The distributor is firing the other 3 remaining spark cars ok which means the problem is in the distributor at the contact point of spark plug no 3 or after the distributor i.e spark plug no 3 high tension lead or spark plug no.3 itself. The distributor recieves a single high tension voltage from the coil and distributes it to the 4 spark plugs. Have you tried a new high tension lead for cylinder number 3?

 

Thanks for the reply.

It gets a good spark at number 3 plug anyway so i think the issue is more fuelling related which is why im wondering if the cam sensor could be at fault

 

Cam sensor is dead if it won't run with the crank sensor disconnected. However this won't cause a misfire. Disconnect it for now to avoid any confusion.

Do a compression test to prove there is nothing nasty going on in that cylinder. Is the plug the same colour as the others?

Have you swapped the plug around to see if the fault follows the plug. If not then suspect the lead.

 

The plug is a different colour to the rest.

I cleaned them all, put them back in and went for a run. When i got back i took them all out and they all were brown apart from number 3 which was still very clean and dry but still sparks fine.

I then cleaned them all again and swapped number 3 plug with number 1 and again just number 3 stayed clean

I will do a compression test now and post results

 

Just done compression test 170 on every cylinder so theirs no problems there.

So does it looks like a fuelling issue? Is there any other sensors that could cause this?

 

Never heard of a injector failure on here at least (maybe someone has) and don't see how ECU (software?) would ever fail to send a signal to just 1 out of 4.
Next action would be a.Check wire / connector condition onto the injector, again assume you can put LED? or similar in place to check receiving signal and b. Check injector (I'm never done it, and don't have expected readings, I assume you can check resistance across terms*) Maybe someone more knowledgeable or specific practical experience can post exact procedure possible. You don't really want to be swapping injectors unnecessary do you ?
170 across all then, very good.

 

This morning i took the injectors out and swapped 3 and 4 over. still misfiring on 3 so i tested each injector connection and there was no power to number 3 injector!!

After chasing the wire back to the ecu i noticed the pin connection to the ecu was loose. I pushed it back in and now have power to all injectors

I didnt change the O rings on the injectors so after taking them out and putting them in twice i think they have lost their seal because its misfiring on 3 and 4 now and it was making a tapping noise, also the idle is much higher and when you rev it, it backfires. but i still have power to all injectors

Does this sound normal for when injector seals fail? i've herd of injector knock and i guess the high idle is due to air getting in past the seal maybe?

I've been quoted £36 for the o rings which seems very steep to me. Where can i get them cheaper?

 

Good progress . It is advisable to renew seals, gaskets and O-rings whenever they are disturbed.

 

It's always a relief when your thinking the worst and it's something simple!!

I've pulled them all out again and a couple of O rings have split so I've ordered a full set and a new manifold gasket. Let's see if this fixes it!