had the car stripped to fit new belt etc

everything was cool for a few days and started getting problems

checked timing etc to see if all was good and is in fact the same so no worries there

the problem is that in 1st 2nd and 3rd gear if i use wide open throttle at about 3 to 4000 revs the car starts to buck as if its starving of fuel or its blowing the spark out sort off , a bit like a learner driver with the clutch if u know what i mean

if partial throttle is used to raise revs and boost all is fine until reaching wide open throttle , then the bucking starts but only in 1st 2nd and 3rd , not 4th or 5th ?

car has apexi panel filter , greddy type rs bov vta with spring tightened right up to make sure its not that leaking

other problem i had before is on cruising the car would die unless i stuck the foot down at LOW revs , took spark leads off gave them a clean etc and stripped all pipes and tightened everything up tight and much more , took it out for a run and evrything was fine apart from the problem i have now ? it seems that i have in effect reversed the problem some how ??lol

coil pack is all in one type not individual ( car is v5 sti )
spark plugs maybe
maf ?

dont want to waste too much time hanging around this as it can be a nightmare really ?

no fault codes either

basically bucking on boost at wide open throttle above 3 to 4000 revs ? sometimes lower ?

 

Had a similar problem with my MY94 WRX years ago never ever sussed what it was and sold the car that way as it was already up for sale anyway. I had a funny feeling it was the MAF but would be interesting to see what it is if someone sheds some light on it for you an if it's a common problem.

 

what boost you running mate as it sounds like fuel cut on over boost?

 

id go with cleaning maf with carb cleaner first sounds like a maf problem but do the obviouse first check plugs/connections on sensors etc good visual look around steve

 

It sounds like fuel cut to me. Check boost pipes and the usaul sensors first. You may need to get a live data reading to find out exactly what going on though.

 

its not fuel cut , wish it was = easy fix boost is fine and manifold pressure stays constant when the buckarooing is happening so dont think its down to pipes really .

was told that the obd2 diagnostics wasnt really meant to be used whilst the car is running , i know what u mean by dataloging the car , only prob is i dont think the obd2 tool will work when the cars running , OR SO IM TOLD ???

will the scan tool pickup any fauts that the oem ''check engine'' display wouldnt ?

im hoping its the plugs needing gapped as said it feels like the sparks being blown out as the bucking instantly stops with backing off the throttle but still maintaining acceleration and returns again on wide open throtle in 1st 2nd and 3rd

basically a mid rpm misfire really but feels like at least 2 cylinders misfiring to get that amount of jerking

hit the fuel cut hundreds of times before on older cars and the boost is knowhere near fuel cut material ( standard boost )

 

mind u i have a set of hks f35 spark plugs are they to hot a heat range to use with a full decat , panel filter and type rs bov or are they unsuitable ? i know they are originally made by denso and are iridium ones to hks spec ( f35 superfire HKS )
know where to look really just need to know if any 1 has had a virtualy similar problem as it can be a pain going over sensors , plugs etc to find it being something damn near stupid lol ,

car also has a dawes device so i know its not a cloged solenoid etc

also the car idles lumpy , forgot to say that , the engine bounces if u will as u can feel the car bouncing at the lights and is somewhat a pain in the *** , this is what pushed me towards coils and plugs

no air leaks on idle etc , vaccum gauge spot on

 

also heard limp mode causing bucking before ? maybe sensing knock at wide open throttle ? this would be a dataloging thing though i guess , no pinking sounds under acceleration to back that up either ?

 

had this just last week on a vauxhall i was tasked to fix> no codes or faults stored and could be driven around perfectly normal on various throttle positions except wide open> when i logged it i found that the maf would not read more than around 90grm/sec of air. New maf and all was cured> also had the exact same thing a year or so ago on a golf> Its not just the scoobies that knock mafs out

 

cant hear fuel pump priming when key turned so expecting a weak fuel pump now as its intermittent and runs bad when low on fuel i have also noticed at least under a 1/4 tank ?? dirty sock on end of fuel pump maybe but tried to listen for it this morning and could really if not hardly hear it at all

mafs also a good point but not cheap even second hand if its not that thats the problem and cant borrow one as everyone i know round here's too stuborn to help u out

 

Ive got/had similar issues, albeit, newage.
Changed plugs today for a higher grade ( 6 up to 7) with a closer gap too (0.7mm to 0.6mm) and looking good so far.

PS. Whereabout Scotland you at?

 

edinburgh mate

wasnt the pump anyway , might try and stick the hks plugs in there but reckon the heat range is too high