C20let misfire under hard load

[Chevette madman]

Right not a nova but mk2 Astra gte 16v with c20let just fitted
engine was fully rebuilt and runs spot on when driving steady if I slam the pedal down it will pop and bang at any rpm only when hard throttle is applied sometimes I can nurse the pedal and get rpm up to about 4K before it starts it like your turning ignition on and of and others it just pops misfires boost when it does to around 9 10 psi Amal valve is fitted etc
spec is completely standard engine
Standard ecu
massive front mount and 2.25 pipe work
volvo t3 actuator fitted
everything else is standard

NOW IF I UNPLUG AFM CAR TICKS OF HIGH AND LUMPY BUT BOOST RUNS FINE UNDER FULL THROTTLE ???

i have changed

new fm coolant temp sensor
new cap new rotar
new leads
new bkR7eix plugs tryed 2 sets at 40 quid a go !
new fuel pump relay
new cool and amp
new afm

all parts fitted were brand new not second hand losing faith in this now I've spent so much
eml is wired up and flashes no codes ???
Odd how it boost fine with afm unplugged


any ideas ? I will pay for the right person to sort it
cheers in advance

[Will F]

What plug gap are you running?

[Chevette madman]

0.75 I have tryed 0.6 also also tryed standard let plugs no different like I say unplug afm it flys which makes me think it Carnt be spark related ? I may be wrong it's my first let I am fully qualified mechanic done many crazy conversions Volvo t5 in manta etc but this I Carnt just put my finger on cheers

[Plug]

What are you boosting at? Is it not over boosting

[torquey]

Checked wiring to afm?

[Chevette madman]

It's boosting to 10 psi then settles on 9psi when it does boost !
checked wiring mate all way to ecu plug

[meritlover]

check the vac hose to your FPR.

[Will F]

Plugs should be RS Turbo NGK (cant remember the p/no) gapped at .6mm

I am also assuming you've tried another AFM? (notorious weak spot)

[Southie]

[QUOTE=Will F;2286616]Plugs should be RS Turbo NGK (cant remember the p/no) gapped at .6mm
Plugs are NGK bcr9es.

[Chevette madman]

Still the same tryed ts turbo plugs on Sunday no difference tryed a new non gen afm ran like shit so I guess I need to get a Bosch one to try does any one on here live local to Stoke on Trent Buxton with a good working afm I could borrow for 5 mins to try cheers if u unplug it its spot on boost fine ?

[Chevette madman]

I will add now I've drove it abut more it seems to do it around 4000rpm when boost it just getting up to 10psi I have tryed joining pipes on Amal and just does the same but not as harsh I've tryed adjusting actuator up and down it violent when it happens it try's to throw u threw the window !!! I've held the fuel pump relay and it does click when it happens I am lost with this one any one point me in direction to a good rolling road that mite be able to find my problem

[Chevette madman]

Relay doesn't click bloody phone *

[Will F]

So is it boost cut or a misfire?

Have you got an EML?

[Chevette madman]

Just started car from cold if I Rev it to around 4000rpm it will misfire will being reved but when drivin its a violent cut eml is wired in and works shows 12 and 31 not runing and just 12 when runing if I unplug afm light comes on and I get code 73 afm so yh its all wired in also have had works solus pro onit with 10 pin adapter and shows no codes I have tryed it with pipe straight from cold side of turbo to actuator I only get 6 psi but it still the same also changed leads and cap again today !!! Another 50 quid I should have burnt lol

[Will F]

So it does it even when the engine isn't under load??

Its def not boost cut then and unlikely to be plug-related - if its missing even when you rev it up - it has to be fuel or lack of related... Or ignition I guess.

Plug colour? All the same 'flesh' colour?

[Chevette madman]

Well 500 quid later I've fixed it and didn't need to buy any of the new parts :-(

DONT NOT USE ROOSE MOTORSPORT AFM TO TURBO HOSE
i swaped the hose for a standard item and the car runs spot on !! At last
wouldn't have thought a brand new hose would have done this I don't think I have seen any one ever nock Roose hoses but I have to say thanks to all and will for your help :-)

ps I have brand new non fm afm I ordered last week which came today which I don't need in box new 60 quid if any body wants