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

[addo]

I can't comment on longevity, but the dimensions tally and their construction media is correct. To recreate the "bum" of yours would take a proper exhaust centre's skills - not those you normally find in a quick turnaround shop. Doesn't mean it will be dear, just that it requires someone who can visualise the end product and know how to get there.

[Mandrake]

So I've decided that as well as the spark plug leads being dodgy, its high time I replaced the TPS.

Even when the engine has been otherwise performing perfectly with the swapped ECU and temporarily taped up spark plug leads, one problem has stubbornly persisted for months and has not responded to anything I've done - a big flat spot/hesitation just above idle.

The symptom is that the car will be idling perfectly, but if I tap the throttle just slightly with my foot it will stumble/hesitate and in fact nearly stall, with the indicated rpm dropping way down before it recovers.

It doesn't seem to exhibit this for the first 30 seconds or so after a cold start while the cold start enrichment is still active, but it does it at any other time whether partially or fully warmed up.

While driving its noticeable as a stumble / momentary cut out when accelerating from stationary, and it's sometimes noticeable in 2nd gear on take up from coasting.

If I hold the throttle very slightly above idle the rpm will drop and then start oscillating up and down. From all these symptoms I think I have a TPS with a dead spot in it where the wiper is loosing contact just above the idle position.

A genuine Bosch sensor seems to go for an eye watering £92. On eBay the after market TPS's seem to be around £37 and £14. Possibly against my better judgement I ordered one of the £14 ones on the basis that if it doesn't work out I can always refit the original...

Well its arrived, and I'm a bit confused, because it clearly says Bosch, the correct Bosch part number, made in Germany, and looks genuine OEM to me:



So I'm curious whether this is the genuine Bosch item at a fire sale price, or whether its a counterfeit or knock off of some kind ? It came in an intermotor box with a different part number, but from past experience with eBay sellers the box it comes in doesn't necessarily mean anything:



Anyone have any thoughts ? It looks and measures fine so I will fit it, although I'm going to have to take the manifold out to do so as the bottom bolt is seized with very little room to access it thanks to the LHM tank...so I will do it when I swap the plug leads over.

[lexi]

You just may have NOS item there and paid about what these things are worth without Stealer mark up

[Hell Razor5543]

A very long time back I recall a news item about a company who was licensed to make BMW injector pumps. If the pump they made was sold in a BMW box it went for £1,600, while one in their own packaging was sold for either £700 or £900 (I cannot remember which). Either way, one hell of a mark-up.

[Mandrake]

You just may have NOS item there and paid about what these things are worth without Stealer mark up

I think you might be right that its NOS from a warehouse somewhere, and probably genuine OEM, as it would be illegal for a pattern part to be branded Bosch, surely ? I didn't even check the stealer price for it, it was £92 at places like mister-auto who usually have pretty sharp pricing on genuine items.

As you say £14 is all its worth in real world terms, after all its only a wire wound potentiometer in a custom shaped plastic case! No excuse for £37 let alone £92...

[Stempy]

Don't think it's wire wound, it's carbon track.

[Mandrake]

Don't think it's wire wound, it's carbon track.

Are you sure ? Turning the new one certainly feels slightly detented like a wire wound pot, not smooth like you'd expect a carbon track to be.

On the other hand its about 2k7 which is fairly high for a wire wound pot of that size so you could well be right.

[Stempy]

Yes, when I replaced mine I 'dismantled' the old one to see if there was any wear in the track but it looked absolutely fine.

[Mandrake]

Yes, when I replaced mine I 'dismantled' the old one to see if there was any wear in the track but it looked absolutely fine.

Fair enough. What prompted you to replace it out of interest, and did it make any difference to anything ?

[Stempy]

I changed it because the Xantia had passed 100k miles and having had previous experience of worn TPS's in the past on other vehicles I considered it a bit of preventative maintenance. Made sod all difference to performance though, but it was running perfectly well anyway.

Have you tried using these plugs?

http://www.gsfcarparts.com/905aa3600" onclick="window.open(this.href);return false;

[RichardW]

Service.citroen:

Part Number Description Quantity Price excl. VAT Price incl. VAT
000016288V POTENTIOMETER 146.46 GBP 175.75 GBP

[Mandrake]

Service.citroen:

Part Number Description Quantity Price excl. VAT Price incl. VAT
000016288V POTENTIOMETER 146.46 GBP 175.75 GBP

Thanks Richard, I needed a good hearty laugh...

So mister-auto's £92 was a bargain compared to the stealers price...

Surely there is some sort of EU regulation that would prevent such blatant gouging on spare parts by car manufacturers ???! Especially when its a Bosch part that is almost certainly used by many different cars and engines, not just Xantia and 406 V6's...

To sell a £14 part for £175 seems unbelievable, you could argue a strong case that they are purposely trying to obsolete old cars by way of pricing the parts out of the stratosphere so that they can con you into buying the newest models...

[Mandrake]

I changed it because the Xantia had passed 100k miles and having had previous experience of worn TPS's in the past on other vehicles I considered it a bit of preventative maintenance. Made sod all difference to performance though, but it was running perfectly well anyway.

I see. What sort of symptoms have you seen on other cars that did have faulty TPS's ?

Have you tried using these plugs?

http://www.gsfcarparts.com/905aa3600" onclick="window.open(this.href);return false;

Nope, haven't tried any like those.

When I bought the car it had single electrode NGK BKR6EIX in it, they seemed ok for many months but did start to foul a bit, when I started having all the misfiring problems late last year I replaced them with some Bosch FR7DC+, also single electrode, they were hopeless - in under 1000 miles they fouled badly especially the back row to the point where they were tracking on the insulator and causing additional misfiring.

I then replaced them with dual electrode Bosch FR8KDC and after over 1000 miles took them out to have a look - absolutely perfect condition with clean white insulators even though the car had been intermittently misfiring while they were in.

FR8KDC are the factory specified types and a heat range hotter than both the FR7DC+ and BKR6EIX, so I think the previous plugs were just running too cold given the predominately short trips I make. It's hard to be scientific about it but it does seem like the engine runs better on the dual side electrode plugs as well, even before any fouling occurs.

I'm happy that the plugs I have in there now are right for the job and aren't causing any misfires or poor performance. When I change the leads I will pop them out to inspect them for fouling, but intend to re-fit them unless I find something wrong with them.

[Stempy]

I see. What sort of symptoms have you seen on other cars that did have faulty TPS's ?

Hesitation and stuttering.

I've used the Bosch Super Four plugs in numerous vehicles and every time the fuel economy improves. Had them in the Xantia and currently in the C5, the Honda and my recently departed Kangoo. Will be fitting a set to my new(er) replacement Kangoo too.

[Mandrake]

I see. What sort of symptoms have you seen on other cars that did have faulty TPS's ?

Hesitation and stuttering.

Sounds familiar.... hopefully replacing it has some effect.

I wish I could change the TPS by itself first so I can isolate any changes due to the TPS from those due to changing the plug leads...but I just can't get it out with the manifold and LHM tank in place as the bottom screw is barely accessible and is tight all the way out as if its full of thread lock. (the top screw is fine) I got it a couple of turns undone with a tiny right angle ratchet before the head started to strip so I gave up and tightened it back up again. I'm probably going to have to hacksaw a slot in the head to get it out now, when I have easy access with the manifold out.

I've used the Bosch Super Four plugs in numerous vehicles and every time the fuel economy improves. Had them in the Xantia and currently in the C5, the Honda and my recently departed Kangoo. Will be fitting a set to my new(er) replacement Kangoo too.

After changing the plugs twice in a year I don't really want to change them a third time! But I'll keep them in mind for the future.