Missfire on cylinder 3, new plugs, leads, coil and injector is working. Plug is black

[keithjames84@gmail.c]

Hi all I am having another missfire problem, I had one before christmas on cylinder 4 and it turned out to be a broken connector on the injector so i replaced the injector and all was fine.

as title i am having a missfire problem again , this time on cylinder 3. Thanks to the last misfire problem the car has new leads, plugs ,coil and i have rechecked the injectors and they are all spraying fuel.

The spark plug in Number 3 is almost completely black apart from the end of the electrode where the spark has been arching.

It also seems to be a bit of an intermittent fault, as the problem came last weekend but some how fixed itself till now and its back to 3 cylinders.

Any ideas at all, will be much appreciated. I got the car booked in at a garage on monday. But want to see if anyone else can think of anything that i may have missed?

Is it possible the spark timing could be out for just the third cylinder??

 

[keithjames84@gmail.c]

Re: Missfire on cylinder 3, new plugs, leads, coil and injector is working. Plug is b

is it possible for the ecu to forget to spark for the third cylinder but not the rest?

 

[regi james]

Re: Missfire on cylinder 3, new plugs, leads, coil and injector is working. Plug is b

i would have thought you would lose 1 and 3 as it works on wasted spark principle, could be injector or associated wiring fault

 

[sideways danny]

Re: Missfire on cylinder 3, new plugs, leads, coil and injector is working. Plug is b

i'd do a compression test to be sure, but it likely just needs a new set of leads and sparkplugs

 

[keithjames84@gmail.c]

Re: Missfire on cylinder 3, new plugs, leads, coil and injector is working. Plug is b

Yeah i am sure its an electrical problem as it seems the problem comes back with the wet weather. I was thinking it would effect 2 plugs if the coil was failing .

But it still is getting the signal for the second cylinder on that side of the coil.

Im just wondering if the ecu has somehow got damp, it could be effecting the signals for firing for just the third cylinder.
I looked up in a engine manual for this engine it puts out signals for 2,3 on one pin (number 1) and 1,4 on an other pin (number 32).
I can see the spark plug is sparking, but i think it maybe only for the 2nd cylinder pulse. Therefor if that theory is correct, as the firing order is 1324 the firing of the third cylinder is 180 degrees out . meaning if it ignited its going to ignite at low compression and have v poor combustion hence the dry black plug.

Still its going into garage tomorrow so should find out bit more.

 

[keithjames84@gmail.c]

Re: Missfire on cylinder 3, new plugs, leads, coil and injector is working. Plug is b

apart from looks like firing order is 1342 so kinda foils that theory lol think its time leave it 2 the mechanics

 

[regi james]

Re: Missfire on cylinder 3, new plugs, leads, coil and injector is working. Plug is b

take your engine cover off look under your bonnet with engine running and look for sparks from leads, i had this on mine ended up buying 2 sets of leads as non renault ones are shocking, also check the resistance of the ht leads

 

[damo2008]

Re: Missfire on cylinder 3, new plugs, leads, coil and injector is working. Plug is b

mine was doing this on cylinder 3 the lead on cylinder 3 was still sparking
but when under load it wasnt sparking turns out it was a faulty ht lead

 

[keithjames84@gmail.c]

Re: Missfire on cylinder 3, new plugs, leads, coil and injector is working. Plug is b

Hi guys got it back from the garage. They could not diagnose a fault still charged me 50 quid though.

They said the ecu was filled with fult codes. There was to many to make a diagnoses apparently. What did keep coming up was apparently "CAT damage".

They have cleared the ECU and said to run it few hundred miles and bring it back if the engine warning light comes on.

However now i have it back it is currently not misfiring as such. Its just got a terrible lumpy idle and seems to be just not misfiring( more lumpy then usual). Its hunting for ignition on idle and when you rev it you can hear a cylinder is struggling through out the speed range. When driving around under load and through acceleration it feels fine at the moment.

Is it possible the large number of fault codes in the ECU could have caused the ECU to malfunction so it stopped firing properly ?

Im having a horrible feeling the main problem is looking like exhaust valve problems

 

[keithjames84@gmail.c]

Re: Missfire on cylinder 3, new plugs, leads, coil and injector is working. Plug is b

I think i may go get some new renault leads. As i put the old ones back on before i took it to the garage. That combined with the clearing of fault codes is the only difference that has happened to make the misfire less severe.

 

[keithjames84@gmail.c]

Re: Missfire on cylinder 3, new plugs, leads, coil and injector is working. Plug is b

just wish i could get a positive diagnosis on something so I dont keep wasting money buying parts till something changes.

 

[keithjames84@gmail.c]

Re: Missfire on cylinder 3, new plugs, leads, coil and injector is working. Plug is b

It Idle it also smells of rotten eggs . This is a new problem

 

[regi james]

Re: Missfire on cylinder 3, new plugs, leads, coil and injector is working. Plug is b

it smells of rotten eggs (sulpher) because it is misfiring, i would try a new set of renault leads, they are not cheap though approx £100

 

[oVerboost.]

Re: Missfire on cylinder 3, new plugs, leads, coil and injector is working. Plug is b

Hate to mention it, but my 172 had a similar problem, and that turned out to be a damaged piston. I am still waiting for the car to come back from the stupidly slow garage doing the work.

It could be an injector, exhaust valve or a wiring fault.

Hope its nothing too costly/troublesome.

 

[sideways danny]

Re: Missfire on cylinder 3, new plugs, leads, coil and injector is working. Plug is b

did you do the compression test i suggested at the top of the thread?

 

[keithjames84@gmail.c]

Re: Missfire on cylinder 3, new plugs, leads, coil and injector is working. Plug is b

hopefully sometime this week , i chap at the garage said he was going do it, but said its a difficult job on this engine so if i want it doing is another 75 quid. Borrowing a compression tester soon so hopefully can rule it out.

Ran the car for a bit over the weekend and took it back to the garage to see if they can try continue there diagnosis. But the ECU has no relevant fault codes just something to do with intermittent brake sensor.

It seems to run fine if its under load its just at idle or no load conditions that its hunting for ignition, it is firing just very lumpy. The garage seem to think its something to do with the thermostat. It was taking for ever to warm up and was only at 72 degrees C according to the ECU.

Just want to try rule out a few things :

If the MAP sensor is still working, just not working correctly would that come up with a fault code ? same with the lambda sensors if that was working incorrectly would it have a fault code ?
my emissions warming light is not coming on does that mean the AFR is not to far from ok?

 

[keithjames84@gmail.c]

Re: Missfire on cylinder 3, new plugs, leads, coil and injector is working. Plug is b

compression test done cyl1 = 192 psi , cyl2=190psi, cyl3 = 195psi, cyl4=191psi . so no horrible differences. Does these results sound ok ?

 

[keithjames84@gmail.c]

Re: Missfire on cylinder 3, new plugs, leads, coil and injector is working. Plug is b

have also just done a vacuum test on the manifold, at idle the vacuum seems to be about 40-42 cm Hg vac. I think it should be higher then this. 45 to 55. Although i do not know so any input on this would be much appreciated!! Also where does the vacuum hose go to that is connected just after the throttle body on the intake manifold? It seems to disappear under the air filter box.

 

[regi james]

Re: Missfire on cylinder 3, new plugs, leads, coil and injector is working. Plug is b

think that goes to acoustic valve, compression seems ok, if youve had upper inlet manifold off check the gasket is mating properly

 

[Sean6545]

Re: Missfire on cylinder 3, new plugs, leads, coil and injector is working. Plug is b

Was there any moisture/water/brown staining on the HT leads when you did the compressions?

 

[keithjames84@gmail.c]

Re: Missfire on cylinder 3, new plugs, leads, coil and injector is working. Plug is b

just ordered a new inlet manifold gasket and injector seal kit today , just make sure that they are all sealed as best as possible. HT leads looked fine. After i have fitted these new bits. I think i am going have to take it to a dealer. See if they are any better at diagnosing then the last garage.

 

[keithjames84@gmail.c]

Re: Missfire on cylinder 3, new plugs, leads, coil and injector is working. Plug is b

Ok think i have found the problem this evening . As the compression ratio is ok, the spark plugs are fine the coil is fine and the leads are ok. It leaves me to believe its fueling.

As only one spark plug is showing signs of problematic combustion, and there are no sensor fault codes coming up in the ECU. It leads me to believe its cylinder specific fueling problem, not caused by over fueling due to trying to compensate for bad sensor reading as that would effect all cylinders.

So this leaves the injector, and the ECU. I had the injector out before to see if it was spraying and it was, but by how much compared to others i have no idea.

So from this I have swopped the injector from the problem cylinder3 to cylinder1 that was working fine. If the incomplete combustion moves cylinder its the injector thats the problem if the problem remains at cylinder3 its the ECU sending out to long a pulse width.

Turns out after ten mins of running problem of bad idle still present. check the spark plugs again and the cylinder3 plug is starting to clean up and the cylinder1 plug is starting to carbon up. Therefor i believe the problem is the injector is leaking or over-fueling for what ever reason. so placed a order with renault for a new one . will post if it solves the problem . maybe useful someone in the future.

 

[keithjames84@gmail.c]

Re: Missfire on cylinder 3, new plugs, leads, coil and injector is working. Plug is b

Ok changed the injector , drove 200 miles . All the spark plugs now look like clean and as if the engine is firing correctly.

However there is still when on idle and through out the rev range a hunting for ignition.

when i took the manifold off it seemed to have a film of oil all over the inside. There also was rings of oil around the manifold gasket where they two halfs join and overlap slightly.

When taking the manifold off there is a short thick alloy tube coming up form the cam cover. This enters the bottom of the manifold. What is this for and what does it do. ?

 

[Huffski]

Re: Missfire on cylinder 3, new plugs, leads, coil and injector is working. Plug is b

This has been an interesting read mate. My car at the moment has the exact same problem on the exact same cylinder. So far I have changed leads and coil pack and I'm doing spark plugs tomorrow. If this fails I'm gonna try tdc sensor failing this injectors and failing that ecu but it's early days ATM. How much your injector cost you? Cheers

 

[Daytime172]

Re: Missfire on cylinder 3, new plugs, leads, coil and injector is working. Plug is b

I'm having the same problem on mine as its hunting on idle.

so ive just replaced the coil pack and gave the plugs a clean up but nothing has changed so may take mine to a garage for them to have a look at.

 

[motorbikingbleu1]

Re: Missfire on cylinder 3, new plugs, leads, coil and injector is working. Plug is b

Hi any update on these? I've had a very similar problem. hit 3 cylinders, replaced HT leads and plugs, no difference, replaced 2nd injector, ran a little better, still lumpy on idle and when under load.. if I'm gentle with the gas it runs sweet? guy in the garage gave me a massive list of error codes same as you. all sorts of sensors and failures. replaced the coil pack, got rid of the EML light, not scanned it since but its still running lumpy.. did you have any luck finding a resolution?

 

[I_scoff_cake]

Re: Missfire on cylinder 3, new plugs, leads, coil and injector is working. Plug is b

Just wondered if it could be an earthing problem?

 

[motorbikingbleu1]

Re: Missfire on cylinder 3, new plugs, leads, coil and injector is working. Plug is b

Hmm.. where do I start with an earthing problem!? Car runs fine when cold (for approx 2 mins) And at some points when driving it (not under load, real gentle acceleration)

 

[Modgiz]

I had the problem on cylinder 4 a real sooty spark plug all the others were fine, I had previously replaced the 02 & co2 Lamda sensors and the Cat but still high on emissions,

my mates stripped the top block down and noticed a sticking intake valve so all have been replaced and all cleaned down l, it's going in Monday for emissions testing again so I'll update you when I know

 

[Chris_Beer]

@Davyy is the expert here people