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

[Northern_Mike]

I think another item would become the focus of similar trials and discontent.

Not if it were something sane with a reasonable sized engine, a manual gearbox and steel springs. Dross like that can be tolerated while they get a place of their own, funds in the bank and it won't be a constant, heavy drain on resources. I've bought reasonable cars with tax and MOT for what's been spent on gear oil and exhaust bits that car.

[addo]

It may not even be a car that takes the place as item of discontent.

[Northern_Mike]

It may not even be a car that takes the place as item of discontent.

Then at least he'd have a car he could trust to go for a long drive to escape whatever that item of discontent may be.

[Mandrake]

Getting a bit overdramatic here aren't we guys ?

The gearbox additive and flush is already on its way (although it will be a couple of weeks before I get a chance to use it) lets see what it does before we consign the car to the scrap bin. The fact is I'm very sensitive to small misbehaviours of cars, what I notice passengers in the car don't, they all wonder what all the fuss is about when everything seems to be working fine, and in a sense they're right, the symptoms are subtle but I notice them and worry about them given the reputation of the box, and too much understanding of what goes on inside the box...

If it was a more lowly Xantia I would have given up on it long ago, but the V6 is the Xantia I always wanted to get in 2005 when I ended up with a 2 litre simply because there were too few in NZ (only 300 sold) and they were twice the price I could afford. If I dump this one now chances are very good I will never get another one before they are simply too old to maintain. (Arguably they're just reaching that point already)

Have faith guys, apart from the leaky banjo and the time the exhaust broke (which can happen to any 15 year old car with a rusty exhaust system) the car hasn't let me down yet...

[CitroJim]

Have faith guys, apart from the leaky banjo and the time the exhaust broke (which can happen to any 15 year old car with a rusty exhaust system) the car hasn't let me down yet...

And it's better the devil you know than abandoning this one and taking on something else. All you ever do is end up swapping one load of grief for another. I know from hard experience. Also the load of grief you swap it for may well be more grief than the old. had that too..

Remember that cars are never sold because they're in perfect condition. Almost always there's some nasty gremlin just waiting to smile at you when you least expect it...

Been there too many times... I speak from hard experience. I have only ever been lucky in buying absolutely faultless second-hand cars on two occasions and I still have them. And one of them is not the XM!!!

Mainly I used to buy cars with faults with eyes wide open. I've brought far sicker ones than yours back to health Simon...

My days of buying problem cars are now over for good. I have what I want and I'm sticking fast....

..Unless an absolutely pristine late XM V6 comes on the market

[Northern_Mike]

Getting a bit overdramatic here aren't we guys ?

Not really. This thread started near as damnit 9 months ago, you have tried many, many things, and the car is still not right, and has a dying gearbox. I'm sorry? Nine months?

[Northern_Mike]

Mainly I used to buy cars with faults with eyes wide open. I've brought far sicker ones than yours back to health Simon...

You have Jim, but you have the facilities and a perversion for repairing knackered auto-boxes..

[addo]

Some people have a sort of mechanical confidence; they'll cross that path of no return on a job without having sighted the road back.

I'm mostly like that, I think Jim is the same. Have worked with another fellow also of that bent (it was unnerving when he pulled on of my tools apart just to see how it worked).

[Mandrake]

Getting a bit overdramatic here aren't we guys ?

Not really. This thread started near as damnit 9 months ago, you have tried many, many things, and the car is still not right, and has a dying gearbox. I'm sorry? Nine months?

Yes but this thread hasn't been all about the gearbox, it started off about the broken exhaust and morphed into a catch all for any and all problems relating to the car...

I've spent far far more time under the bonnet trying to troubleshoot engine issues than I have gearbox, and largely succeeded too, although it did take a long time to get there.

I've spent 100x times as much time thinking about and writing about the gearbox on the forum than I have actually spent time on the car working on the gearbox... at the end of the day all I've actually done to it is changed the oil a number of times. A relatively easy job compared to even handbrake cables or taking the inlet manifold off, so I've probably spent a total of 6-7 man hours under the bonnet working on the gearbox in total.

I'm the sort of person who likes to think a lot about problems and analyse them over and over in my head, its just what I do, and some of that thought process gets aired on the forum...

I think I have a different opinion about what a car is than you do to, I'm sure I read in another thread that you've had over 100 cars ? I've been driving for 22 years and I'm only onto my 5th car, so to me a car isn't a toy that is disposed of at the first sign of trouble. All but one of my cars has been well over 10 years old when I bought it so old cranky, needy cars is nothing new to me

[Northern_Mike]

If it was a more lowly Xantia I would have given up on it long ago, but the V6 is the Xantia I always wanted to get in 2005 when I ended up with a 2 litre simply because there were too few in NZ (only 300 sold) and they were twice the price I could afford. If I dump this one now chances are very good I will never get another one before they are simply too old to maintain. (Arguably they're just reaching that point already)

I always wanted a classic Impreza. I bought one. It was nice. It needed work. It was mechanically soundish, but needed work.

Now, I could have spent months getting it right... or, as I have done, sold it for what I paid for it, and I'll put that money towards a later, better one when one comes around. Easy really. For sure, I won't be messing around repairing the same fault in 9 months..

[Northern_Mike]

I think I have a different opinion about what a car is than you do to, I'm sure I read in another thread that you've had over 100 cars ? I've been driving for 22 years and I'm only onto my 5th car, so to me a car isn't a toy that is disposed of at the first sign of trouble. All but one of my cars has been well over 10 years old when I bought it so old cranky, needy cars is nothing new to me

Yes, I've had over 100 cars. 130 to be precise. I'm not sure what difference this makes, as the cars I would count as our "family" cars, which we've kept for years as kiddie buses, well, there's been, erm, A Rover 416GSi (4 years) a Mondeo MK1 (6 years), A 306 Diesel Turbo (3 years) and the Berlingo (2 years and counting). All have been kept and well maintained for years. So, actually less serious cars than you over the 24 years I've been driving..

The other cars have simply been toys, because it's a hobby. I find it interesting to drive different vehicles. They get maintained properly and in some cases repaired, then sold when I get bored of them.

[CitroJim]

Mainly I used to buy cars with faults with eyes wide open. I've brought far sicker ones than yours back to health Simon...

You have Jim, but you have the facilities and a perversion for repairing knackered auto-boxes..

True Mike, true. First time I've ever been described as a pervert

I'm the sort of person who likes to think a lot about problems and analyse them over and over in my head, its just what I do, and some of that thought process gets aired on the forum...

Same here, all part of the fun for me and part of what keeps me going, gets me up in the morning and keeps me sane...

Now, I could have spent months getting it right...

And that's the other part that keeps me going, gets me up in the morning and keeps me sane... It's one reason why I have an XM and in the past have always had a project on the go. neither of my two Xantias can fulfil that role as they're both good and need little doing to them... The XM, sadly, is rapidly getting there

[Mandrake]

I don't have oscilloscope so testing it with cut wire would be my only option. I would love to hear what your oscilloscope shows . In theory you could make gear changes faster by manipulating this signal.. but thats different story (you could use Arduino and few lines of code to do this).

The other day I got a chance to put a scope on the torque reduction control line between the gearbox and engine ECU during a test drive. Here was the setup:



Getting the cover off the engine ECU connector to back probe the connections is difficult but not impossible. Once its slid off you can get at the back of all the terminals quite easily.

I learnt some useful info about this control signal.

1) There are no analog ramp components to this signal as implied by the diagrams in the training manual, its a simple high/low digital signal with steep rise/fall time.

2) The polarity is opposite to what I assumed, and the voltage range is greater. LOW voltage is no torque reduction, found during normal driving except while changing gears. I measured 0.4v in this state. HIGH voltage is a torque reduction command, which occurs for about half a second during an UP shift. I measured 10.4v for the high state.

3) The torque reduction (high voltage) state lasts the entire duration of an up shift, or about 0.5 seconds roughly, and corresponds to the time when you hear the engine note become quiet, thus confirming the torque reduction.

4) During a down shift there is no long torque reduction pulse, there are two very narrow pulses (less than 10ms each) at the start of the downshift, and another two very narrow pulses at the end of the down shift. I didn't bother to measure their exact pulse width. I believe these very narrow pulses are used to signal to the engine that a down shift has occurred so the engine can keep track of which gear the gearbox is in, even though a torque reduction is not required for a down shift. (The torque reduction line is also used to signal to the engine ECU which gear the gearbox is in)

5) In neutral the torque reduction line is permanently high eg 10.4v, which corresponds to torque reduction. I believe this is done as part of the idle speed compensation, the engine ECU interprets a permanently high reading as neutral, thus allowing it to synchronise its recognition of neutral with the gearbox. (to recognise 1st through 4th it then counts torque reduction commands that occur at each gear change, a long pulse for up shifts, narrow pulses for down shifts)

6) I could not see any problems at all with the torque reduction signal on my car during the testing period. The performance of the car was a little bit intermittent during the test, sometimes sagging at low RPM but the signal was still fine. I never saw the signal go high during driving except during a gear change.

Thus I think we can rule out problems with the gearbox torque reduction control signal as a cause of poor low RPM performance. Remember though that the knock sensor can also retard the timing by just as much as the gearbox torque control line, so my hunch is that any excessive timing retard resulting in poor performance must be due to knock sensor activity.

In unrelated news I've just got a MPG figure for recent driving, I had to do a couple of partial top ups due to lack of money so this is the first full top up in a month or so that has allowed me to calculate the MPG.

Over 406 miles of which 80% will have been low speed, short trips (untold trips between two houses and the dump while moving) I averaged 21.7 MPG. Not quite as good as the 22.9MPG I managed last time but a lot better than the 19MPG I was averaging on the 95 octane fuel. So I think its pretty safe to say that yes the ES9J4 does do significantly higher MPG on 99 octane fuel than 95, with me achieving at least 2.7MPG better in around town running...

I never ever managed more than 19.8MPG in around town driving on 95 octane fuel, now I'm getting consistently 21.7 or more on 99 without changing my driving style at all.

[addo]

A lot of gearbox/engine ECUs limit either fuelling or revs when in N, to stop people doing "clutch dumps" whether by free will or ineptitude. The AL4 simply makes you wait before it engages D again, if you spin it up too hard.

It also makes sense that the "normal" state is no applied trigger voltage, this means that a minor control failure doesn't necessarily cripple the driveline to excess; after all you still have the rev limiter. That sort of design approach is common with non-redundant control systems.

[Mandrake]

Yep, it looks like the engine idles with retarded timing when in neutral and as soon as you engage drive the torque reduction retard signal is removed, giving a small instant boost to the engine torque as part of the idle speed compensation for torque converter drag in drive. (Rather than just relying on the feedback loop between crank speed sensor and idle control valve, which would cause a big sag in idle speed with a delayed correction)

The 4HP20 training manual says that it signals the engine ECU to help with idle regulation when going between drive/neutral but it doesn't detail exactly how or by which control line, it looks like the torque reduction control line is the one used to achieve this.