resort, but still remains a possibility.
I'm having problems with both cylinders 2 and 3, I was hoping if I replaced all 3 coil packs and spark plugs it would cure the issue, but still there is no cure.. I'm stumped

Cheers

 

[turbod]

Could it be a cam / crank position sensor starting to fail ? If that's the case though you think you'd have a error code ? If the timing chain had jumped / stretched the timing would be out on all cylinders...... What about a live data scan at a good auto diagnostic place ?

 

[chrisRibiza]

Random one but are all the brake lights working correctly?

If a bulb goes out on the MK4 Ibiza it can cause the car to lose power etc.

 

[Aokuan]

@turbod Yes I do believe if the cam/crank position sensor was out it would flag as an error code and all cylinders would be misfiring and indeed the stretched timing chain would mean all cylinders would be missing.. it has to be a problem with the electrics/ignition.

@chrisRibiza I'll have to look into it as I haven't checked, thank you!

 

[turbod]

Just had a thought pal, one of the cars in our household had an intermittent fault with the switch wire going from the alternator plug to the ecu giving bad continuity causing the alternator to not charge the battery and the cause was a corroded wire, because the screen wash pipe which is taped inside the loom was leaking causing a chafed wire inside the loom to break down.....
The wiring in question runs along the n/s chassis leg..... The fix involved continuity testing the suspect wires from the alternator plug back to the ecu multi plug connector and replacing a section, and also running two new sections of screen wash pipe from the screen wash bottle outside the loom preventing future water ingress.

You could do similar but obviously with the i/c wiring from the plug back to the ecu plug, this will rule out the wiring

 

[turbod]

Just had a thought pal, one of the cars in our household had an intermittent fault with the switch wire going from the alternator plug to the ecu giving bad continuity causing the alternator to not charge the battery and the cause was a corroded wire, because the screen wash pipe which is taped inside the loom was leaking causing a chafed wire inside the loom to break down.....
The wiring in question runs along the n/s chassis leg..... The fix involved continuity testing the suspect wires from the alternator plug back to the ecu multi plug connector and replacing a section, and also running two new sections of screen wash pipe from the screen wash bottle outside the loom preventing future water ingress.

You could do similar but obviously with the i/c wiring from the plug back to the ecu plug, this will rule out the wiring

 

[Sprabu]

@turbod Yes I do believe if the cam/crank position sensor was out it would flag as an error code and all cylinders would be misfiring and indeed the stretched timing chain would mean all cylinders would be missing.. it has to be a problem with the electrics/ignition.

@chrisRibiza I'll have to look into it as I haven't checked, thank you!

@Aokuan, Did you get the problem sorted out? What was the actual problem? Can you please let me know, I am also getting similar misfire problem

Regards,
Saravana

 

[Aokuan]

@Aokuan, Did you get the problem sorted out? What was the actual problem? Can you please let me know, I am also getting similar misfire problem

Regards,
Saravana

@Sprabu

I haven't had any luck with the suggestions from this forum post so far, I'd given up for a while and was switching the ignition off on the motorway to the first position and back to ignition (important to not switch completely since I don't want the steering wheel to lock up) whilst still rolling, this meant I could clear the ECU fault quickly without stopping. This is dangerous however as my lights go out in the dark and people are wondering what I'm doing, whilst leaving me travelling at 70mph into pure abyss as of now its got worse but compression testing still remains to have 150psi on each cylinder and all of the other checks I've carried out so far seem to be fine.

I've done some research into the matter however and I'm starting to believe its the PCV valve thats broken allowing oil to foul the cylinder or causing the air mixture to be too rich thus causing misfire. The PCV valve ventilation pipe is connected to the intake manifold next to cylinder 3 leading me to believe it is the cause. I'll let you know how it goes once I do some investigating. I'm currently in the process of also replacing the timing chain as I believe it may have become stretched and caused the timing to be slightly off. I'll remove the intake manifold and check for any fouling of the valves.

Regards,
Aokuan

 

[Sprabu]

@Sprabu

I haven't had any luck with the suggestions from this forum post so far, I'd given up for a while and was switching the ignition off on the motorway to the first position and back to ignition (important to not switch completely since I don't want the steering wheel to lock up) whilst still rolling, this meant I could clear the ECU fault quickly without stopping. This is dangerous however as my lights go out in the dark and people are wondering what I'm doing, whilst leaving me travelling at 70mph into pure abyss as of now its got worse but compression testing still remains to have 150psi on each cylinder and all of the other checks I've carried out so far seem to be fine.

I've done some research into the matter however and I'm starting to believe its the PCV valve thats broken allowing oil to foul the cylinder or causing the air mixture to be too rich thus causing misfire. The PCV valve ventilation pipe is connected to the intake manifold next to cylinder 3 leading me to believe it is the cause. I'll let you know how it goes once I do some investigating. I'm currently in the process of also replacing the timing chain as I believe it may have become stretched and caused the timing to be slightly off. I'll remove the intake manifold and check for any fouling of the valves.

Regards,
Aokuan

Thanks for update Aokaun, My car showing P301 error which is related to Cam shaft sensor. I am also investigating what might be the problem, I will also let you if any update on my car. Please let me know once you investigate the problem.

 

[Sprabu]

Hi Aokuan,

I am also in same situation like you, I checked with one of the garage they told they suspect this might be timing chain problem (jumped/stretched), I have booked appointment on coming Tuesday to do the same.

Can you please let me know any update on your case? It might help me in my case.

Regards,
Saravana

@Sprabu

I haven't had any luck with the suggestions from this forum post so far, I'd given up for a while and was switching the ignition off on the motorway to the first position and back to ignition (important to not switch completely since I don't want the steering wheel to lock up) whilst still rolling, this meant I could clear the ECU fault quickly without stopping. This is dangerous however as my lights go out in the dark and people are wondering what I'm doing, whilst leaving me travelling at 70mph into pure abyss as of now its got worse but compression testing still remains to have 150psi on each cylinder and all of the other checks I've carried out so far seem to be fine.

I've done some research into the matter however and I'm starting to believe its the PCV valve thats broken allowing oil to foul the cylinder or causing the air mixture to be too rich thus causing misfire. The PCV valve ventilation pipe is connected to the intake manifold next to cylinder 3 leading me to believe it is the cause. I'll let you know how it goes once I do some investigating. I'm currently in the process of also replacing the timing chain as I believe it may have become stretched and caused the timing to be slightly off. I'll remove the intake manifold and check for any fouling of the valves.

Regards,
Aokuan

 

[Aokuan]

Hi Aokuan,

I am also in same situation like you, I checked with one of the garage they told they suspect this might be timing chain problem (jumped/stretched), I have booked appointment on coming Tuesday to do the same.

Can you please let me know any update on your case? It might help me in my case.

Regards,
Saravana

Hi Saravana,

I got done with fitting a new timing chain and tensioner I also got the cylinder head refurbished with new valves, valve guides and seals. Unfortunately the problem is still there. What I recommend doing to check your timing is out is taking the camshaft caps off on the right hand side of the engine to check if both cams are in time. This may help you confirm if the chain has stretched/jumped. If the garage has the timing tools at hand they can confirm it for you, rather than getting it changed and having no success. They will need the timing locking tools to check this, two are inserted where the cam caps are once those are removed, this is on the far top right hand side of the engine when viewing from the front. And the other is a crankshaft timing tool that fits in place of the crankshaft speed sensor. If all of these tools can be in place, your timing chain has not stretched/jumped. This would not take the garage long to do if they have the tools at hand. If they don't have the tools at hand I recommend checking in at another garage who can check the timing this way for you.
Good luck!

Regards,
Aokuan

 

[Sprabu]

Hi Aokuan,

They checked the timing chain today and they told timing is OK and it might be problem with cylinder head/valves. Garage person told it will take time and money(around 700-800£), So I told not to do the same. I am not sure now if really problem with Engine or wiring for Cam sensor.

I came back home and with my friend help just did some try to check whether CAM sensor working or not. We removed CAM sensor wiring and run the engine, it still runs same way no difference. We are thinking it might be problem with CAM sensor wiring. We tried checking voltage in Multi meter ( The connection coming from ECU) it shows 5V in 2 pins, looks different ( we were thinking only one pin should show 5V) other pin should be 0. We are thinking may be CAM sensor wire shorted/damaged in between the way going to ECU.

We want circuit diagram/pin configuration to check that. We are trying to find the same now.

Regards,
Saravana

 

[leo5566]

whats your engine code i will try get you some pin outs