P0300 Misfire.....Here we go again!

[Sir Nancy Flowers]

Hi all,

I know this topic has been covered again and again but I hope to cover this issue in a little more detail than the others....with your help!

I've got the usual flashing engine management light at idle and now whilst driving. The main culprits are Injectors, Coil Pack or HT Leads.

Here's where I'm at so far : I have removed the spark plugs and cylinder 3 (2nd in from the drivers side) is all sooty whereas the rest seem ok. Used but ok. Initially I thought the injector would be to blame but I've since tested the resistance and its showing 14ohms. Perfectly acceptable.

Next on the hit list was the HT leads. After some learning, I learnt that the leads should be showing a number of thousand ohms per foot. Mine, some red aftermarket one, shows approximately 500 ohms per foot. Is this normal?

My next culprit is the coil pack but this looks relatively new truth be told. Any suggestions are helpful.

TIA

 

[JamesBryan]

99% it's an injector.

Resistance test won't show if it's full working potential. It could be blocked or anything.

 

[Sir Nancy Flowers]

Well that's reassuring. I've got 8 injectors (4 off the car on a spare rail). Think its worth switching one or two around?

Should I soak or clean them before trying?

 

[Ol’ Tarby]

Well that's reassuring. I've got 8 injectors (4 off the car on a spare rail). Think its worth switching one or two around?

Should I soak or clean them before trying?

Get them ultrasonically cleaned. @dann2707 used to do em, not sure if he still does or not

 

[Sir Nancy Flowers]

I'll test that tomorrow and report back. Thanks guys. Was about to start throwing parts at it 😂

 

[bloke]

it is an injector, ultrasonic cleaning doesn't help when it's an electrical issue with the injector.

 

[Ol’ Tarby]

it is an injector, ultrasonic cleaning doesn't help when it's an electrical issue with the injector.

My response was more to his "soak or clean" question

 

[dann2707]

Get them ultrasonically cleaned. @dann2707 used to do em, not sure if he still does or not

Thanks mate. Yes I can still do them, £30 for 4 including returned postage.

Had some cracking results

 

[Sir Nancy Flowers]

I agree that, if it is the injector, which all evidence suggests it is, cleaning it wont help. But. Cleaning the good ones sounds like a great idea!

 

[Sir Nancy Flowers]

Okay. Update. I swapped the injector for another one I had (used). Reassembled the inlet manifold etc etc. Started up fine. After idling for a bit, I checked the fault codes and it's still showing the fault code. Still feels like its misfiring too.

Any other suggestions?

 

[JamesBryan]

What makes you think it's just one cylinder or if you've even replaced the correct one?

 

[Sir Nancy Flowers]

Well that is a good point. Perhaps I'm wrong but judging by the state of 1 of the spark plugs, I assumed it to be cylinder 3. So that's the injector I changed.

 

[JamesBryan]

Never wise to guess on these 😂

I take it you know the order of the cylinders on these?

4 - 3 - 2 - 1 as you look from the front.

 

[Sir Nancy Flowers]

You're not wrong 😂.

Yes, I've got the ordering of things right. Luckily the leads were labelled which confirmed my googling!

 

[JamesBryan]

I'd just change them all if you have enough spares.

 

[Sir Nancy Flowers]

The issue is they're all used. I bought a rail with injectors about 6 months ago to try and cure this. Obviously it didnt work. My thinking is that it's not injector related. I changed all 4 6 months ago which didnt do a lot. The coil pack and leads haven't changed but again, that's process of elimination and there's no specific evidence to suggest its them. The leads are aftermarket and are labelled 'Formula Power'. Could they be the culprit?

 

[Rojer]

New OEM injectors are generally around £30/35 each so might be best just to get some new ones that you know are good.

 

[Sir Nancy Flowers]

I was quoted £58 per injector!

 

[Rojer]

Depends what deals and who you get them from. Even going onto Euro Car Parts just now and using their discount code it comes to £46. If you know someone in the trade or do enough digging you will get them cheaper.

 

[JamesBryan]

Renparts do them fairly cheap HERE

 

[Rojer]

£28

Here https://www.autodoc.co.uk/magneti-marelli/1858040

 

[Sir Nancy Flowers]

Anyone else? 😂.

The general consensus is that its injectors then. Looks like I'll be ordering some!

 

[william84]

Take the rail off and crank the engine to see if there is a noticeable difference with the injectors spraying pattern.
2 people required one cranking one watching.

 

[JamesBryan]

Take the rail off and crank the engine to see if there is a noticeable difference with the injectors spraying pattern.
2 people required one cranking one watching.

And one watching for the fire.

 

[william84]

And one watching for the fire.

I should of said take plug off coil as car may run on fumes.

 

[Sir Nancy Flowers]

So, just for clarification, I'm looking for an equal spray pattern. Should be a similar volume to the rest and not squirting..more spraying (pun intended). Is that right?

 

[Simon998]

I rigged up 4 x 500ml coke bottles with a bit of gaffer tape and put the injector tips into them, got someone to crank the car and check which bottle has the least fluid in it afterwards.

It was the only way I could think of doing it without getting fuel everywhere. This was on my 106 Rallyé but I imagine it would work with the clio also.

 

[Rojer]

What i would do is take the rail out, put the injectors into some bottles or put the rail in a bowl or something that doesn't spray fuel all over the engine, whilst still attached to the rail (if you can). Have someone crank the car and watch the spray pattern.

 

[Simon998]

lol Rojer, great minds.

 

[Sir Nancy Flowers]

Well. 2 posts saying very similar things at the same time. Creepy.

I'll give that a shot to be honest. Sounds like a plan

 

[Rojer]

Worst case £28 for an injector isn't going to break the bank.

 

[Sir Nancy Flowers]

For sure. £28 is the best option. Leads and the coil pack are both at least £50. I'll give that a test and see how we go. If they all spray fine, we know it's one of the other two

 

[Simon998]

Remember to pull the plug to the coilpack

 

[Rojer]

Would recommend getting good quality/OEM coil packs and leads as the cheaper ones are rubbish!

 

[Sir Nancy Flowers]

The coil pack looks oem but the leads say 'Formula Power' on them and are red. Anyone know of these?

 

[bloke]

Means sod all if they spray on cranking.

Clear codes, check resistance, run car until light pops on, read codes, look at freeze frame data and then hand in pocket and buy new injectors. Not worth messing roumd with used ones that might be ok.

 

[Sir Nancy Flowers]

Means sod all if they spray on cranking.

Clear codes, check resistance, run car until light pops on, read codes, look at freeze frame data and then hand in pocket and buy new injectors. Not worth messing roumd with used ones that might be ok.

When you say freeze frame data, what are you referring to? I have the usual cheapie obd scanner but that's all

 

[Rojer]

Means sod all if they spray on cranking.

Clear codes, check resistance, run car until light pops on, read codes, look at freeze frame data and then hand in pocket and buy new injectors. Not worth messing roumd with used ones that might be ok.

Surely if there is an issue inside the injector and it doesn't spray then you know it's gone so still worth checking with a spray test, but check resistance would be the quickest and easiest way.

 

[Sir Nancy Flowers]

I've checked the resistance against all the injectors and they're all showing between 14 and 15 ohms so no issue there. My only thought if it was blocked?

 

[Rojer]

If the resistance is within spec, and you have noticed that one plug is different from the rest then to me at least it points to an ignition issue if you have some random crappy HT leads then get them swapped over and check again.