Misfire

[Foxspeed]

as said the first lambda...spray round with brake cleaner see if the engine note changes if it does thats where your air leak is

 

[Jack Maxwell]

I've had a spray round with brake cleaner and found nothing. I've got a new upstream sensor on order.

What sort of readings would you expect from the sensor. I've got an OBD2 reader and been out driving whilst monitoring the voltage whilst monitoring O2 sensor 1 bank 1. If I go full throttle at any speed or i'm high up in the rev range the voltage will flatline at 0v

 

[Jack Maxwell]

Right is there any mapping gurus here.

Been out for a drive whilst checking readings. Under full throttle the O2 sensor is dropping to 0V so the short term fuel trim is leaping up to 99% to correct this. The problem is that the car is still running lean, if the fuel trim were to be dumping in fuel the car would be running rich?

 

[Dumdum]

It all depends if it’s running in closed loop or open loop, one pays attention to the o2 sensor (closed loop) and the other flat out ignores it and sticks to a predetermined map, if for some reason it’s stuck in open loop you need to find the cause (although I’d be tempted to say it would err on the side of caution and run rich)

Are your flexis ok? No blowing etc?

 

[Jack Maxwell]

I'm thinking it's just the lambda. I've attached a video of the readings i'm getting. You can see when i'm on throttle and the lambda is reading a voltage fluctuation the short term trim is moving about also but when i'm on throttle and the lambda flatlines at 0V the short term fuel trim is jumping all the way up to 99% and the lambda isn't detecting the richer mix.

 

[turkie172]

I would look at the physical evidence the plugs are white although I've seen white plugs in the 172 before that's lean the lambdas can sense and ask for whatever they want if the injectors are not providing enough fuel be it bad injectors or a dying fuel pump that cant provide enough fuel or pressure needed for the higher revs. Think about it your focusing on the symptom not the problem unlikely the Lambda works fine at low revs and not at high revs. The low fuel level misfire must be because of drop in fuel pressure be it the pump or the electric to the pump being cut off or a lower voltage than required causing under pressure. That's just an opinion I still could be totally wrong but better to say it, see if there is some way of watching fuel pressure maybe a corroded relay or connection might be the cause I don't know the layout but maybe a direct 12volt supply to the fuel pump would could quickly rule out the pumps power supply.

 

[Dumdum]

Can you swap the lambda with the second one if it’s the same plug or similar, often it’s just a plastic notch on the plug and the colour which is different, as far as I know the Clio doesn’t run wideband lambda

 

[Jack Maxwell]

Thats the issue finally solved. Looked like I was right with that Lambda reading 0v which was throwing the fuel trim right off. Fitted a new Lambda and all is good now, finally got some power smooth running again.

Here is a video of how the lambda should read: