car hesitating on acceleration

[pumpx]

hello guys i have a problem with my 2000 mr2.
when i accelerate on low revs it feels like the car is hesitating just when i press down the pedal and then it drives all normal.
and when i release the pedal it feels like it brakes are applied or it brakes to hard on the gears.
but only if i have less than 3500 rpm on the car and the problem is more noticeable when the engine is cold.
if i press the clutch in when decelerating its all normal.
i have tried to clean the maf, throttle body,new exhaust manifold, injector cleaner, new airfilter, new plugs and cleaned the iac sensor.
is there anyone who might know what it could be?

[stargazer30]

Try driving it with the MAF unplugged. If it cures it your MAF maybe knackered.

[pumpx]

i have bought and fitted a new maf didnt help.
i suspect it maybe could be a vacuum leak?
does anyone know a good way to find out if i have one and how to locate it?

[pumpx]

tried to test for vacuum leak with a box of carburetor cleaner but didnt find anything.
could a dirty fuel filter cause the problem since the problem disappear when i get on to higher revs and speeds thus the fuel pressure gets higher and the problem get less noticeable?

[pumpx]

nobody knows what it could be?

[Joesson]

How about resetting the ecu, disconnect battery for 30 minutes.
It won't hurt anything and may help the situation.

[normanh]

Have you got any fault codes? Does the engine management light come on when you turn the key, if no light comes on I suspect you have a live code error and someones taken the light out to hide the fault! You need to get a code reader plugged in rapid if its a uk spec car and check if there are any!

Norman

[pumpx]

i have reseted the ecu every time i have done something to the car does not help problem still there.
no fault codes, check engine light is fully functional and had a code reader plugged in found nothing.
thats why i really struggle to find out whats wrong.
tried to plugg out the maf as stargazer30 mentioned just to be sure and the car went crazy as i expected since the ecu doesnt get the air mass data so not a good way to test the maf thats for sure.
its an Norwegian car since i live in norway

[mrzwei]

This feels like a 'breathing' problem. You seem to have covered most of the stuff on the inlet side.
If you haven't already removed them, check that the pre-cats are still intact.

EDIT: You replaced the manifold, so were the precats ok on the old one?

[spit]

Just a thought: Hesitating initial acceleration coupled with the 'early' fuel cut that you're get when lifting off in gear could be a dirty contact track on the throttle position sensor? When they fail they tend to fail towards the 'throttle closed' position because thats where the dirt gets swept back to.

[pumpx]

precat were ok.
i will try to check out the tps.
is it enough to clean it with carburetor cleaner or do it need to be replaced?

[pumpx]

but shouldnt there be uneven idle when its something wrong with the tps.
the car idles normaly

[pumpx]

took of the tps sensor it was pretty clean but cleaned it and the contact anyway didnt help.
so thats not the problem obviously :/

[redarrow]

Clean the ivac.
Clean the maf.
Clean air filer.

Look for any holes in the pipes.

Cheek pipe to the side insert for holes.

If not that then.

Goto a garage and clean the petrol filter only
Let a garage do it,  a pro it very dangerous.

Only my opinion read on here.....

Regards john.

[pumpx]

if you read my first post i have already cleaned and checked all that you mention didnt help.
im going to change the fuel filter my self.
you dont have to be a pro to change the fuel filter on this car unless your an idiot.
you just have to use common sense when doing it  s:) s:)

[mrzwei]

I'm going to change the fuel filter my self.

There is a 'how to' on here if you need it.

 l viewtopic.php?f=47&t=46032 l

[pumpx]

thanks  s:) s:)  i will take a look at it just to be sure

[redarrow]

If the petroll filter has been picking up old
Petroll from the bottom of the tank then bits
Might be blocking the petroll from flowing thru
The system.

To change the petroll filter might not be hard to
Do, but a dangerous part for a amature or non machanical
Person to tackle, no one a idiot even if there not
A Mechanic  minded , please be nice where nice to you.

Me advising you that removing a petroll filter
Is dangrous is mentioned becouse i dont
Want no one just go and do it and get hurt.

Regards john

[pumpx]

i understand that you want to warn people since it involve handling petrol.
but i have changed the fuel pump on a car before and that was much more of a pita since it was mounted under the tank.
so this is just a piece of cake compared to that one  s;) s;)
and im not trying to be sassy or something im just saying its not to hard to do and if you just use common sense, read on how to do it and clean up properly after you are finished there is no real danger unless you begin to modify something that shouldnt be modified.
so im sorry if you misunderstood my intentions on my comment  s:) s:)

[Wabbitkilla]

Will be interesting to hear the results.
I'm not convinced it's fuel filter related ... but you know, it's not impossible.
Reading through the thread it seems you've covered everything I can think of too.
Apart from maybe cam or crank position sensors ... which again are pretty reliable on these cars.

[pumpx]

i interested in the outcome too since i dont know whats left the could give the symptoms i have on the car.
if its not that i just have to bit the dust and take it to toyota an get them to look at it.
regardless of how expensive it is to get them to look at it in this tax country called Norway :/

[mrzwei]

tried to plugg out the maf as stargazer30 mentioned just to be sure and the car went crazy as i expected since the ecu doesnt get the air mass data so not a good way to test the maf thats for sure.

Not sure if this is of any use but just read a diagnostic bit in Car Mechanics mag. If you disconnect the MAF then the ECU should go to its default values. So, if it drives better then the MAF is at fault and vice versa. So it should be a good way to test the MAF because the ECU is getting good enough air mass data.

[pumpx]

hmm.. are you sure about this.
i tried to disconnect the maf on my previous mr2 and it went bananas like this did when i tried it.
as soon as you get a little high rpm it begins to heistate and becomes all jumpy.
i dont think it was anything wrong with my previous mr2 as it acted all normal so.
but i dont know you could be right didnt help on this car anyway

[Wabbitkilla]

No, from my understanding and experience it may tick over and idle without maf but it won't drive. The ecu needs the air flow and temperature fir referencing the fuelling map.

[mrzwei]

No, from my understanding and experience it may tick over and idle without maf but it won't drive. The ecu needs the air flow and temperature fir referencing the fuelling map.

Yeah, that would make more sense. On re-reading the article they were referring to a diesel   s:oops: :oops: s:oops: