Slight Power Loss From Time To Time

[petrolhead]

sometimes the power is not as good as normal not a good kick at 3000rpm can be bad for a week or so then back to 100 % can reset the ecu and that helps the air flow meter is clean may be vvti unit or oxygen sensor or ecu problem??? just had the crank sensor fitted recall going 100% at the moment . anyone got the same fault????????????

[Corolla_liftback]

i have a similar problem which i cant understand, i sometimes feel the power dropped off when the car is floored once it goes over 3000rpm-4000 u can feel the drop in power and my foot is still flatand then it might pick up again later on in the rev range. When this happens the engine also gets a lot noisier and sounds very different. It is quite rare that this happens but i cant understand what it is? Il be servicing it next week so see if that sorts the problem out.

[Chosun Wan]

Could it be something like the outside air temperature (ie - on cold days the air is more dense and can have a nominal impact on how a car feels)?

[seveer unaek]

I'll start with possible solutions beginning with the easiest...

Dirty fuel. (poor quality supermarket fuel)

Fuel pump malfunctioning

(basically, fuel starvation)

Dirty lambda sensors (thinks air is too clean/dirty and thus alters the air/fuel mixture to the wrong level)

Spark plugs need changing (clogged up due to deposits running rich... also related to lambdas, or the gap has altered with age etc)

VVTi Controller (unlikely)

I'd say to fill it with a bit of optimax and a fuel cleaner first, reset ecu and take it for a damned good thrashing (amazing how well the Yaris responds to this) I mean a good hour or so, not a run round the block. Then check the spark plugs, if it still does it, then get it checked.

[petrolhead]

i should had said most of the time the cars ok and then for 2 to 3 day the car goes like hell alot better pulling at around 3000rpm and then the next day back to normal . the car was great monday tuesday but coming home today back to just ok. reset ecu and swapped air flow meter with my spare one still just ok may it could be an oxygen senser upper or lower?

[forde]

cant believe noone has mentioned fuel filter yet.

you ever had a new fuel filter? doubt it...

[MR2GTPOWER]

I once heard that the vvti unit is very similar to the vtech, Earpl told me he often redline his car when its old. thus vtec not kicking in. Maybe this is what it is?