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

[Mandrake]

Didn't that 605 owner tear down the motor in some rapid timescale? From memory he was pretty casual in his writeup but didn't faff about in the work.

I think the V6 knock sensor is largely where it is, for reasons of practicality - outside the block it would be perilously close to exhaust heat. Failures across the internet seem very uncommon.

It's the best/only place for it to be really, just damn inaccessible.

Failures of the ES9J4 knock sensor on the internet might be rare (I haven't found a single confirmed case) but that's probably because failures of the ES9J4 in general are almost impossible to find on the internet either. Apart from the usual suspects like oil in the spark plug wells, coil packs, coolant temp sensors, timing belt, that sort of stuff they really do seem to be almost bullet proof. Any time I look for faults for the ES9J4 on the internet to pursue a certain theory I almost always turn up nothing, not even any google hits, and can't find anyone else reporting the same thing. There's just so few people complaining about them. I have come across the occasional reference to intermittent poor low rpm performance identical to mine but nobody experiencing it seems to have identified the cause or fixed it. If I do finally nail this problem I may be blazing the trail for others...

[Stempy]

I'm going to try the flushing agent and the additive to see what happens. If that does nothing then I might admit defeat...

Or you could just buy this one

http://www.ebay.co.uk/itm/221248537552? ... 1423.l2649" onclick="window.open(this.href);return false;

But I've gone off Series one styling now after a year of Series 2 ownership... I'd forgotten how different the dash instruments are too...and the front is just too blunt looking... I also don't like silver so if I replaced this one I wouldn't be wanting another one in silver...

Seriously though, 71K is nice, but... London...couldn't really be any further away. No where (literally) for me to put it even if I could get it back home, nowhere to work on it to do the inevitable work that needs doing etc...

While we're staying with the inlaws buying another car is a non starter unless this one outright spits the dummy and dies on us. Lets face it, I'm unhappy that it isn't performing as well as it should be but it drives us from A to B and touch wood, aside from the broken exhaust (that could affect any old car) and the minor banjo leak it hasn't really let me down in a "can't drive it" way yet, despite all of the niggles I have. As far as my other half is concerned the car works fine so she doesn't understand why I'm always tinkering with it... Selling an apparently (to her) working car and buying a fresh load of trouble would not go down well when we're saving for a house.

When we get settled into our own house again with hopefully a garage or at the very least a drive way, then I may go on a fishing expedition to see what other V6's in better condition are available, but not just now. With a bit of luck by then David will have completed his V6 Activa conversion and already got bored with it...

But for that price you could use it as a donor, complete engine and gearbox swap then sell the rest to metal mickey....

[addo]

The Alfa is running a bit raggedy at present, too. Just noticed tonight.

Are you going to stimulate the ECU with a fake knock now, to see if it does the same thing? That should be cheaper/easier than undoing bits of the motor.

[Mandrake]

But for that price you could use it as a donor, complete engine and gearbox swap then sell the rest to metal mickey....

But doing so would require (a) somewhere to park a second car, and (b) somewhere and somehow to swap an engine and gearbox. I have neither of these, as I keep trying to point out to everyone.

If I had the time, space and equipment to lift an engine and gearbox out at my leisure I'd be overhauling the existing gearbox to end up with a known good one, not throwing in a replacement of unknown condition that could potentially fail even sooner than the one already in there..

[Mandrake]

The Alfa is running a bit raggedy at present, too. Just noticed tonight.

What sort of raggedy ?

Blocked cat surely ?

Are you going to stimulate the ECU with a fake knock now, to see if it does the same thing? That should be cheaper/easier than undoing bits of the motor.

Don't worry, changing the knock sensor would be a last resort only if I conclusively proved it to be at fault, and I wouldn't do it on the side of the road either. (Thus it would have to wait until we move again) I'm just happy that it looks like a fairly do-able job should it be needed, not something out of my reach. Not particularly expensive either, a fraction of the normal cost of a coil pack for example, in fact well under the price of a tank of petrol...

I wasn't planning to try to simulate fake knock, one problem with that is the ECU will only be listening over a narrow range of frequencies around 6Khz, and only at the time intervals in the combustion cycles when detonation could occur so I can't feed any old garbage into it, it would need to be a fairly specialised signal which I don't have equipment to produce.

The other problem is I'm not sure what it would prove - yeah, the performance would drop but how could I prove that it dropped for the same reason as it has been dropping by itself ?

My approach is the opposite - try to desensitise the knock sensor a bit so there is still enough activity that the ECU doesn't think the sensor is dead and go into failover mode, but not enough that mechanical (non pinging) noise is triggering it. I don't know for certain whether the knock sensor in the ES9J4 is a narrowband (mechanically) resonant one or a broadband one with bandpass filtering in the ECU, so that will affect the best course of action. Potentially a single carefully chosen resistor in parallel with the two signal wires may be all that's needed.

I have a roll of high quality shielded twisted pair mic cable with foil and braid screen that is probably as good quality as the knock sensor cable (although not high temperature) that I could tap in parallel with the knock sensor at the engine ECU connector and bring into the cabin in the same way that I did with my Hydractive LED. That would let me connect a scope to it inside the car and/or switch various resistors in parallel with the signal wires. Something like a small switch box with 3-4 positions on it. I should have the bits I need for that somewhere here...

I don't know for sure whether the extra cable would pick up too much noise but if I run it from the ECU along the right wing and in through the drivers door shut (the same path I used for the Hydractive monitor LED) it should be reasonably away from engine interference. At worst interference will just cause even more knock retard than I'm getting now!

[Mandrake]

Well after all the discussion about suction pumps I used a very low tech way to drain the oil, mess free as well.

I had a 60mL syringe handy which I thought would do the job on the end of a rubber hose without buying anything fancy but before I even tried that I just shoved the hose into the dipstick tube and tried syphoning it:




Who needs pumps when you have gravity! Not exactly fast, a few minutes to syphon 1 litre, probably not suitable to drain the sump for an oil change but sufficient to drop the level down a bit.

I put the Lubegard in, left the ECU connector off for a few minutes and went for a quick drive. As always seems to happen when the ECU is reset the engine was very responsive and zippy for the first few minutes but lost a little bit of zip at lower rpm after a while. Performance at higher RPM was good throughout. When I got back I listened to the tappets and they're not noticeably quieter yet, mind you the wynns additive didn't make an audible difference for a day or two either, so I don't expect instant results.

What I did notice however is that the overall engine noise (not tappets) as heard while driving the car seems quite markedly quieter and smoother than before particularly when revving the engine hard. Maybe its wishful thinking but I don't think so. It sounds more like its purring now and not as raspy as before.

The car hasn't been driven since Saturday and both engine and gearbox were feeling nice and smooth.

By the way the oil I drained out was completely black despite being changed only a month or so ago... does that suggest that I should do my next oil change a bit sooner than normal ?

[addo]

That won't hurt. Black oil can be a result of blow-by as well.

[Mandrake]

Past the rings you mean ? How does that tally with good (210 psi dry) compressions ?

[CitroJim]

Simon, I am still reading even if not contributing... Reading with interest as always

That oil looks remarkably black for some that's been in there for a very short while...

You need to do what yo did with the gearbox and give it several frequent changes. On both mine they hold their oil colour for a very long time...

[Mandrake]

I agree Jim, I was quite disapointed to find the oil is basically completely black, same colour as the last lot was, and its only been a few hundred miles and a month or so since I changed it.

I don't think the maintenance of this car especially fluid changes has been kept up before I got it...

I'll do an early change of the oil (and filter ?) but it won't be for at least a couple of months. (I don't do a high mileage so it will have only done a few hundred miles by then)

[larppaxyz]

I can't see why it wouldn't work, it might require an L-pad (series and shunt resistors) or depending on the impedance of the piezo and how the ECU detects a faulty sensor the right value of shunt resistor in parallel may be all that's required, avoiding cutting any wires. I won't know until I try.

I'm going to try the Lubegard first though.

Could you simply get second hand knock sensor from somewhere and connect it electrically, but leave mechanically disconnected?

[Mandrake]

Could you simply get second hand knock sensor from somewhere and connect it electrically, but leave mechanically disconnected?

No I don't think this would work, because the ECU expects to hear a small amount of engine noise from the knock sensor any time the engine is running even when not pinging/detonating.

If this "background" noise is not detected and the knock sensor is completely silent the ECU logs a fault and goes into a fall back mode where it permanently retards the timing map.

Besides, even if it did fool it it would be dangerous to run an engine with such a high compression ratio with full timing and no working knock sensor, especially if there is a possibility that there is real knocking due to a lean running fault.

[Mandrake]

Well, once again I am impressed by a Lubegard product

I only put the stuff in yesterday, when I started the car today the tappets were instantly quiet from the get go. I let it idle for 2-3 minutes to see if they would get noisy but they didn't and the engine was just purring over nicely at idle. I didn't reset the ECU or touch anything except opening the bonnet to listen to the tappets.

I then went for a longish drive and the car seemed rather zippy right from the beginning. Still a wee bit of hesitation below 3000 rpm to begin with, but nothing like it was even a day or two before.

Unlike what usually happens where it starts off running ok and then the performance goes progressively down hill the longer I drive it feeling lethargic by the end of the drive, the performance of the car just got better and better the more I drove it, to the point where it was going like a rocket with almost no hesitation after 20 minutes or so driving.

What was really apparent is just how much more responsive and grunty it was in the 2000-3000 rpm range, where it was often suffering from lack of power and quite bad throttle lag before, where you could floor the pedal and time a half second delay on a stop watch before it responded! Today, especially after the first 10 minutes or so driving, if I was in sport mode at 2500 rpm in 2nd or 3rd if I snapped the throttle down to half way it instantly pushed me back in the seat with no lag whatsoever.

Interestingly when I finished driving a couple of tappets were little bit noisy again despite the performance still being excellent.

I noticed a similar thing with the Wynns additive that I put in with the previous oil - the tappets would be silent right from a cold start but 2 or 3 would eventually get slightly noisy when the engine warmed up, and then be silent again when cold - exactly opposite to what you normally see with noisy tappets. I'll bet anything that when I start the car next time the tappets will be silent when first started but slightly noisy again when fully warmed up. (Anyone have any suggestions for why they might be quieter when cold and noisier when hot rather than the other way around ?)

Of course we all know how intermittent this problem has been, and I did let it idle a few minutes before driving which from past experience often causes it to run better, so lets see how it behaves over the next week or two, but if it continues to run as well or even improve further then I think we might have a diagnosis at last - excessive internal mechanical engine noise triggering the knock sensor! (eg "false knock")

Excessive mechanical noise apparently due to lack of maintenance of the lubrication system both before I got it and in the time I've had it.

If the additive has quietened down the mechanical noise significantly and the knock sensor was previously being triggered erroneously the progressive improvement in performance as I drove would have come about by the ECU sensing absence of "knock" and slowly creeping the timing in the knock retard table forward again. The more I drove it the more the timing would return back to normal, although I could have speed the process up by reseting the ECU.

Since a few tappets were still a little bit noisy when fully warmed up but the performance was still excellent it might not be the tappets but something else in the engine that was a bit noisy...and apart from slightly noisy tappets I wouldn't have said that the engine sounds unusually noisy to the ear either...

The fact that the oil I drained came out completely black after being in for only a month suggests its crying out for a good flush and one or more oil changes to get things back in shape, just like I did to the gearbox. This time I might try using a cleaning/flushing agent before changing the oil to give it the best chance of getting all the crud out.

Could it really be as simple as a poor oil maintenance schedule ? Watch this space...

[addo]

I don't think it's that simple.

[Mandrake]

What's this stuff done then ? By what mechanism has it improved the performance so much ? The change is not subtle. As good as it might be I don't think its powers extend to unblocking cats