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

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Mandrake
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by Mandrake »

Thanks addo, I just remembered I have a suitable blanking plug for the oxygen sensor hole that came with the back pressure testing kit, so I could take out the oxygen sensor and fit the blanking plug while the O2 sensor is sent away. The car will run fairly well without it, albeit a bit rich. (I ran it for over a month with it unplugged)

The hassle with that is it makes swapping the sensor into two separate jobs which wouldn't matter if I was doing it at home but when I'll have to go visiting ( ;) ) to get it done its a duplication of effort...

My MOT is next Monday so I'll have to leave it until after then as it will probably fail the lambda test with no oxygen sensor fitted. I'll just have to cross my fingers that it works on the day, (it still works intermittently, but seems to have a long warm up period) and if it doesn't I'll have to replace it before the retest...

If I'd found out about it a few weeks ago I could have dealt with it before the test but its too late now.

RichardW
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by RichardW »

I might be on holiday though.... :wink: :lol:

citronut
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by citronut »

trouble is these days everything you can imagine and stuff you cant is being faked,

only the other day on the box they were showing air bags that were fake exploding instead of inflating, then followed by lots of shrapnel,

i purchased a Bosch boxed Lambda sensor from E*C*P a while back fitted it took the car for its re/test, failed on the Lambda,

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Mandrake
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by Mandrake »

citronut wrote:trouble is these days everything you can imagine and stuff you cant is being faked,

only the other day on the box they were showing air bags that were fake exploding instead of inflating, then followed by lots of shrapnel,

i purchased a Bosch boxed Lambda sensor from E*C*P a while back fitted it took the car for its re/test, failed on the Lambda,
Counterfeiting of parts is certainly something to consider - how much counterfeiting goes on in the car parts industry ? Of course pattern parts are by definition copies of original types, but how many parts sold as OEM are really disguised pattern parts ? And how many well known name brand pattern parts are actually some other lower quality pattern part not the one claimed ?

Counterfeiting is a major problem in electronics components for the last 20 years or so, its got so bad that certain types of transistors if you order them over the internet from anyone but a major big name supplier you're very likely to get counterfeits and never know it unless you cut them open or destructively test them.

Often the end seller is not even aware that what they're selling is counterfeit as they have been duped further up the supply chain. (There have even been multiple cases of big name respectable retail components suppliers accidentally selling counterfeit transistors, let alone mum and pop outfits)

Only by tracing the supply chain right back to the source can you be certain...

larppaxyz
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by larppaxyz »

Hi, me again :)

I today took apart most of the electric harness, checked all connectors and wiring. I added some extra insulation for spark plugs (they go very close to sensor wiring) and also added one extra earth cable from engine to chassis.

Let's see how long it works this time.

I did this because me issues are getting worse. Now there is stalling while driving on highway and sometimes when idling. Om highway, it just stalls, and when you move your throttle a bit, it comes to life again. Sometimes it just skips a beat once or twice.

Yes.. it could be engine speed sensor, it really could... i had similar failure with my BMW.

I thing it's time to start looking for a new car... my MOT is in few weeks too :)

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Mandrake
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by Mandrake »

RichardW wrote:I might be on holiday though.... :wink: :lol:
Holiday ???! All holidays are hereby cancelled until the end of the year :mrgreen: :lol:

Seriously though, I'm just going to put it through the MOT on Monday and see what happens. If it passes the emissions test the oxygen sensor can be done "at leisure". The car will run fine without it for a few weeks, its just the emissions test that will probably fail on the lambda reading without it...

The symptoms it has do seem a bit like a faulty heater circuit causing it to rely on exhaust gases to heat up (I remember saying to you when we first fitted it that it seemed to be a lot slower to warm up than the original) so I thought I better investigate that.

I checked the wiring diagram tonight and not surprisingly unlike more modern ECU systems that measure heater current and report a fault if the current is out of spec, there is no monitoring at all. #-o The power comes through one of the maxi fuses, through the double injection relay, through another fuse and then straight to the oxygen sensor with no monitoring. So even if the heater was open circuit the ECU wouldn't log a fault. :roll:

The only testing it really does is that if the sensor doesn't "wake up" and start working within a certain amount of time (a few minutes it seems) then it logs an intermittent oxygen sensor open circuit fault, so it can only deduce a heater fault through the sensor taking too long to become active, which of course probably would only trigger if you started the car and let it idle in cold conditions, if you drove off quickly the exhaust heat would get it up to temperature quick enough to avoid setting a fault.

Anyway I haven't measured the resistance before so I checked it tonight and the heater resistance is 6 ohms, which is pretty much what it should be so its not a faulty heater unless there's an intermittent break in the wire.

I plugged it back in and went for a quick drive with the Lexia - the oxygen sensor was working perfectly during that test drive. :roll: Fingers crossed it does on Monday too!

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Mandrake
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by Mandrake »

I was browsing the internet today looking for clues for the intermittent performance/misfire issue, (as you do :lol: ) and came across this old Aussiefrogs thread:

http://www.aussiefrogs.com/forum/peugeo ... sfire.html" onclick="window.open(this.href);return false;

There's quite a bit of misinformed speculation mixed in with the discussion ("try swapping over two of the coil packs", yeah, like you can do that on an ES9J4 with a moulded 3 coil pack :twisted: ) but here are a few interesting bits snipped out.

The original poster, after just filling up with petrol:
68 404 wrote:After about 40 kms it started missing, especially just off idle. It felt like it was running oin 5 cylinders or something. There is still some sort of hesitation and there is a definite miss at idle every 5 secs or so.
pokinacha wrote:Mines does something very similar.

when warm, above 90C, it will missfire randomly up to 4000rpm. mainly around 2000-3000 but somtimes lower. I've never had it at idle, and above 4000rpm it seems fine. mine has a better flow exhaust so i can hear the missfiring better. sounds like overrun crackle.

i have been told it's a coil issue. just haven't done anything about it yet.
These symptoms of pokinacha's sound very similar to what I had for a long time - no misfire at idle, running perfectly above about 3500-4000 but hesitation and lack of performance below 3500. It's now misfiring at idle as well, like the original poster in that thread. I also notice that power "jumps" suddenly up at 3500 rpm when accelerating... Continuing:
68 404 wrote:It's getting worse!

No problem when cold, it seems to manifest itself when the underbonnet temperature gets hot.

The miss is very present at idle and when throttle is initially applied (like accelerating away from lights). There is an obvious multiple miss under these conditions and then it might clear its throat and accelerate away.
68 404 wrote:Car had full service about 10,000 kms ago (plugs were changed).
And finally the resolution:
68 404 wrote:The 406 is back!

It was the crankcase breather that was the problem. It was full of gunk, perished to a large degree, and totally blocked. The blow by from the engine caused oil to pass beyond the gasket of the crankcase vent, run down towards the plugs causing the misfire!

The coil pack was cracked but is still serviceable. Despite his best efforts, my mechanic couldn't find anyone who would supply a non genuine coil pack...
So can anyone tell me whether the crankcase breather scenario is plausible or not, (or whether his mechanic was spinning him a line) and if so exactly which pipe is being referred to, as there are multiple breather pipes running about the engine...

One thing that does agree with the above scenario is that when I changed the spark plugs a few months ago (detailed earlier in this thread) the front bank were ok but the rear bank plugs were badly fouled to the point that the plugs were causing a misfire even though they were new plugs just a couple of thousand miles and a few months before they came out fouled.

According to someone earlier in the thread (xantia_v6 ? sorry I can't remember) the crankcase breather fumes that go into the bottom of the throttle body are directed to only the rear cylinders not the front...

Again I doubt this is all the issue with this car otherwise the performance would have been normal when I recently changed the plugs - at least for a while, and while there was a big improvement it still wasn't running right, however its possible that those rear plugs are beginning to foul again now, if so I need to find why.

Just a thought... :)

Hell Razor5543
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by Hell Razor5543 »

It is plausible. A friend had his bike cut out at random intervals. Turned out the fuel tank breather hole was blocked, and as it was a gravity feed, the engine got starved. Blowing through the hole cleared it, and resolved the problem.

Stempy
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by Stempy »

Mandrake wrote:
According to someone earlier in the thread (xantia_v6 ? sorry I can't remember) the crankcase breather fumes that go into the bottom of the throttle body are directed to only the rear cylinders not the front...
It may have been me. When I had the inlet manifold off I noticed that the rear bank had oil staining whereas the front bank were clean and shiny. I investigated as to why this might be and the conclusion I came to was that if you look at where the crankcase breather enters rubber inlet hose it is directly inline with the left hand split of the manifold which feeds the rear three cylinders. Had I kept the old girl I was intending to blank off the breather entry to the inlet hose and allow the crankcase to breath directly to atmosphere via a filter and possibly a catch tank. :rock:

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CitroJim
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by CitroJim »

It's plausible. The breather is in three parts. There's a one-way valve mounted in the valley of the vee just by the knock sensor and two pipes leading off from the camboxes. All three join up and go into the throttle body. Often the pipes get brittle and crack in the heat and thus cause false air to be sucked into the throttle body.

It's possible for the one-way valve to block I suppose but once again it's a pain to get to - being under the inlet manifold...

I'd think it would be more like as Stempy says, for a break to occur in the pipework and I concur that Stempy's idea of blanking off trhe throttle body port and running the breathers into a catch tank is a good test... You can get a nice polished ally one...

Recall that I dealt with a car suffering almost exactly as the Ausiefrogs one did and that was fairly and squarely the coil. Have you got your name against the one on Will's scrapper Simon?

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Mandrake
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by Mandrake »

Now that I read the Aussiefrogs post again I'm not sure it is the same thing I noticed - is he saying that the breather pipe was blocked causing oil to be forced out past the breather pipe o-ring into the spark plug wells and fouling the spark plug that way ?

If so that's not what's happened to mine as I've never had oil fouling the spark plugs on the top side of the plugs, in my case the insulator tips on the electrode end of the spark plug of the rear plugs were carbon fouling far more than the front ones, possibly from excess ingested oil vapour through the inlet manifold, so not the same thing.

Yes Jim, I have my name on the coil-pack from Wills breaker as well as the fuel pump. I'm not happy at all with the original coil pack which is now back in the car. Even at idle there is about a once a second misfire most of the time. The new one I had in for a few months that broke down was from a clearance house who aren't responding to my queries regarding refund/replacement so I guess I'm stuck with a lemon there, hence nabbing the one from Will...

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Mandrake
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by Mandrake »

Another possibility that I'm investigating in relation to false knock sensor retard is replacement of the ignition suppression capacitor mounted above the coil pack:

Image

Image

I still suspect false knock retard to be the cause of the sudden increase in power above 3500 rpm (or rather the sudden loss of power below exactly 3500 rpm) and it occurs to me if this suppression capacitor has failed there could be a lot more ignition coil hash in the B+ to the ECU than there should be, possibly being picked up at the knock sensor input, as the sensitivity of the knock signal input is in the tens of millivolts range.

I haven't tested the capacitor nor have I tried to replace it, and I haven't put my scope on the B+ line at the capacitor to check for hash either.

The interesting thing is that the capacitor is not shown at all on any of the wiring diagrams that I have - they don't even acknowledge a 5th wire on the connector! This makes me think that the capacitor was added rather late in the design/testing process possibly as a band aid after some problems with interference were noticed - many but by no means all coil pack based cars seem to have this suppression capacitor on the coil B+ line from what I can see.

It's a few quid to replace it so it won't hurt to rule it out. :) (although finding one that's physically the right shape, value and has a high temperature rating is proving challenging, it seems to be rated at 100 volts and 100 degrees C from what little I can dig up on it, and clearly says 2.2uF on the side)

As I've said before, I think I have at least two distinct problems at the moment, one being a coil-pack related misfire, but there is something else going on as well.

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CitroJim
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by CitroJim »

I'd not use that new capacitor Simon. Obviously a fake as the mu is backwards... Take a closer look!

My S1 ES9J4 Injection diagram shows the capacitor hanging off pin 4 of the coil but bizarrely the S2 one doesn't :?

It's on the supply side to the coil so it'll work absolutely fine without it I'm sure...

I've never heard of one going and to be honest and many I've seen look a bit rough around the edges..

Still, no harm in swapping it...

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Mandrake
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by Mandrake »

CitroJim wrote:I'd not use that new capacitor Simon. Obviously a fake as the mu is backwards... Take a closer look!
That's the original capacitor Jim! :lol: With a date code of '98 and a moulded wire...I haven't sourced a replacement yet. Can't say I noticed the mu symbol was back to front though. :mrgreen:
My S1 ES9J4 Injection diagram shows the capacitor hanging off pin 4 of the coil but bizarrely the S2 one doesn't :?
Weird! Wonder why they left it off the diagram on the S2.
It's on the supply side to the coil so it'll work absolutely fine without it I'm sure...
I've tried disconnecting it before and it made no difference, that could either mean it's not essential, or that it's already faulty! The engine will still run without it sure, its not like a points capacitor, but you have 10 amp spikes drawn by the coils with very steep turn off times, so there's quite a potential for switching hash to get into the main supply line. You would think that they wouldn't bother to fit it if there wasn't a good reason...if they could save a few pence leaving it out they would.
I've never heard of one going and to be honest and many I've seen look a bit rough around the edges..

Still, no harm in swapping it...
Indeed, as long as I can find a suitable replacement - temperature rating is my main concern since its in such a hostile location bolted to the top of the cambox cover. I'd be kicking myself if I didn't rule it out and much later found it was the cause of one of the problems! #-o
Last edited by Mandrake on 26 Jul 2013, 20:30, edited 2 times in total.

Stempy
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by Stempy »

As far as oil on the top side of the plugs is concerned I can tell you that it didn't at all affect the running of my Xantia when I inadvertently left the oil filler cap off and filled the front plug tunnels with oil. :oops: I only realised my dickheadedness when I stopped and smelt the hot oil :shock: I continued the rest of my journey with no ill effects (having refitted the cap and topped up the oil). :shock:

This any good?

http://cpc.farnell.com/ampohm-wound-pro ... dp/CA06110" onclick="window.open(this.href);return false;