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 »

lexi wrote:
the audio forum I frequent has many many threads that are well in excess of 100 pages -
That'll be DIY Audio where obsessive students argue about "the sounds of cables" and full range drivers with Enabled dot patterns on them? :lol:
Yeah that's the one, although I avoid those two topics :twisted:
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by Mandrake »

larppaxyz wrote:
Mandrake wrote:
larppaxyz: does yours do this too if you quickly tap the throttle ?
Not quite like that, but thats exactly what it does sometimes when i'm just idling.

Now that i have been thinking this TPS issue (and watched some youtube videos about TPS problems and reading some articles) i think my lower end (idle part) of TPS is open circuit most of the time and ECU detects this and ignores or calibrates TPS more or less randomly because of this. I haven't seen any error codes about TPS, but maybe they get clearead everytime ECU detects TPS is ok again, or maybe it's not bad enough to trigger code.
Yes I think that's exactly what happens. An intermittent dead spot that makes the wiper connection go open circuit at some locations. With these types of inputs the ECU is self calibrating - minimum and maximum throttle are not at the extremes of the potentiometer range, they're about 1v and 4.5v respectively, the ECU learns this over time by observing the minimum and maximum voltages seen during operation.

If it never sees a voltage under 1v then 1v is calibrated as idle / closed throttle. Then if the voltage suddenly drops to 0v due to the wiper going open this represents a "less than idle" throttle opening - the initial response is to cut back fuelling and the engine attempts to stall, (you can actually hear it cut out completely on mine) when the rpm gets dangerously low the anti-stall function kicks in and the ECU opens the ICV and boosts the fuelling - the idle then surges above normal as my video showed.

As you say, sometimes this surging behaviour can happen with the throttle closed. Mine hasn't done that recently but it was doing that surging at idle after a hot start quite a lot until recently.

If the 0v reading persists after a few surge and stall cycles the ECU recalibrates the TPS input to accept 0v as the new closed throttle position. This means you now have a large discontinuity in the calibration at the bottom end of the throttle range, (if its only open circuit close to the bottom) and the scaling of the entire throttle range will be thrown way out.

Once this bogus recalibration happens I believe poor low rpm performance and throttle response occurs until the ECU is reset.
Anyway, it's 5min job max to replace TPS on my Pug, but i have no quick access to (new) replacement part. I'm thinking about opening up my TPS (i know it's glued/molted, but should be possible anyway) to clean it and just slightly twist those "legs" that are in contact with "resistance" part. I will do some resistance measuring and visually inspect it. I assume construction is similar to this http://www.4crawler.com/4x4/CheapTricks/TPS/tps2.gif" onclick="window.open(this.href);return false; (this is however 4-wire version).

I don't know why, but i have feeling this could be it finally :) (Yeah... right)
I don't think its a good idea to try dismantling your TPS, if it breaks your car is off the road... :?

Although a lack of wiper tension could be the problem, on a carbon track potentiometer the usual failure mode is the carbon track itself wears out at points where the potentiometer spends a lot of time - for example at closed throttle. In that case tensioning the wiper won't help.

Will that ebay seller I linked to not ship to your country ? (Where are you again ?)

If you're really stuck and can't find one for a good price anywhere let me know and I could get another one from the same seller and post it to you if you're willing to pay the extra postage...(I have no idea what the postage would be but its very small and light and would fit in a bubble bag)
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Post by addo »

I am fortunate to have a good set of limbs, a clear head and a lovely country. Why the hell any able-bodied person would want to essentially jail themselves for so long as is required to obtain value from expensive audio gear, I cannot understand. You don't even get the frisson of a trip into town to see a band, orchestra, ensemble etc.
lexi
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by lexi »

You have a point Addo. It is all time spent sittin on yer jacksie!
However we have long dark winters here and we cannot make love every night?.........our wives would kill us! :lol:
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by falling-out-with-my-car »

out of my depth again.
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myglaren
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Post by myglaren »

addo wrote:I am fortunate to have a good set of limbs, a clear head and a lovely country. Why the hell any able-bodied person would want to essentially jail themselves for so long as is required to obtain value from expensive audio gear, I cannot understand. You don't even get the frisson of a trip into town to see a band, orchestra, ensemble etc.
True as far as it goes. I would love to go to concerts but can't anymore, the last two attempts were an unmitigated disaster, never got to see or hear anything, unfortunate as there are some excellent venues within a 20 mile radius.
I would travel to the USA to see Jackie Evancho live, and live in penury ever after. Never going to see her unless she comes to my house to sing - unlikely I think.

So it's the hifi or nothing unfortunately.

Yes, I'm a member of the DIY Audio Forum too - largely inactive. Joined for info on a Sonab system but that soon petered out.
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Re:

Post by Northern_Mike »

addo wrote:I am fortunate to have a good set of limbs, a clear head and a lovely country. Why the hell any able-bodied person would want to essentially jail themselves for so long as is required to obtain value from expensive audio gear, I cannot understand. You don't even get the frisson of a trip into town to see a band, orchestra, ensemble etc.
I agree wholeheartedly with you Addo. There's some venues I'll avoid as I don't like the acoustics, and pubs with decent bands on here are often too crowded. Have only been to two in the last year oddly, at opposite ends of the spectrum - Buena Vista Social Club at the Royal Albert Hall, and the original Status Quo reformed at Wembley arena. Both damn good. My brother's in a a gigging pub band, and I've spent a fair amount of time humping gear about and sat behind the 32-channel desk being annoyed by drunk people. All good fun.
Stempy
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by Stempy »

You know, if you feed the LT side of an ignition coil from the speaker output of an amplifier you can make a spark plug attached to the HT side dance to the music.....
larppaxyz
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by larppaxyz »

Mandrake wrote: I don't think its a good idea to try dismantling your TPS, if it breaks your car is off the road... :?

Although a lack of wiper tension could be the problem, on a carbon track potentiometer the usual failure mode is the carbon track itself wears out at points where the potentiometer spends a lot of time - for example at closed throttle. In that case tensioning the wiper won't help.
I can get used part pretty easily (if i really need to), so there is no real danger of damaging my TPS and i'm also good at taking things apart :) My idea is to reposition wiper on carbon track (didn't know word for that) as it's usually much wider than wiper itself. I did this some years ago for another car with another problem. And if that makes any difference, it's time to order new replacement part.
Mandrake wrote: Will that ebay seller I linked to not ship to your country ? (Where are you again ?)

If you're really stuck and can't find one for a good price anywhere let me know and I could get another one from the same seller and post it to you if you're willing to pay the extra postage...(I have no idea what the postage would be but its very small and light and would fit in a bubble bag)
I'm from Finland, i'm pretty sure they ship it here too. I know i just should order it, but i have been busy with other things lately and fixing my car has not been those things that get me excited right now :) Anyway, thanks for your offer to help.
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falling-out-with-my-car
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by falling-out-with-my-car »

I wish I had time to wire up spark plugs to amplifiers :roll:
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Mandrake
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by Mandrake »

Stempy wrote:You know, if you feed the LT side of an ignition coil from the speaker output of an amplifier you can make a spark plug attached to the HT side dance to the music.....
I have two spare coil packs, but given the primaries at 0.5 ohms I don't think I'll be connecting them to my amplifier... :twisted:
addo
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Post by addo »

3.5Ω wirewound, in series?
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Mandrake
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Re:

Post by Mandrake »

addo wrote:3.5Ω wirewound, in series?
Well given that my amplifier is over 20 years old and I've had to repair it 3-4 times in the last 5 years to keep it running (I'm not someone who buys and owns new/expensive audio equipment) I don't think I'll be playing the coil and spark plug game with it. ;)

(The attempts to push this thread over the 100 page limit with OT chatter is painfully transparent guys :-D I reckon I can have this car fixed by page 100 otherwise...)
Xantidote
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by Xantidote »

Mandrake wrote:I reckon I can have this car fixed by page 100
Promise?? Certainly hope so, as you deserve it for all the time and effort you've put into it. Perhaps sorting the engine's become a challege you can't give up on
addo
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Post by addo »

Perhaps if not, he should relinquish it to Team WFA for 48 hours.