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

[Mandrake]

I've met with Simon and worked on his car - he's more than competent to fix this, and if it was something simple he'd have fixed it by now. OK, he likes to write (at length!) about it, but that's his perogative

Thanks for the vote of confidence Richard, yes I do write far too much, thinking aloud is just the way I operate, especially when tackling such a challenging problem, but I'll have to cut it down a bit as it clearly bothers some people...

It's not something simple (at least not simple to find, the repair itself might be simple to implement) and it hasn't been a single thing on its own either. I think the biggest problem I had right from the beginning is that I was never dealing with just one fault, I'm sure it was a confluence of multiple things, but I was searching for one fault that explained everything, and that was my initial undoing.

I know now for a fact that both the gearbox and engine developed problems within a month of each other - the 1500 rpm groan I first reported in this thread turned out to be the gearbox, while the low rpm rough running is obviously the engine.

I think what happened was that the car had done very low mileage in the year or two before I got it (I know from the on-line MOT test figures that Alex only did about 800 miles in the 9 months he owned it, and the previous owner didn't do much either) and had been neglected for maintenance. When I got the car it suddenly went from <1000 miles a year to about 5000 miles a year, and got driven relatively hard including a long hard working 4 day 800 mile tour around Scotland. Only 6 weeks after that trip multiple symptoms started to appear. Co-incidence ? I think not. I think the sudden hard driving and increase in mileage brought a number of latent faults to the surface at around the same time.

Then there have been the introduced problems along the way - like being supplied the wrong oxygen sensor despite trying my best to get the correct one, obtaining a second hand coil pack that turned out to be faulty and worse than the one in the car, fitting brand new but faulty spark plug leads, fitting new but incorrect spark plugs that then fouled because they were too cold and so on...it has been tricky to try to untangle all these separate threads with limited resources at my disposal and figure out what is cause and effect but its finally looking like I nearly have this mess untangled and pared back to a single remaining problem. (Unexplained lean running under low rpm load)

[Mandrake]

I have *never* seen an improvement using branded fuel in the Berlingo, in fact, I can honestly say the best mpg I got from it, 51.4, was on Asda fuel when we went down to Cornwall in it last year.

Being a competent driver, and being able to drive economically makes far, far more difference than changing fuel will ever do. That's if it makes any at all.

Mike you drive a Diesel. Diesel engines aren't fussy about fuel Cetane rating in the same way petrol engines are fussy about Octane. As far as I know, Diesel engines don't have knock sensors that adjust injection timing based on engine knocking the way petrol engines adjust ignition timing based on knock feedback. So your Diesel engine anecdotes are not applicable to a petrol engine.

The ES9J4 is a fairly high 10.5 to 1 compression ratio engine tuned for 98 octane, it relies heavily on knock sensor feedback based timing retard to run acceptably on lower octane. Retarding the timing reduces efficiency and requires a heavier foot to maintain the same speeds especially at lower rpm, which means more fuel burnt and lower MPG to drive with the same degree of vigour.

Change in MPG with Octane on a car capable of utilising the higher octane by increasing timing advance is very real. I could never crack 20MPG in slow around town driving even when the car was running perfectly, as soon as I switched to 99 I was consistently seeing 22-23MPG in the exact same conditions, even though by then the car wasn't running as well as it should be. Low down torque and responsiveness was also significantly better. I did the sums and the increased MPG actually paid back the increased fuel cost and then some, plus I ended up with a more responsive and driveable car.

On another car with a lower compression ratio that doesn't need the higher octane the difference in performance would be nill so higher octane would be wasted money.

[Northern_Mike]

I have *never* seen an improvement using branded fuel in the Berlingo, in fact, I can honestly say the best mpg I got from it, 51.4, was on Asda fuel when we went down to Cornwall in it last year.

Being a competent driver, and being able to drive economically makes far, far more difference than changing fuel will ever do. That's if it makes any at all.

Mike you drive a Diesel. Diesel engines aren't fussy about fuel Cetane rating in the same way petrol engines are fussy about Octane. As far as I know, Diesel engines don't have knock sensors that adjust injection timing based on engine knocking the way petrol engines adjust ignition timing based on knock feedback. So your Diesel engine anecdotes are not applicable to a petrol engine.

The ES9J4 is a fairly high 10.5 to 1 compression ratio engine tuned for 98 octane, it relies heavily on knock sensor feedback based timing retard to run acceptably on lower octane. Retarding the timing reduces efficiency and requires a heavier foot to maintain the same speeds especially at lower rpm, which means more fuel burnt and lower MPG to drive with the same degree of vigour.

Change in MPG with Octane on a car capable of utilising the higher octane by advancing its timing is very real.

I own two petrols and a diesel Simon. Do get the facts right before you start patronising me.

The effect is not "very real". It's a placebo effect, or the driver changes his style of driving unconsciously to compensate for the extra spend.

Please bear in mind that I used to rebuild, Saab 900 Turbo 8 and 16s and modify the ECUs (when modifying an ECU needed a soldering iron, not just a remap! )- one of the first cars to use a knock sensor to advance/retard the timing when needed, so even though I sold my last one 10 years ago, I know a bit about the subject. Driven normally, there was no difference in consumption. The only difference was that with high-octane fuel then the boost could be turned up further and the boost rise rate made faster. Much the same effect is seen on the Imprezas I had too.

My V6 is returning an average of 28.2mpg on Asda fuel at the moment.

StevieB told me to fill my car with branded fuel. He didn't specify diesel or petrol. He just said "branded fuel". If you wish to move the goalposts to suit your theories every time someone contradicts them, go ahead. It doesn't bother me.



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[lexi]

Ach!..........C'mon guys. We are all different. Vive La Difference!!

Addo..........confrontational? Nah, he's just been out in the sun too long with that nailgun

[addo]

I don't know if there are any "low compression" petrol engines sold now in the first world (excluding forced induction).

One of my most brutal tests involved twenty five litres of year old (probably older!) premium fuel in an empty tank. Just the slightest increase in roughness when accelerating solidly, somewhat worse consumption but no stuttering, no staggering.

[addo]

Lexi, you know I'm a repressed slater. Who besides you and I, knows what a duchess is, or a zax?

[Northern_Mike]

Zax is a hatchet thing for slates isn't it? No idea what a duchess is though.

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[Mandrake]

If an injector cleaner was so marvellous it changed the running of a car from good to better, or from bad to good in just one application, it would be immensely strong! You only have to put an injector under the stream from a parts washer nozzle to see how long it takes to start lifting varnish, and that's without combustion putting it back on.

I think I might have an idea why injector cleaner could cause an immediate change that only lasts for the duration of the application. (Other than possibly affecting the octane, which shouldn't be a factor if the fuel is 99 RON to begin with)

When I was flow testing the second hand injectors in the shed before fitting them I did at least a dozen different carefully controlled balance tests in various conditions. (Fuel pressure gauge, electronic injector pulser, regulated 12v power supply etc) A number of those tests were with pure petrol, later tests were done with a strong mixture of Redex in the petrol mix. (Roughly 20x the normal tank application strength to be fair)

I did a test immediately before adding the injector cleaner to the mix and again immediately afterwards - we're talking about 2 minutes later. The pressure drop test before adding it was from 38 psi to 24 psi - all six injectors balanced within a fraction of a psi. The test immediately after adding the injector cleaner to the mix was 38 psi to 18 psi, all six injectors balanced within a fraction of a psi. Nothing else was changed. All the pure petrol tests were consistent with each other, and all the petrol + injector cleaner tests were consistent with each other too.

If you compare the before pressure drop of 14 psi to the after of 20psi, that's a staggering 43% increase in flow volume for the same injector pulse times! True, this was at 20x the normal mixture strength, but it is clearly affecting the mechanical properties of the fuel (viscosity ? friction ?) such that the flow rates were increasing for otherwise controlled conditions.

Now consider that we're talking about only a 10% flow increase to go from a too lean mixture to a rich mixture (think about open loop mode with its largely predefined parameters) and a more normal dose of injector cleaner could conceivably be increasing the flow rates of the injections several percent even though its not cleaning them because they're not actually dirty. As soon as the injector cleaner is used up and a tank of normal petrol with no additive is used, flow rates go back to where they were before. So there is no permanent improvement - it only lasts while the "cleaner" is in use.

This is consistent with what I have observed - the car runs obviously better with a strong (2x normal) dose of injector cleaner in the tank, but if I don't add it with the next tank it goes back to how it was very quickly.

I think this is further evidence for my "lean under load at low rpm" hypothesis - for some unknown reason the mixture is lean in open loop mode at low rpm under load, if adding the injector cleaner in a strong dose temporarily bumps the flow rates of all the injectors up by say 5% taking the engine from marginally lean to marginally rich then that will be very noticeable. If the mixture was already as rich as it should be there would be no noticeable difference, in fact possibly just a reduction in MPG due to running richer than necessary.

It's no more of a cure than disconnecting the canister purge line - only a further clue that a lean mixture is the problem!

[addo]

Correct!

The duchess is a size of slate: http://www.penmorfa.com/Slate/sizes.htm" onclick="window.open(this.href);return false;

Slate is beautiful; it kills me that we have next to none in Australia to use. All the old slates here came out as ballast, the ships went home filled with produce. Same way we got Marseilles tiles. There are some early captain's logs where they complain the ship is sailing sluggishly after leaving Australia, then they take on fresh limes in Papeete and progress speeds up.

[Mandrake]

I own two petrols and a diesel Simon. Do get the facts right before you start patronising me.

Sigh. You specifically said you noticed no difference in what fuel you used in your Berlingo - which is a Diesel engine and has absolutely ZERO to do with how much fuels affect a petrol engine! So why even mention it. If you had a recent petrol engine anecdote then why not share that instead instead of irrelevant stuff.

The effect is not "very real". It's a placebo effect, or the driver changes his style of driving unconsciously to compensate for the extra spend.

Complete nonsense Mike, this is getting very tiresome indeed. Now you're patronising me. I have a log book of every fill up I've done on this car since I owned it. I could not, no matter how gently I drove exceed 20MPG on my normal weekly routine right from the day I bought the car. Never. Zip. Nada. The very next fill up after switching from 95 to 99 it did 22.7MPG and I was NOT compensating for anything. If anything I was driving in a more spirited manner because the car was that much more willing and lively at low rpm. I never went into it with a preconceived notion that the MPG would increase - it was a pleasant surprise, not an expectation. The following 3-4 months I was getting between 22-23MPG every month.

Please bear in mind that I used to rebuild, Saab 900 Turbo 8 and 16s and modify the ECUs (when modifying an ECU needed a soldering iron, not just a remap! )- one of the first cars to use a knock sensor to advance/retard the timing when needed, so even though I sold my last one 10 years ago, I know a bit about the subject. Driven normally, there was no difference in consumption. The only difference was that with high-octane fuel then the boost could be turned up further and the boost rise rate made faster. Much the same effect is seen on the Imprezas I had too.

And what is the compression ratio of the Saab ? Given that it's a turbo it will be MUCH lower than 10.5, so again, you're drawing an irrelevant comparison between two very differently designed engines.

All you're doing is being argumentative for its own sake and I'm getting kind of sick of it to be honest. If you don't have anything constructive to contribute to the problems at hand in this thread I do suggest that you un-subscribe.

[Hell Razor5543]

Ever since the issue with Tesco fuel damaging sensors (IIRC it was silicon affecting the lambda sensor) I have always used branded fuels in my personal cars (Shell by preference, as there is one only 2 miles away). However, with my employer I have been asked to keep costs down. My fuel card is a Texaco Fast Fuel card (but some Texaco stations won't accept it, as it can take a month for Texaco to make payment to their own petrol stations!), and I normally use Murco or Morrisons.

[addo]

kv of the fluids is probably your key to those different results - you're not squeezing them hard enough to add significant heat. It's well possible the cleaner has a surfactant added, this would help its action and also the characteristic you noticed.

I also find it intriguing how much fuel is trapped in an injector - very deceptive.

The additive which I've seen contribute the most to buildup may not be used in the UK - it's MMT, and is also used in some "octane boosters". America often adds it to winter fuel in the colder states.

[Northern_Mike]

[/quote]
And what is the compression ratio of the Saab ? Given that it's a turbo it will be MUCH lower than 10.5, so again, you're drawing an irrelevant comparison between two very differently designed engines.

All you're doing is being argumentative for its own sake and I'm getting kind of sick of it to be honest. If you don't have anything constructive to contribute to the problems at hand in this thread I do suggest that you un-subscribe.[/quote]

You're doing it again. Compression ratio in the Saab was 9.1. Yes, less than 10.5. but running 1.6 bar boost.

Knock is knock. The effects are the same, the ECU was designed to counteract knock, change timing and back off the boost.

Let's face it. You haven't added anything constructive to the thread for about 80 pages, though you do like patronising and pooh-poohing everyone else.

I would unsubscribe, but the forum software doesn't really allow it. Nor does it block effectively....

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[Mandrake]

Let's face it. You haven't added anything constructive to the thread for about 80 pages, though you do like patronising and pooh-poohing everyone else.

I would unsubscribe, but the forum software doesn't really allow it. Nor does it block effectively....

Thanks Mike, I've saved you the trouble. You're now on my block list. Have a nice day.

[Mandrake]

Simon .... fwiw i dip into your thread on an irregular basis and, while finding it hard reading, being extremely verbose at times, I would not think to post any unconstructive comments as to its content, which after all is entirely your remit, as appears to have been happening recently. I say carry on, it makes for a constructive log on the state of YOUR car. It is yours to do with as you please and, as my car is similar in all respects to yours i find it extremely educational . In much the same way that contributors are being asked to unsubscribe can i ask that you yourself also ignore all irrelevant and destructive posts. Any replies are only adding fuel to, what would otherwise be, a dwindling fire in my opinion. Just keep on topic and i'll continue to read and enjoy. Thanks!

You're right about the blog aspect of this thread - it has inadvertently become a long and detailed record of the trials and tribulations of this car and would be better placed in the blog section. Is there a moderator who would like to move it to the blogs section for me ? I'll try to cut down on the massive posts and maybe spread multiple ideas across multiple posts so its a bit more digestible.

Despite comments to the contrary there is still a lot of good information in this thread in the last 80 pages, if anything the latter half of the thread is more useful as I've learnt so much in the time this thread has been going that its painful to look back and read the first few pages now and see how little I knew when I began hunting these problems. So this thread is also about my journey to understand things better and bring myself up to speed on the functioning and troubleshooting of this engine and gearbox. I didn't even know where the map sensor was, what fuel trim was or how an oxygen sensor worked at the start of the thread! (I learn quickly though)

It has been diluted with a lot of off topic chatter, ribbing and heckling in recent times though which is frustrating to say the least. To some people it might be a game to poke fun here but to me its a serious effort to solve this car's problem and I don't have a better place to discuss it. I also want it documented to save anyone else the hair pulling that I've been through - if I do nail it 100% I will be detailing exactly what the problem(s) were and the best way to troubleshoot and identify them without reading through a 107 page thread!

Those of you who are fed up with this thread, feel free to leave, or at least keep quiet. Those of you who are genuinely interested in helping solve this tough nut or are just interested bystanders who are curious to know "whodunnit" in the final analysis read on. A few more months and I'll be moved into a house with a driveway and a garage anyway so my ability to troubleshoot will improve exponentially compared to my current situation of working in the open on the pavement!

That's if I don't lick it before then of course.