The fault codes don't help much on these engines when it comes to a misfire such as Jane has.   She's doing the obvious basic items first which the right way to go about, I know because I had the same motor and the same problem sometime ago. In the end my problem was the  HT leads & pre-cat lambda sensor, was going suggest that next should the misfire persist.

Well, that proves that the code reader is about as much use as a chocolate fireguard (maybe less since you can eat the fireguard?  ), and everyone seems to be converging on the same main systems as being the issue based on experience.

Tbh the leads looked original, obviously unless the previous owner was a fool and bought from Renault but certainly didt look recent.

 

Yeah code readers normally just tell you what you already know..multiple misfire, well i never, i thought it was the radio causing it...

 

But anyways all the good the code reader is wouldt it of flagged up O2 sensor if it was faulty or are they known not to do this?

would have showed a complete failure of an item but not the intermittent problems as you have.

Right...im going to burn it!!!

 

Put new plugs, leads on today, new gaskets, bolted it all back together, still on 3 cylinders :(

 

AND THEN tweek the HT leads (they looked tight, forgot to turn them on the 90 degree) fire it up..its on 2 cylinders WTF!!!

 

I am literally at a loss..

Jane, are you absolutely sure the HT leads are in the right order?     The coil terminals are numbered, and I'm almost sure the cylinders number from the gearbox end on the F4R which is the opposite off all other cars.

If thats OK then you'll have to make sure the 2 faulty plugs are sparking. You will have to remove one of the plugs and HT lead from under the manifold, replace the manifold and with well insulated pliers or gloves hold the body of the spark plug against the metal part of the engine, not the tip of the spark plug.  Have an assistant start the engine and see if you get sparks.

Next thing to check is if the injector wiring is secure and they are spraying petrol although you will probably have to get a garage to check this for you.

As Bernie says, Renault have slung in one of their stupid "tweaks" in cylinder numbering order!

 

If it was on 3, I'd suggest replacing each plug in turn with one of the old set and see if it cleared, and then repeat with the leads since it wouldn't be the first time I'd seen a new bad plug or lead (the first time it confused the best mechanic I've ever known (not Briskodan)).

Jaguar number them in reverse as well.

Dont worry soot1e the plug test is next thing in order but yes they are correctly wired in, your right, the coil pack as corresponding number to correct lead, the OEM ones have the cylinder number on them but the new ones dont, simple case of take on off, compare and replace with new.

 

we're going to remove injectors after we know the plugs are firing, it could possibly be the signal wire as the 2 cylinders failing are the ones that fire together on the wasted spark system. 

 

Thankfully the injectors are only £40 each (whereas VAG's cost £130+ each) so although it unexpected expenditure it wont break the bank as much as i feared.

 

To be honest i dont think it is injectors, to me i have a gut feeling its wiring breaking down as over the past week its gone from 4 cylinders to 3, back to 4 then 3 again and now 2..in my opinion if an injector is blocked it would stayed blocked and not move across the board. 

 

i know it is possible but would a compression test be as simple as im thinking? With the manifold being in the way its not a simple case of remove spark plug and crank..

Slow progress eh, due to your work I guess.

Yes, it's a bit tricky doing a compression test on this engine, I have a tester with  a flexible hose but it only about 6" long, I would have to lengthen the hose to about 18" to screw it in the plughole and be able to fit the manifold.

I've this feeling you may be right about insulation breaking down Jane.

 

Supporting evidence woud be if it's worse on a hot engine and/or at high revs.

Yes sorry about slow progress..12 hour shifts dont help much!

Right today has had a little progress,

 

Spark is fine, tested the new and and the old just to make sure.

Did a compression test which brought up a problem, 180psi other cylinder number 1 which was 100psi

 

So we are left at the fuel..

Are you saying 3 cylinders are 180psi & one is down to 100psi? if so id squirt some engine oil down the plug hole & do another compression test on that cyl & if it comes back up to 180 ish then there may be a piston ring issue,if it still reads low maybe a burnt out valve? 

Yep put a little oil down and still came back at 100psi (and yes sorry my last post was not really that clear, 180psi on 3 and 100 on the 4th)

 

We dont think this is our problem, although it is an issue i dont think this is causing the misfire.

 

The strange thing was as it was running it was switching from 3 cylinders to 2 cylinders and back..this is screaming to me electrical 

I don't know much about the Renault engine or its set up. I was thinking would you be able to fit those spark testers that are made of transparent red plastic. If you can fit them you would be able to watch the sparking as the engine is running and see if any stop when you hear it starting to miss.

Yeah doesnt sound mechanical if its doing that,maybe have a look at the fuel injectors & their wiring & connectors etc.

I'm starting to agree with Jayne now, wiring/electrical problem.

One cylinder down on compression is not going to prevent ignition.

You did say no.4 and no.2 plugs were not firing earlier, is this still the case?

Another source of mis fires is the TDC sensor, that is located on top of the gearbox bellhousing where it meets the engine block, a wiring loom runs on top of it so it's not obvious that it's there. I've never had mine out but I do know they can be taken out easily and cleaned.  

It's getting to the point where you you are going to need help from Renualt Cup specialist but no one I know is up your way. Cliosport.net may be able to help, you should register there.

Yeah when we did the plug test it came back that two had a weaker spark but then just for the sake of it we swapped round plugs and found a better earth for them and they have a strong spark. So we ruled spark out.

 

We can smell unburnt fuel when its running so whatever it is doing by knocking off a cylinder then bring it back there is still fuel getting there. 

 

ATM im just at a loss so we are going to resistance test the wiring and test the injectors and go from there.

Most of the time i always have a hunch of what it could be but this time im left completely clueless 

I'm almost certain it's 2 separate things now based on the latest updates.

 

1) An electrical issue that's triggering a soft governer and shouldn't be.

2) A sticky or burnt valve (which may be caused or aggrivated by (1) ).

There waa even talk of a new engine :( but hopefully wont come to that

 

I do think its electrical mind

 

Completely forgot about a little test i used to love doing, getting a screw driver and using it as a stethoscope and listening for the ticking sounds of the injectors   

funny things these, we had a similar problem and it turned out cleaning the throttle body and the top dead centre sensor needed cleaning