Acceleration Problem

[masg111]

I have a problem with the girlfriends car a 1.1 Saxo (W reg 2000 - Single point fuel injection) which I hope some can answer for me.

The car has had a problem accelerating for quite a while and I have tried to fix it but nothing seems to work. The problem is most evident when under heavy acceleration or the car is going up a hill. If you put the foot to the floor quickly it loses all power and it surges and there is a clicking sound towards the rear of the car ( I though this might be the return of the unburnt fuel back to the petrol tank) but it sounds quite loud for a valve opening. The other issue is when your accelerating moderately it kind of surges, if you reduce the acceleration it goes away. The problem does not appear to be linked to speed of the vehicle or engine temperature and there are no engine management warning lights. Under little or no acceleration on a flat road the problem is hardly there.

So far I have changed the ignition coil and HT leads (recommended from a garage diagnostics) this didn't fix it. I managed to get a fairly cheap throttle body unit so I decided to change that as this is usually a cause I'm told. Fitted that, it seemed to fix to surging at low speeds but not the sudden acceleration, however the problem has come back across the board now.

Apologies for the rambling description but I'm tearing my hear out trying to fix it, its becoming a safety risk (pulling out at junctions with complete loss of power) . Thanks in advance for any help

[babers]

if there is a noise at the back mate it could be the fuel pump. it does sound like a fueling problem check the fuel filter and all fuel line to make sure they are not blocked. hope that helps abit

[Ben_L]

didnt buy dodgy petrol from tesco? lol. have you checked your plugs and stuff?

[masg111]

Thanks for the replies so far.

Plugs look ok, the right colour and not to much soot. The girlfriend has bought petrol from Tesco so this could be the problem but the poor acceleration has been an underlying problem for months, just seems to be getting worse. it could be a lambda sensor issue but it past an MOT about 4 months ago and the problem was evident then (although not as bad).

Do you know if the fuel pump provides a constant pressure to the engine or is it increased during high demand . i.e the car is able to get up to 80+ so there is enough flow but it could be to do with how that flow is regulated. I did change the throttle body in case this was the cause but that hasn't helped. I'll check the fuel filter just in case.

It just feels like on high demand the engine either dumps loads of fuel or air into the chamber and it doesn't combust properly, I may just change the sparks just in case they are faulty.

[babers]

lamba sensor would throw up the engine managment lights. its more then likey be low fuel pressure. when you are flooring it.

[tubbytommy]

i basically had this problem, would kinda back off goin up hill and had foot down. only in the morning when cold tho. had the lamba sensor changed as i had it diagnosed and he said it was that. but so far still happens. i changed the plugs but still does it. let me know if u fix it as its drivin me mad now!

[Jon_Doe]

My sister had this problem in her car (not saxo) and was a fuel pump.

Try that and also fuel filter, that would certainly hold back fuel if a bit blocked. Do the fuel filter first, quite cheap and might solve it- the click though sounds like a a fuel pump - i assume without checking) that there is a fuel pump relay- if you are getting complete cut outs it could be on the way out. (relay getting damaged can be caused by an old pump drawing too much current- if you are near fuel pump does it make a whining sound (louder when on low fuel and once running for a bit) ??

[Barry123]

when was the car last serviced?

[masg111]

The car was last serviced about 6 months ago (5k miles).

I just bought a new fuel filter and if that doesn't fix it I'll look into getting a new pump . I'll post a reply and let you know what happens

thanks for the advice so far

[masg111]

when was the car last serviced?

VTS ? Nope I just got a skoda Octavia 2L TD