Running on 2 cylinders P0638

[R20BTG]

Currently at Donington. Car went into limp mode during Session 2. Check ignition warning, check ESP warning, spanner on dash. Limped back to the pits.

Running on Cyl 2 & 3, not running on 1&4.

Swapped coil pack on Cyl 1 for a brand new one, issue remains.

Removed all 4 plugs and look ok.

Fault code was P0638. Cleared code and issue remains with no fault code logged.

Any suggestions?

 

[turkie172]

Motorised throttle
valve automatic
control

 

[turkie172]

 

[turkie172]

 

[turkie172]

I don't know it might be the connectors to the ecu any way of checking spark or fuel delivery problem need diagrams let me know

 

[turkie172]

Reading around the coils are linked in pairs found articles with similar error message and problem will paste in here

Misfire on cylinders 1 and 4 Petrol 2ltr 16v*Fixed*​

Fixed

I'm pleased to say that thanks to a local garage - not a Renault dealer - the problem hs been resolved. The cause of the misfire on cylinders 1 and 4 was traced to an electrical failure of the injector on cylinder 4. I believe the multi-point injection system includes a feature whereby as each injector fires it triggers the corresponding coil(s) to generate the spark. Thus if the injector fails to fire then so do the coils for that pair of cylinders. If this is so then I would say that the diagnostic should know that the injector is not firing and to report it. Instead the blame is laid at the door of the coils that are not firing. If anyone has a good understanding of the fuel and spark system on these engines it would be great to have a posting as a point of reference. Does it exist? If not, is anyone out there able to give a simple overview that would aid troubleshooting. At the outset I asked my local Renault dealer to give me the definitive cause of the problem. He said it was definitely coils - but was wrong. I wasted over £150 due to that incompetence or laziness, and the car was off the road for several weeks. Still I now know where I can get good service here in the Charente.

Thanks to other Forum members for their help.

How Fixed

In my case the faulty injector was on cylinder 4 and it was "open circuit" electrically. The injector was replaced and all was well. I asked what had shown on the Diagnostic and was told that it showed as faulty injector and faulty coils. But the coils were not firing because of the injector fault. If your diag shows just coils as faulty then the injector would not be the problem - either the coil(s) - in which case replace all 4 plus spark plugs, or a wiring fault or an ECU fault would be most likely causes. If you take coils 1 and 4 and swap them with coils 2 and 3 and afterwards the problem has moved to the other cylinders it must be the coils that you moved that are faulty. If the problem stays on 1 and 4 then double check the cooresponding injectors ( 1 and 4) ae not showing up as faulty. If not then maybe a wiring fault or you may need to get the ECU sent away for diagnostic as a misfire on 2 cylinders is also a symtom of an ECU fault.

Good luck and let me know if you need anymore

 

[R20BTG]

That’s mega, thanks!

 

[R20BTG]

Looks like day over then, will need to take off the inlet manifold and investigate faulty injector. Thanks @turkie172

 

[turkie172]

I think the injector and coil loom connector is at the airbox side of the engine logic would say it's directly connected to the injectors and coils so testing at the connector would be as good as directly on the injector itself so no need to strip to gain access but if yours is a megalo I only have the loom diagrams for the Clio here but they might be the same.

 

[turkie172]

 

[turkie172]

 

[turkie172]

 

[turkie172]

So multimeter one probe in number 8 then the other probe to each injector in turn 7, 10 , 11 and 6 in ohms mode check the electrical resistance of each injector and look for any major difference.

 

[R20BTG]

Strangely I have this problem again, not quite as pronounced, but definitely running weak on Cyl 2 & 3. I do wonder whether there is a micro-break somewhere along the harness that serves 2 & 3 and I just got lucky replacing the throttle body.