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UK Car Repair/citroen xysara Picasso 1.6 petrol 8valve cutting out or losing power


QUESTION: I  have a 2005 Citroen picasso 8valve 1.6 petrol engine.It started a year ago on a very hot summers day driving back home some 200km when it just cut out and i had to wait a while before driving everytime. During winter 2012 it didnt cut out. but now in summer  when its hot during the day it will cut out after 10km of driving at a robot or in traffic whilst idling.There is a sort of rich burnt fuelish smell when it cuts out. wait a few seconds i will start it up with no problem. Should i start immediately it will crank fast for a while before firing! If on the highway it will lose power with no effect on the gas pedal and then accelerate after about 4-5 sec with revs picking up and should I change revs to slow down it will lose power again to repeat the same procedure and it just becomes worse or more sensitive to rev fluctuations until then it will just cut out irrespective of rev change! I have had my step up idle sensor replaced , air flow meter in the ecu cleaned, fuel filter changed, proper Bosch spark plugs, oil etc.I have had on diagnostic machines for fault codes , one said i should check my fuel pump, another said i must replace my cracked exhaust manifold and my upstream oxygen sensor/lambda sensor replaced because the sensor is losing voltage when it over fuels and cuts out, another expert says i can replace the above that but it wont solve my problem. At night she's smooth unless i drive fast(+60mph)  for about 15-20min and then she may cut out or lose power but driving normally at night seems fine. I think if she idles until hot she may cut out! Mileage is 126875miles. I have already spent so much and i don't want to pay for all this trial and error- just cant afford it! My fuel consumption is high. Have blackish non oily exhaust pipe even tho i have a catalytic convertor. Engine does not use oil! thanks for your help!

ANSWER: so it runs rich and starts cutting out after 10k. cracked manifold won't cause this.

EGR valve could..

did you get the fault codes when it was scanned? - they're not easy to interpret by the average mechanic, leading to changing the wrong parts repeatedly - if you could get the codes to me I can properly diagnose it.

It could be any of a dozen sensors or a minor mechanical problem with the engine. Codes are paramount.

also, the parts removed so far have value as they're not broken, if you still have them ebay them.

Get back to me with the codes.

What *I'd* do because it just might work:

*chuck in a bottle of fuel system cleaner/redex etc - then drive in 3rd, floor it to accelerate to 5000rpm, let accelerator go completely till engine slows to 2000rpm then floor it again (find a quiet, straightish road, you want about 5 miles to do this), repeat accell/decell 10 times, then drive normally and see if the problem is cured - 50/50 chance :- this can loosen up a sticking egr valve* (they usually stick through lack of use, this sort of driving+fuel cleaner gets the valve scorching hot, opens and coses it violently and burns off tarry oily deposits)

Don't do it if you doubt your ability to control the car under hard acceleration.

Get the codes in any case.

---------- FOLLOW-UP ----------

QUESTION: thanks for coming back to me sooner than expected- much appreciated! I filled a 500ml of fuel system cleaner in the tank and filled the tank with 40litres of unleaded petrol! I was cutting out, at every drop in rev on a reasonably warm day 28 deg celsius as i made my way through the suburb roads to a car spare outlet! I think we are closer to solving or zeroing in on the problem- after i filled up as per instruction on the fuel cleaner label the problem disappeared immediately! I idled for a while at a robot and expected the car to switch off- but it didn't- this relief Lasted until the computer said i have 175km left in the tank and then it showed symptoms of losing revs on the freeway and picking up 5-8sec later without cutting out! i think the the black outline on the exhaust maybe because i hav my foot still depressed on the accelerator when the revs drop. I put in 25 litres of gas again and the problem disappeared again until it reached 2 digital bars on the petrol guage and said 165 km left in the tank! I also took the petrol cap off when it started cutting out thinking that my petrol tank breather maybe blocked!
I trust that this will help define the problem? Thank you

fuel pressure regulator/fuel pump/fuel delivery etc.
so it's gone hundreds of miles on a full tank+fuel cleaner without issue but when there's only about 4 gallons left starts cutting out WHEN theres lots of engine vacuum (idle/decellerating).

I think fuel pump(in-tank pump) is jamming when you idle or decellerate(engine vacuum increases when you close the throttle/decellerate in gear, this vacuum adjusts the fuel pressure regulator to let less fuel past, this closing of the regulator (basicly a valve in-series with the fuel pump) puts strain on the fuel pump and causes a surge or jolt in the fuel line, a worn pump can jam under these conditions), or the fuel pump has an air leak and lets air into the fuel line when the fuel level in the tank no longer fully submerses the pump ;)

it could also be a bad fuel pressure regulator or fuel pressure sensor:  it really would be best to scan it for diagnostic codes- the more I research this engine the more difficult it seems to diagnose from symptoms only, it is imperative to scan it really...

if running diagnostics is absolutely not possible try to have the *fuel pressure* checked(with low fuel and cutting-out apparent*), if the fuel pressure is way out of specification or fluctuating worryingly (surging then waning)  you have found the fault.

But that's all you can test.

Honestly, beyond bashing the EGR valve and testing the fuel pump Diagnostics is the only way to go, there are 2 dozen different faults that can cause this problem.

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Christian Boyce


Extensive knowledge of cars designed between 1900 and 2000. I have an interest in keeping these early cars on the road - I love the classics and want to keep them around. I'M BACK!. A LOT of reasonably classic cars are going TO SCRAP with no good reason. I want to stop that. If it's cool and you're having trouble with it, just ask. Also I'm looking for a job. I can do bodywork too. Not welding yet. Everything else and more though.


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Elec-Installation (bolton college) Digital and analogue Electronics (Bol Col.) Digital Microprocessor Electronics (Bol Col.) - Pc Inst, Diagnosis/Repair NVQ3 Bury College.

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