Strange problem Possible Injector issue?

[-J-]

Right my car developed a Missfire, one moment it was fine parked up and came back an hour later and it was missfiring.

So far i Have -

1 - Checked the Coil
2 - Checked the HT leads
3 - Checked the Spark Plugs
4 - Checked Injectors


Very strange... Counting Cylinders from Right to Left. Number 2 injector didnt seem to be firing, found this out by unclipping the injectors one by one. Cylinders 1,3&4 all made the engine labour when they were taken off, but number 3 made no difference so looks like its not working.

Next I took out the plugs, Number 2 Spark plug was filthy so cleaned it up and put it back into Cylinder 1.

Then I have checked the HT leads, Resistance readings between 6.12 and 5.12 on each lead.

Re-assembled the car and it seems to be running ok again but with a very small pop, pop from the exhaust at Idle speed (Im sure it was doing this before though), Number 2 Injector seems to be working again as well (I presume that the ECU must shut it down if there is a fault with plugs or something? Although I had no warning lights on)

Has anyone got any suggestions as to what could have caused this to happen? Im 99% sure its not resolved but just temp fixed and ill have to book it into Renault to be looked at.

 

[rctempire]

Have you had your timing belt done recently?

I remember on my clio we couldnt figure out why cylinder 3 wasnt firing after a head gasket was fixed. Turned out to be the tappet had tightend on the exhaust valve and the timing was 1 tooth out. Fixed timing and it got a bit better, checked all the clearances for the tapets, found problem out and away we went.

 

[-J-]

No The belt is still the original, its not due until Dec this year.

 

[ditz]

just because you unplug an injector and it makes no difference dosnt mean its the injector.

what about if you take that lead off the coil pack while its running, any difference in note?

it could be a compression issue..
i know you have said you have checked the coilpack ht leads and plugs but how have you gone about doing this as they are most common.

plug that injector back in, and put a long screwdriver to it and put your ear to that.. you should hear a nice crisp tick (listen to the others to compare)

 

[-J-]

Each of the leads has been taken off with engine running, As the lead comes off the coil the engine labours / cuts out.

They were then tested with a Fluke Meter at spark plug end to check resistance.

Each of the Injectors was unplugged one at a time and everyone caused the engine to drop a cylinder except number 2 which made no difference to the lumpy running?

Plugs have all been removed all were clean apart from number 2 which was Black with carbon so we cleaned it up and put into Cylinder 1 and the "Good Plug" from cylinder 1 into cylinder 2.

This seems to have improved greatly the running of the engine although something is still not 100% as im still getting a little pop, pop from exhaust on idle. I cant work out why the plug would have become more coked up than Amy Whinehouse on a Night out.

I cant see it being a compression issue as was fine driving it parked up for 20 min started it and there was the missfire, Would have thought lack of compression would have bought a warning light on?

What could cause loss of compression on an engine with only 18k on the clock? And what would the symptoms be as at about 3k revs + the engine runs as you would expect it to surely lack of compression would mean the car was down on 3 Cyl all the time?

 

[Clio1.6Rxe]

Each of the leads has been taken off with engine running, As the lead comes off the coil the engine labours / cuts out.

They were then tested with a Fluke Meter at spark plug end to check resistance.

Each of the Injectors was unplugged one at a time and everyone caused the engine to drop a cylinder except number 2 which made no difference to the lumpy running?

Plugs have all been removed all were clean apart from number 2 which was Black with carbon so we cleaned it up and put into Cylinder 1 and the "Good Plug" from cylinder 1 into cylinder 2.

This seems to have improved greatly the running of the engine although something is still not 100% as im still getting a little pop, pop from exhaust on idle. I cant work out why the plug would have become more coked up than Amy Whinehouse on a Night out.

I cant see it being a compression issue as was fine driving it parked up for 20 min started it and there was the missfire, Would have thought lack of compression would have bought a warning light on?

What could cause loss of compression on an engine with only 18k on the clock? And what would the symptoms be as at about 3k revs + the engine runs as you would expect it to surely lack of compression would mean the car was down on 3 Cyl all the time?

Is it running rich in cylinder 2? have you checked fuel filters + air filters + oil levels? just a thought...

 

[-J-]

Oil is ok, Air filter is a 3 month old K&N Gen 2 57i Fuel filter (Im not sure where it is) but its meant to be good for 150k miles so Renault say?

 

[Mike@Rentech]

easy swop the injector you suspect to be faulty to a different cyliner and if that cylinder starts to missfire you know its a faulty injector, they do fail and I have changed loads on all Renault models.

 

[-J-]

Thanks for that Mike Ill try swapping it and see what happens (Although the car seem to be running 98% as it should now I have cleaned the plug off)

 

[-J-]

Right the injector seems to be working ok now I have swapped the dirty plug into another cylinder.

Would the car have picked up that a plug was not working and shut an Injector down?

Why would the plug have become coked up so badly?

 

[-J-]

Just been out in the car again, Seems to have lost the missfire now but seems to be rough at Idle.

Its giving a very quiet pop noise every 3rd or 4th beat?

 

[NIN-172]

maybe one of the plugs is duff?
I've seen plugs that look perfectly fine from looking at them, but have been damaged & causing a problem.

I had some bosch plugs on an xr3i once which developed a missfire. Took them all out & cleaned (they were only a few months old), then went on to change virtually every other part on the engine (including, coil, leads, distributor, cam belt etc..). Then when it got really really bad I took the plugs out again to check for some reason & the inside of one of the plugs had fallen out

 

[-J-]

have found the plugs on Ebay for £7.50 each so think ill get a set and see whats going on... Cant hurt for £30

 

[-J-]

Right got mine back from Renault Watford - Carbon Build up in the Throttle body was causing the issue so they stripped it an cleaned it off and Its Purring again, So much Smoother!

They picked up on some other issues I will need to get done soon as well -

Front brake disks Lipped on inside and corroded.
Rear brake pads friction material breaking up.
Oil leak from gear Selector Seal
Dephaser pully noisey
And the Big one oil leak from Cam cover, this is a cambelt off job so as it needs doing soon it can wait until my car goes to Ren-Tec for the belt to be done... i just need to keep a very close eye on it as its near the belt where its leaking.

But Very Happy with what they have done and the car is running sweet again, And price wise not to bad £50 (Got it 1/2 Price)