Xantia V6 broken exhaust (update: and rough low rpm running)

[isisalar]

Hi Simon
Reading through your last couple of posts mentioning the air temperature sensor attached to the filter box, and how things change when it's not giving any input, could it be worth changing it?
The outside temperature gauge on my old VSX, when it had gone wrong, would often read 30 degrees or so out, so lots of potential for a faulty sensor to affect things if it's giving false information to the ECU I would think.
Cheers
Paul

[larppaxyz]

Interesting! What is the issue with the 406 air sock that you're referring to ?

Sock easily get crushed when doing other maintenance on car and it's not easy to see if it's crushed unless you take it out. It looks like this

http://performancepeugeot.com/shop/imag ... 20Pipe.jpg" onclick="window.open(this.href);return false;

On 406, you can simply pull it out, but after that airbox sucks air close to radiator, so it's bit hotter. I have my sock "hanging there", so some air is still coming through sock.

Air intake temperature sensor is connected to airbox on my car, right before ICV hose. It's possible to pull it out (i replaced it long time ago) and leave it hanging there so i doesn't give any errors to ECU.

I did quite a few trips today, and car still feels pretty good. It really accelerates well. Still good...

[Stempy]

I replaced my 'sock' with a length of flexible drain hose. The PVC type with a spiral wire former. You can route it the same as the 'sock' so you get a good cold air feed.

[Hell Razor5543]

If you could get hold of one, I wonder if a plumber snake could help? Failing that, pop the filter out, and give the sock a shot of compressed air.

[addo]

The factory ducting is breathable; that's part of how it mitigates risk of hoovering up a lungful of water.

[myglaren]

The factory ducting is breathable; that's part of how it mitigates risk of hoovering up a lungful of water.

Didn't stop mine from drinking from the gutter

[larppaxyz]

I did a quick Dremel job with my old TPS

http://uli.ulicode.fi/406_tps.jpg" onclick="window.open(this.href);return false;

I took photo with my mobile phone (and scaled it down) so there is not much details to see, but i can assure it was time to replace it. Good cleanup could still give it few years... maybe.

My car is still running very very nicely after latest repair job.

[Mandrake]

Reading through your last couple of posts mentioning the air temperature sensor attached to the filter box, and how things change when it's not giving any input, could it be worth changing it?
The outside temperature gauge on my old VSX, when it had gone wrong, would often read 30 degrees or so out, so lots of potential for a faulty sensor to affect things if it's giving false information to the ECU I would think.

I think you misunderstand - while the stumble when snapping the throttle from idle didn't seem to be there (during a brief test) with the air box off and air temp sensor disconnected, overall performance is a lot lower especially anything beyond about half throttle doesn't seem to give any extra oomph. As I say I'm not sure whether that's the lack of the air temp sensor or whether it mucks up the inlet tuning.

The air temp sensor SEEMS to be working according to the Lexia - on a dead cold engine first thing in the morning the coolant temp sensor, air intake temp sensor and outside air (dashboard) temp sensor all agree with the prevailing weather conditions within one or two degrees...

What I do notice is that when the engine bay is hot the air intake temperature reading is a lot higher than ambient - around 30 degrees or more higher. For example yesterday it was reading 30 degrees for the air intake temperature (with a fully warmed up engine) when outside it was 2 degrees... and in the summer I've seen readings as high as 45 degrees for air intake temperature when its 16 degrees outside...

I assume that the hot engine bay and air ducting / filter box is able to warm the air as it comes in and that the reading is valid, can anyone confirm that their intake air temp reading on the Lexia is 20-30 degrees above ambient with a hot engine ?

[Mandrake]

Interesting! What is the issue with the 406 air sock that you're referring to ?

Sock easily get crushed when doing other maintenance on car and it's not easy to see if it's crushed unless you take it out. It looks like this

http://performancepeugeot.com/shop/imag ... 20Pipe.jpg" onclick="window.open(this.href);return false;

See that's exactly what my concern was, that the sock could get crushed and restrict air flow without necessarily being able to see anything wrong with it.

Can anyone tell me how it attaches at the grill and whether its possible to remove it and refit it without removing the grill ?

Air intake temperature sensor is connected to airbox on my car, right before ICV hose. It's possible to pull it out (i replaced it long time ago) and leave it hanging there so i doesn't give any errors to ECU.

That's a good idea, I'll see if I can pop the air temp sensor off the box so I can leave it connected when doing the throttle snap tests with the air filter box off. Of course it won't read quite right when its not in the intake air stream but it will be better than an invalid reading from being disconnected.

By the way I think I've just realised why the ICV opens fully when the throttle is open and the car is accelerating - so that sufficient air flow passes the air temp sensor which is located in the feed to the ICV. If it did not open then most of the air flow would bypass the temp sensor when the throttle was open and possibly lead to a false or slow responding reading.

[Mandrake]

The factory ducting is breathable; that's part of how it mitigates risk of hoovering up a lungful of water.

Good point!

I was liking Stempy's idea of replacing it with wire reinforced flexible PVC ducting but as you point out the original is porous to water, allowing any water splashes to drain through the fibres. If it was replaced with something water tight water could pool at the bottom of the U shaped bend below the filter box leading to a gulp of water being ingested. Unlikely perhaps, but potentially devastating...

[Mandrake]

I did a quick Dremel job with my old TPS

http://uli.ulicode.fi/406_tps.jpg" onclick="window.open(this.href);return false;

I took photo with my mobile phone (and scaled it down) so there is not much details to see, but i can assure it was time to replace it. Good cleanup could still give it few years... maybe.

I can't really tell from the picture what you're suggesting is wrong with it - are you referring to the wear on the carbon track ?

My car is still running very very nicely after latest repair job.

Glad to hear it, fingers crossed it stays that way!

So far mine is running very nicely too. Today was the first time that I've had a chance to drive it any distance since the work done on it last Sunday, and its going like a bat out of hell.

What's interesting is today is very cold (around 2 degrees when I was out in the car) but is also very wet - previously the performance was considerably down in damp/wet conditions with a noticeable under load misfire - today the performance is perfect even in the damp wet conditions.

This suggests my theory of HT leakage on the ignition leads somewhere may have had some merit, even though I couldn't see anything visibly wrong with the leads I took out. (I've kept them so I could potentially do some bench testing on them with one of my spare coil packs)

I also took the plugs out to inspect them - same as last time they were perfect, a little bit of carbon around the edge near the thread but the insulator was bright white and perfectly clean with the electrodes looking perfect as well. I refitted and torqued them with a torque wrench this time to 26 Nm. (Last time they were fitted new with finger tight + 90 degrees, but I can't do that once the washers are already crushed)

Whilst the TPS doesn't seem to have done anything for the stumble/hesitation when flicking the throttle from idle, the performance has been absolutely consistent over the last week with no inexplicable periods of "flat" performance and poor throttle response. Bear in mind the substitute ECU is still fitted - tomorrow if the weather is ok I'll be trying my ECU again to see if there is any loss in performance.

I like your theory (that I also had) that an intermittent TPS signal was causing intermittent false recalibration of the TPS input of the ECU... a false recalibration that would cause flat performance and poor throttle response until the ECU was reset.

I'm still a bit puzzled about the cause of the stumble just off idle - another thought other than restricted air intake that has just occurred to me is what if someone has played with the idle limit screw on the throttle body in an attempt to fix the surging idle issue ? Normally the idle screw on an ECU controlled ICV system should not be touched, but problems with idle regulation can occur if it has been tampered with.

Unfortunately there is no documentation on where it should be set, since you're not supposed to touch it...

[Stempy]

The factory ducting is breathable; that's part of how it mitigates risk of hoovering up a lungful of water.

Good point!

I was liking Stempy's idea of replacing it with wire reinforced flexible PVC ducting but as you point out the original is porous to water, allowing any water splashes to drain through the fibres. If it was replaced with something water tight water could pool at the bottom of the U shaped bend below the filter box leading to a gulp of water being ingested. Unlikely perhaps, but potentially devastating...

Never once had any problem with water ingress in many thousands of miles. If you were worried you could always cut a small drain hole at the lowest point.

[myglaren]

I wanted to shove some of those plastic pan scrubber things in the hose to reduce the possibility of water being sucked up but haven't found any yet.

In the airbox is a sort of descending 'horn' beside the inlet pipe. Mine was full of water and grit and the air filter soaked. The MAF was also corroded badly, which is why it failed, presumably.

[citronut]

like these Stevey baby

http://www.3m.com/product/information/H ... -Pads.html" onclick="window.open(this.href);return false;

or

http://www.ebay.co.uk/bhp/scouring-pads" onclick="window.open(this.href);return false;

[Mandrake]

Would something like that not restrict the air flow though ? Without necessarily making a significant difference to the risk of water ingestion ? They are porous to water after all...