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Clio 172 misfire under load

  clio 172
My 172 has bad misfire around 4000-5000 rpm. It only happens under load. You can drive the car around normally but then when you are at full throttle it judders really badly.

So far I have changed the coil pack, spark plugs, fuel injectors, fuel pump, lambda sensor. The engine was compression tested and came back fine.

Next I am going to change the intake gaskets, map sensor and iat sensor.

I'm now thinking its either the map sensor or vacuum leak after the map sensor. Could also be the head gasket but the oil looks ok and it doesn't seem to be losing coolant. I also plan to test the coolant for exhaust gases next time I'm working on the car.

Just wondering if anyone has any thoughts on what it might be. The car isnt road legal so its not easy for me to take it to a garage hence why I am trying to diagnose it myself before paying for a recovery truck.


Mr Trebus

Formerly known as Pot ltd Che
ClioSport Moderator
  Whichever has fuel
The money you have spent so far on parts darts, you could have just chucked someone £100 and got it taken to a garage to be diagnosed properly.
  clio 172
I haven't changed the leads but I did check them over and didn't have any obvious signs of damage. They were all carefully routed to avoid any snagging. I'm not shy about having a specialist look after the car, it has been over and back to the garage loads of times for major services like gearbox, diff, timing, air con delete, power steering delete etc. Just trying to fix this one myself if I can as the mechanic I use is a long haul from where the car is stored.