surges and sometimes erratic idle.

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Philip Chidlow
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surges and sometimes erratic idle.

Post by Philip Chidlow »

19 n/a. Lucas pump. Starts fine, runs well generally, doesn't smoke much and is relatively spritely. No unusual sounds and a recent fuel filter change showed no metal bits in the can (pump ok then?). Pump doesn't leak and there's no smell of diesel from anywhere other than the filler neck if I fill it up to over 3/4. Recent oil and filter change. Throttle cable lubricated at engine end and pedal's not cracked/bent (AFAIK).

None of the recent work has cured a slight 'annoyance'. Most of the time - particularly when warmed up - the car runs really well, but I occasionally encounter surges of power when I don't input such a request via the pedal... most odd. What's more I can drive up to a set of lights and the idle rests at 1500 rpm, then, when I pull away, at the next set of lights it'll be 1000 rpm... there's no pattern to this idiosyncrasy.

Then, sometimes I'll encounter a slight 'flat spot' (but fairly rarely).

It's more often than not uneven power delivery (for want of a better description)... It doesn't make the car difficult to drive (although it helps to be aware) and it never fails to go...

Any thoughts? Or is it simply a knackered/sticking throttle cable?...
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Post by Defender110 »

I would suspect a slight airleak in the system anywhere from pre-lift pump back.
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Post by Oilyspanner »

Another vote for an air leak somewhere.
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Philip Chidlow
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Post by Philip Chidlow »

Well, adusting the screw slightly on the throttle lever has cured the idle oddness - except for an instance of 'hunting' yesterday. But there is still the issue of intermittent uneven power delivery. Kermit seems unconvinced it's an air leak, (I did spend some time describing the problem - more thoroughly than here admittedly - with sound effects :lol: :wink: )... I wondered if it could be a pump/injector issue?
• 1992 Citroen BX TZD Turbo Hurricane
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Post by Brian »

Hope you find an air leak, that would be a simple fix.
But, if not:
I had a similar problem on the 17rd Visa with a Lucas pump.
It turned out to be something breaking up inside the pump, bearing cage maybe.
Only found when lifting the lid on the pump to be greeted with metal fillings.
Did not even strip the pump any further.

My solution, Bosch pump, pipes and injectors from a C15 van from a scrappy, that fixed it..

Good Luck
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Philip Chidlow
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Post by Philip Chidlow »

Thanks for the advice everyone, but as often happens I appear to have found the solution through tracing the history of the problem. I traced it back to filling up with diesel from Tescos prior to leaving from the UK for Brussels when temperatures were between minus 5 and minus 9 C. The problem got steadily worse and on one morning (when it was minus 13C) the car wouldn't start. Eventually as the temp rose I was able to start it and it was then garaged. The following morning although the outside temp was very low still, the car started first time...

OK this pointed to diesel turning to gloop in the cold. So I filled up with diesel from a LUK service station outside Brussels, having been reliably informed the diesel was high in winter additives. Sure enough it seemed to help... but the problem of odd, occasional surging and intermittent rough running persisted.

Change the fuel filter. The old one was shot, but nothing too far gone to suggest it was to blame and it now sports one of Purflux's finest.

Still issues. So, convinced it was probably a fuel issue I let the fuel tank run down and put 30 litres of BP's standard diesel in. Slight improvement (yay) but still doing some odd things.

Bought Millers Diesel additive/cetane booster which claims to give the system/injectors a good clean and put a double dose in washed down with 20 litres of BP's top-of-the-range diesel... and...

The problem seems to have largely gone away. A few more doses of good fuel and the Millers medicine should, I hope, see the car back to normal :)
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Post by JayW »

Fuel heater on the back of the block tends to become porous and suck in air with age. I cured the same fault by simply bypassing it. Jobbed.
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Post by Philip Chidlow »

Hi might be worth doing that just in case then?
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Post by JayW »

Well, i've certainly had no recurrence of the problem since. Oh and just in case the vultures are circling, i also had no issues with the fuel gelling including through last winter (down to -15c).

It's very easy to do, just repace the fuel supply hose (10mm) from the metal pipe beneath the drivers footwell straight to the priming bulb (bosch) or filter head (lucas). Then either cut back the old hoses or just tie out of the way.
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