Renault Clio III 2007 1.6L 16V no O2 sensor signal

that was not good ! We just wanted a presure test to confirm or discount the cats

Let's start from scratch I'm sure I can help you solve this ,if I give you some checks if you do just them and get straight back to me ,there's a few things I need

1) since you've deleted the codes does your front and rear o/2 both end up pegged at 0 ?
2) your front and rear o/2 did not agree so we need to know which one is reading correct that's so important .if the front stays negative and the rear is high give it a good squirt of car clean while watch the front and rear o/2 and see if you can capture for me in the screen shot the result
3)I need to know how long a time your screen runs for on your screen shots ,so you have 10 numbers along the bottom can you adjust the time and if not time with a watch how long it takes for it to move from 1to 9 (10 is out of view) and from now put all info in graph view
4) when you run it and your problem is there back probe the signal wire of the rear 0/2 and short it to ground so we can see if the fuel trims are being forced into negative becouse of the rear o/2 signal

If you can do these we can move forward ,we haven't run out of things to check but you need the answers to these questions and be able to be sure of the results to move on ,becouse you could have more than 1 problem here but we need to know which o/2 to trust ,don't give up your not that far from beating this

Thanks for the support Chris!

I can only answer the first one right now: o2s doesn't seem to get pegged at 0 anymore, except for the moments where the CEL blinks, which has happened twice since the first memory wipe with the good scan tool.

And if it's useful, I've confirmed PCM is activating heaters on both sensors successfully.

Will do the rest and report back.

Ok good I have a few other things depending on your results

Random update:

Went to tech's shop. Performed two tests aimed at rule-out head gasket issues or compression issues.

1. Pressure test on coolant system: Added 15psi, left for about 10 minutes. Pressure dropped to about 7 psi, revealing a small fissure on the thermostat housing. Apparently no signs of coolant leaking into the combustion chamber. Valid test?

2. Compression test: not sure if this was a well performed test, but all 4 cylinders were in between 128psi - 145psi. I haven't found the spec for this engine. Still looking. Is that OK for compression?

www.dropbox.com/s/af04srohnztvxbr/File_000.mov?dl=0 -- a 5 times "crank" read reading about 135psi.

www.dropbox.com/s/1xal5jvaqlpio5o/File_001.mov?dl=0 -- not sure about this one and that "pop". he repeated the measuring on this same cylinder, read about 128psi (could record that take).

Can this by any change be related to the rear O2 reading issue?

Will try to do the other tests tonight and report back.

Your compression readings are good not excellent but they are the same as mine if not slightly better so no issue there ,couldn't really hear the pop sound very well on video but nothing is related to your 0/2

Report on tests requested:

1) No O2s pegged either way. They respond to events (not sure about the accuracy though).

2) Carb clean added seems to create a rich response in both O2s: www.dropbox.com/s/xiusn4f7bxcpn82/carb%20clean%20added.png?dl=0

3) Time the scan tool graphs per each pass: 12 seconds.

4) Here's a snap of what occurs when rear O2 is grounded.

Before: www.dropbox.com/s/ljytgj2fw3je849/before...0downstream.png?dl=0
After: www.dropbox.com/s/f9pxzzwz59f53sg/after%...ream%202min.png?dl=0

Will post some additional findings in another post.

Additional info 1/2:
When trying to add carb clean, I expected a lean response in both O2s as soon as I disconnected the hose. Instead, I noticed like the car was able to breath better (no hissing on the hose disconnected). Revs and Intake PSI seemed to be more consistent with the hose off. That made me question the air filter condition, so I opened the box, took filter out, and, although it seems to be OK, the fit seems to be too tight once I try to close the box. Can that be restricting air intake?

Intake hose just disconnected: www.dropbox.com/s/mb1ewke9ghu9bi7/vac%20...take%20hose.png?dl=0

Intake hose left disconnected for about 1 min: www.dropbox.com/s/8vmm83phs210hx9/hose%20disconnected.png?dl=0

I did a test drive without air filter (bad idea?) and noticed a better idle regulation, slightly better response with throttle open, but at high revs feels sluggish and the occasional hesitation.

Additional info 2/2:

Noticed that at higher revs sustained for more than 20 seconds, downstream signal slowly decreases, but when back at idle, signal climbs up again (slowly) upwards to around 750mv - 800mv:

www.dropbox.com/s/ht8evgqxl7lfyju/hi%20r...%20reaction.png?dl=0 -- If revs are sustained for longer, rear O2 voltage keeps decreasing down to about 600mv.

Air filter state and the hose I've been using to add carb clean / inducing vacuum leak:

Just looking through all the info at the moment so much better thanks just a quick question will reply on rest when I get home but this hose looks like a crank case breather hose? And that's before the throttle body ? Sorry can't see the hole Inlet , did the hose have suction and did you spray in small hose or the big inlet ?

I did spray in the small hose. To be honest I'm not sure what is that hose for, it has very little suction, and goes from the air intake hose (the one that connects air filter box to throttle body) to the back of the intake manifold (plenum?).

That's the hose I've found that bypassed the throttle body due to my (absurd?) fear of spraying carb clean through the throttle.

Let me know if i should find a different entry way for carb clean. Maybe through the air filter box? Throttle body hose is almost impossible to disconnect without removing the air filter box anyway.

Thanks for your patience Chris.

Couple of quick questions
When you said in one section you left the hose disconected for a little while was this the small hose?

Yup, that was that small hose...

When you added carb clean to the engine this time they both reacted which is great , but just before about frame 10and 9 it appears it was running perfect ? Can you remember when you done this test what had you done was the car just started or run for a bit or had you done anything ?

Car was warm already from a previous drive (for about 10 minutes).

For what I remember, frames 10-9 are of car idling with the hose disconnected (so I could add carb clean).

I haven't left work yet and got a 2 hour trip home will look over the stuff then but if you can unplug the small hose and run the car so it's hot when you have the issues and see what the trims are like and let me know , also when did it last have an oil change and does it use oil or is does the oil level ever apear high ?

Oh and give it a quick run with this pipe off and see how it drives , I can pick up your posts but it won't let me reply when using 4 g mobile signal on way home thanks chris

Not sure about oil level because stick broke at the graduated tip and I only monitor the indicator at the dash.

Don't think it's low but it might be high. No idea how can I verify this without a stick.

Last oil change was about 1200km ago.

I also have issues replying while at 4G

If i understand correctly about your request is:

Start car and let it warm with hose disconnected.
Drive with hose disconnected and monitor fuel trims.

Is that correct?

Yeap