[Engine] Spluttering below 2500 rpm

[Softweigh]

Hi Guys

I have a weird issue that only seems to happen after the engine warms up.  Idle is normal when cold but gets a little rough once warm (temp is normal though)  When I pull off from traffic lights the van splutters and struggles to pick up revs until it gets up to 2500 rpm  after that it's fine.  On the freeway as long as the RPM is over 2500 it runs as smooth as silk ..the issue only seems to be from 1000 to 2500      

I have put in new plugs and also found the throttle body was quite dirty so sprayed some throttle body and decarb cleaner as per instructions but neither seemed to help the low rpm issue.     Anyone have any bright ideas ???

[oilyrag]

If there is a fuel filter fitted it would be worth changing it - fuel demand is high when accelerating. What did the old plugs look like, or the new ones after 20 miles. If whitish it would suggest weak mixture, dark a rich one. Presumably the air cleaner has been changed, or at least removed for any test drive. There is probably a sensor that detects air flow in the throttle body and this may become contaminated with oil from the engine breather - easy enough to get to and clean.
Other low cost fixes would include injector cleaner,

[Softweigh]

Thanks Oilyrag

No the air filter hasn't been changed as our supplier had none that fitted so leaving it out and seeing what happens on a test drive is an excellent idea until I can get one. I changed the plugs about 3 weeks ago to try and sort the issue but haven't checked them again. I have also done an injector clean a few weeks ago (the one you add to a full tank of fuel) OK I searched in vain for a fuel filter but there does seem to be one coming directly out of the tank ..is it normal to have a filter under the vehicle as I can find nothing else on the fuel line. When I did the throttle body clean (it was black inside) and had to run the motor at 2500 rpm to do the clean. Would that also clean the sensor or would that need a manual clean .. I'm tending to suspect the air filter (or sensor) now as it's not been changed for 2 years!!! Great advice thank you

[oilyrag]

That's a fair old time for an air cleaner - I get creatures nesting and leaving seeds in mine.  Not sure which model you have, but follow the fuel line from tank to engine to look for one, if there's one at all.  Mentioned in manual as close to fuel tank and a caution that it may be pressurised. Can be depressuried by releasing the valve cap like fitting at the end of the fuel rail, which will squirt some fuel. 
To repressurise, switch on and depress the throttle for a second or two and you should briefly hear the fuel pump run as the pressure is restored.

[Sol]

I'd be blaming the MAF sensor. Try unplugging it and see how it runs. Not reading properly below 2500, not unknown.

[saskak]

I think the OP was talking about the 1.6 petrol version. "Plugs" are probably spark plugs and the throttle body cleaning is more specific to the petrol than the diesel version. The throttle body will be a b it black if it has never been cleaned and the car has a bit of mileage on it.
Most of the 1.6 petrol versions do not have a fuel filter, but some might do and it is close to the fuel tank. It could be the air filter, but also the injectors. They are rather cheap, ~£28 for original bosch injectors. Might be worth checking the fuel flow and potentially replace the injectors.

[Softweigh]

Thanks Guys ..all appreciated .. It's actually the 1.4 Petrol motor .. What is really weird is that this doesn't happen on short runs ..It only starts to play up after I have been on at least a 30 min run at say 100kmh and then when I turn off and slow down and stop at traffic lights ..only then it will start to act up ...on short runs, even up to running temperature it behaves perfectly Where exactly is the wiring for the MAF sensor ???

[Sol]

It should be on the intake tube somewhere - not familiar with the 1.6 petrol however.

[Softweigh]

It should be on the intake tube somewhere - not familiar with the 1.6 petrol however.

Thanks .. I have my plastic hose coming from the air filter housing and that terminates with a hose clamp onto what I thought was the throttle body as there is a butterfly right in the front of the aluminium housing ... There is a multiplug on that housing so would that be the cables doing to the sensor???  Mine is a 1.4 M59 petrol

[Sol]

Could well be, others with petrol versions may know if it is integrated into the TB. On other makes, it isn't but could be on yours. Makes sense to be in front of the butterfly to be fair. If you can look into that bit, there should be a plastic projection from the side into the centre of the bore with a small bead of what looks like glass or resin on two wires, the plug should have up to 4 wires. May be called a MAP sensor on the petrol version. (MAP is pressure and MAF airflow of course, but on some petrol's they use the negative MAP value to calculate airflow or mass)

Unfortunately I know way more about the HDi than the petrol Citroen motors, so hopefully I am not talking bollox regarding your engine (it has been known to happen)