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 »

Well on Sunday I swapped the fuel pump over. With a couple of screw drivers, a hammer and lots of care and patience it finally let go and started to unscrew just as I was nearly ready to give up, once the cap was unscrewing the rest of the job was quite easy.

Fortunately the petrol tank was down to the low level warning, even so the level is not that far down inside the tank so getting the pump out (which requires tilting it) without spilling petrol is fun...the threads of the cap were thoroughly greased before refitting so I didn't have much trouble there.

The sad news is it doesn't seem to have done much if anything! :( The first time I started it after changing the pump it started instantly instead of after a couple of revolutions and the idle was rock steady which it hasn't been lately. Initial driving suggested that there was a significant improvement but as sure as the sun rises and sets after a couple of days its settled down into its normal routine of not playing ball.

The only thing that seems to have changed noticeably is that the "surging" of acceleration seems to have gone and the engine consistently has a "power note" to the exhaust sound when accelerating now, that seemed to be lacking sometimes before. So there might have been some improvement but it has by no means fixed all the symptoms.

What I am noticing though is that the engine when revving above 3000 rpm under heavy acceleration is really quite noisy and "raspy" despite lacking in power... which going by past experiences usually means its running on less than 6 cylinders. #-o On the occasions that it has run at full performance the engine becomes quieter and smoother, and "purrs" when revving under load instead of sounding "raspy" as it does now.

The fuel pump has been swapped, the fuel rail regulator has been changed, the injectors have passed a balance test (although many months ago now) the coil pack has been swapped (twice) the spark plug leads were swapped 6 months ago, spark plugs less than 1000 miles ago, compressions were perfect and it STILL seems to be misfiring under load!! #-o

Unless there is a problem with the injector control signal from the ECU then it has to be an ignition related misfire. But what on earth could be causing it ? Sigh.

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

Post by larppaxyz »

Can you give us updated list of all the parts you have replaced?

When was your cam belt replaced?

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

Post by Mandrake »

larppaxyz wrote:Can you give us updated list of all the parts you have replaced?
* Coil pack - twice. First with a new one (although clearance house supplied approx £75) most recently with a S/H one from the car KP broke. For the first 3 days after fitting the S/H coil pack performance was vastly improved, but has deteriorated again.

* Rear bank spark plug leads/cassette - twice. Both brand new, the first one developed a hole in one of the front plug leads where the wire goes through the plastic guide just above the coil pack due to catching on the teeth in the guide - after taping up the hole the performance vastly improved and was flawless for 2 weeks then deteriorated again. The second time I replaced the plug leads a month later the performance did not improve.

* Spark plugs - twice. The first time Bosch FR7DC+, of which two of the rear plugs fouled badly enough to cause misfiring in under 1000 miles. The second set were Bosch FR8KDC which have been in for less than 1000 miles but I fear that they too are probably fouled again now due to misfiring or rich mixture.

* Rear exhaust system, but not the cat.

* Oxygen sensor (new)

* MAP sensor (new)

* Fuel pump (S/H)

* Fuel pressure regulator (S/H)

* Inlet manifold gasket (each time the manifold has been out, usually new but this time I've reused the removed gasket)

* Ignition suppression capacitor.

* The two earth terminals above the coil pack have been replaced.

* Throttle body has been cleaned. (Didn't help with low power, but has made the first 10% of throttle travel more sensitive/progressive)

* All connectors that I can reach including knock sensor connector have been cleaned with LPS1 contact cleaner on more than one occasion.

Tested carefully but not replaced:

* Injectors

* TPS

* Air and coolant temperature sensors.

* Knock sensor (difficult to fully test, but it seems to be "working")

* No back pressure measured in front of the cat when tested a few months ago.

* No oil fouling of the rear spark plug wells.

Suspicions:

* Thermostat may be due, although there aren't any signs of overheating.

* Some intermittent coolant loss if running with the pressure cap tight. The expansion header tank seam leaks under pressure but I don't know if there is another leak like the heater matrix, gearbox oil heat exchanger or head gasket.

Starting to wonder if I could have a small head gasket leak or crack in the head leaking coolant into a combustion chamber... :roll: The car nearly failed its emissions test, if the cat is faulty its most likely either due to running with an ignition misfire, or possibly coolant being burnt causing silicon poisoning of the cat...
When was your cam belt replaced?
Cam belt has not been done.

Before anyone criticises this, I can't justify the expense of changing the cam belt (even doing it myself) when the gearbox is still most likely a ticking time bomb and I can't get to the bottom of its misfire/running problems.

It just means I have two ticking time bombs instead of one! If it breaks, it breaks. :roll:

If I can once and for all solve its running issues, and the gearbox starts behaving a bit better (it's been a little bit flaky lately but I don't know if that is due to the engine misbehaving and misfiring or whether its the gearbox itself) then I might consider doing the cam belt myself - if we end up moving to a house with a garage in the next few months. (Trying hard on the garage front while we look at houses! :) )

addo
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Post by addo »

I've recently become aware of significant blow-by in my engine. It still has good power, but the excess crankcase gas during heavy pedalling makes the antipollution valve sound like a BOV. Very chavvy, but explains also the rapid oil darkening/ageing.

That's been the s**t side of pushing it hard with a blocked exhaust; mild engine damage (a re-ring would sort it, but the head gasket is fine).

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

Post by Mandrake »

Except I don't have a blocked exhaust... ;)

How do you check for excess crank case pressure due to blow by ? Would I disconnect the crank case breather pipe that goes into the bottom of the throttle butterfly assembly and check for pressure from it when revving the engine ? Should there be no pressure at all under normal circumstances ?

Driving home today the car felt decidedly like it was two cylinders down under anything but very light throttle...raspy engine note when revving and very lacking in power.

In the back of my mind I can't help wondering if there is an intermittent problem with the injector or coil primary control from the ECU, and given that I've ruled so much else out yet it stubbornly continues to misbehave I think it may be time to crack open the ECU and check for dry joints, particularly on the main connector and the output transistors that drive the injectors and coil primaries.

Has anyone had the ECU from an ES9J4 apart, and what's involved in getting it apart and back together again safely ?

I'm a confident and experienced solderer with good electronics experience, however I'm always a bit cautious about opening something expensive / hard to replace like an ECU when I don't know what snags I might run into that could leave me with a non working car. I assume it has some sort of water tight gasket or sealant ?

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

Post by dnsey »

Yes, very wise to find out how it's assembled first.
I recently repaired a C5 cooling fan ECU (!) - faulty o/p transistor, but couldn't find any way of getting the power devices back into the heatsink, which formed part of the housing, on re-assembly.

addo
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Post by addo »

The ECUs open up very easily; you'll find it surgically clean inside so do this indoors. There is also nothing likely to be wrong with it. I would photograph the inside after dating my ingress inside the lid with a marker pen.

Blowby on a worn motor is easy to detect by feeling a stronger "putter" of air out the dipstick tube than for a healthy motor. That said, an ES9 running on four will still feel strong; it will have a noticeable misfire but no shortage of power/torque.

Cambelts - the only failed cambelt car seen with my eyes, I suspect was a misfitted replacement kit. I'll probably never hear the whole true story.

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

Post by Mandrake »

I agree its unlikely the ECU is faulty but this has been such a wildly intermittent and insolvable problem that it needs checking. The intermittent nature of the problem does have all the hall marks of dry joints.

Have you driven an ES9J4 running on four cylinders ? What ever is wrong with it is not leaving it with "no shortage" of power, its well below the performance of my old 2 litre automatic when its misbehaving at its worst, such as it was yesterday. Its a massive reduction in power. Comparing it to my 125HP 8 valve 2 litre I'd say the power must be dropping down to around 100-110HP when its really misbehaving.

The large loss of power and the fact that its a waste spark system AND fires injectors in parallel in 3 pairs makes me think the potential for a pair of cylinders to misfire at the same time is quite high. (For example a primary coil feed fault or injector feed fault will take out two cylinders)

addo
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Post by addo »

I've driven a PRV with leads left off (my fault). It still shifted, just ran horribly at low speeds.

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Re:

Post by Chris570 »

addo wrote:I've driven a PRV with leads left off (my fault). It still shifted, just ran horribly at low speeds.
I've driven an ES9 with a dead coil and it was sounding awful, almost lawnmower-esque. The power drop is massive and you really feel that without booting it it won't go up hills.

maybe it's the autobox that is the difference but yep, an ES9 with 2 cylinders down is gutless

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Post by addo »

Could be; the PRV had the 4HP18 which is all mechanical.

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Mandrake
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Re: Re:

Post by Mandrake »

Chris570 wrote:
addo wrote:I've driven a PRV with leads left off (my fault). It still shifted, just ran horribly at low speeds.
I've driven an ES9 with a dead coil and it was sounding awful, almost lawnmower-esque. The power drop is massive and you really feel that without booting it it won't go up hills.
You've pretty much described the exact symptoms I'm seeing (intermittently) at the moment.

Noisy, raspy engine note when revving under load, massive power loss to the point where you do need to boot it to get up hills at any decent speed or even just to keep up with the traffic.

Now imagine that its actually running on 6 cylinders at idle and very light throttle but dropping back to 4 cylinders as soon as you open the throttle much and put it under any significant load. (voltage demands at the plugs go up with pressure)

Classic symptoms of a weak spark IMO, and if the cause of the weak spark is primary side on one coil then its going to cause two cylinders to have a weak spark that may fire at idle but miss as soon as the engine is under load.

Can't be coil pack, I can't be that unlucky with three different coils. Can't be plugs and leads because they've been done twice. If its an ignition misfire its got to be weak primary current due to an ECU fault (dry joints maybe) or wiring/connectors from the ECU to the coil pack.

The only way to be sure would be to measure the primary current waveforms to the coil pack, something I have NOT done yet. Trouble is I'd need a decent current probe, something like the PP218 or PP264 from Pico:

http://accessories.picotech.com/current-clamps.html" onclick="window.open(this.href);return false;

They're not cheap though. :( There are cheaper ones but usually they have too much of a "snub nose" where the wire goes in to clear the tight spacing between the wires at the coil pack plug.

By the way I came across this today and thought Christmas had arrived early:

https://boschelectronicservice.eu/uk/sp ... 0261206119" onclick="window.open(this.href);return false;

Brand new (or refurb?) ECU's for the ES9J4 from Bosch for 49 Euro's, un-programmed. :shock: (ready to program to the CPH with a Lexia)

Then I read the bit at the bottom that says its the MANUAL version of the ECU not the Automatic version... #-o Oh well.

Would be ideal for David Hallworth's Activa V6 conversion though - the whole thing ready to fit and pair to the CPH would be cheaper than the cost of getting an existing S/H 406 coupe manual ECU unlocked!

If I could find an un-programmed Auto version of the ECU for the same price I'd snap it up...

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

Post by larppaxyz »

When was your cam belt replaced?
Cam belt has not been done.
My cam belt has 70000 miles / 110000 kilometers on it. It still looks ok and i have it replaced next week. But i'm thinking, could stretching of cam belt or wobbly belt tensioner cause problems? Some engines that have chain instead of belt can suffer badly from stretching, not sure if this is the case with belts too.

That's why i'm asking how many miles you have done with your belt.

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

Post by Mandrake »

larppaxyz wrote:
When was your cam belt replaced?
Cam belt has not been done.
My cam belt has 70000 miles / 110000 kilometers on it. It still looks ok and i have it replaced next week. But i'm thinking, could stretching of cam belt cause problems? Some engines that have chain instead of belt can suffer badly from stretching, not sure if this is the case with belts too. That's why i'm asking how many miles you have done with your belt.
When I say the cam belt has not been done, I mean it has not been done by ME since I've owned the car.

It might or might not have been done by a previous owner but I have no records of any past servicing of the car let alone cam belt. I bought it at 99,500 in March last year and it has now done 105,500.

I wouldn't have thought the belt could stretch far enough to affect engine performance dramatically without breaking ? There is certainly a risk of it breaking though if it is the original.

addo
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Post by addo »

It's simply not possible for the belt to cause your problems.