an odd problem somedays no problem and other days I have this problem when warming up if I stop say at a road junction and press the go pedal the car stats to move but very slowly with the pedal pressed right down then all of a sudden it pick up and goes, I am thinking it could be the egr
so .. egr unit in place ???
( thought that maybe you'd get rid of it and fit a 'delete' unit )
i've no first hand experience of egr faults .. got rid of it ages ago .. but ..
it would not surprise me if what you describe is caused by a sticking egr unit
so worth checking its' state maybe
anyhow ..
I have this problem when warming up
so .. it happens only on warm up ?
once cozy .. it takes off fine with pedal pressed right down .. from a stop .. or near-stop ??
maf sensor is new ( stated above in posts )
well .. how old is the air-filter ?? ..
and the turbo solenoid filter ?
every mod i've done to my td4 engine .. has had one aim
to improve engine response from low rpm ..
one thing for certain .. by design .. or result thereof ..
it will never achieve "immediate reaction" to the go pedal at the lower rpm range
there's always .. maybe a 'second' or under .. of hesitation ..
' too much ' and / or ' too fast ' application of the go-pedal just exacerbates the 'hesitation'
the first thing i'd consider.. IF the maf sensor is ok .. would be the state of the air-filter .. as ..
a partially clogged air-filter will inhibit the acceleration of air flow across the maf sensor ..
the result is some 'hesitation' until the air mass overcomes the partial restriction
( low rpm = slow air movement thru the a.intake
( higher rpm with lite go-pedal = not much extra air movement 'cause not much fuel
( and not much exhaust gas to get the turbo 'working' ..
( with the manual g.box that's like .. going thru 1st and 2nd gears
( 3rd gear comes along .. engine needs more fuel to accelerate under load
( turbo now working .. driver floors the go pedal .. should have almost instant response from engine
turbo solenoid filter ..
if it's air flow is inhibited .. then i would think the turbo-vane actuating system would be slower to respond
( i imagine 'humidity' would play a part in either 'air-filter' )
have learnt that either filter can inhibit engine response from the lower rpm range to some extent
that .. plus high humidity .. and high air-intake temps ..
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fuel system :
a.f.a.i.k. a naff injector can show symptoms over a particular temp. range
and be ok otherwise ..
a fuel rail sensor plug might misbehave while the engine is still relatively cold
i.e. less-than-perfect contact between plug pins ..
maybe a lp.fuel pump and \ or filter might cause the 'hesitation' ( as in .. i don't know )
( a duff maf sensor Certainly will )
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either way .. with foot-to-floor go pedal movement ..
if all fuel and air requirements are not met ..
the ecu will not grant extra fuel permission until they are met
result = hesitation ..
if it's something simple .. like a partially clogged air-filter ..
then applying a lite go pedal touch initially .. for about a second or less
( one can feel / hear .. sense .. the change in engine note )
then .. if needed .. boot the pedal toward the floor ..
that works faster than an immediate go-pedal 'boot-in-floor-direction'
.. a hefty fuel Demand ( sudden foot-to-floor action by driver )
coupled with inadequate fuel / air conditions ..
also might waste more time due to ecu processor calculations going on ..
( just speculating )
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i suppose some form of hesitation could be caused by the map sensor as well
i've a separate boost control module that remaps the boost signal to the ecu
and by setting the module so that it reacts at the lower rpm range ..
i get a much quicker get-away-from-junction .. stop lights .. etc etc
can change up quicker .. no need to rev engine much ..
and get a faster engine reaction to quick movement of the go-pedal
( that module plugs in to the map sensor harness ..
( hence me thinking that the map sensor could / might .. cause a 'hesitation' issue
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i've only had 2 engine parts go wrong
the lp.fuel pump .. and a maf sensor ..
( so no first hand experience with other bits going wrong .. and what the symptoms be )
the lp. fuel pump only effected higher rpm under-load performance
and the faulty maf sensor caused massive hesitation if the go-pedal were
pushed too far .. too quickly .. when moving off from a standing start ..
or near-full-stop move off ..
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as for including an auto gearbox .. with it's own computer ecu thing
and how that ties in to driver demands on the go-pedal ..
i.e. how .. or what data .. the engine ecu and gear box computer communicate to each other
don't know IF the gearbox workings would cause an engine hesitation
when the go-pedal is floored ..
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