Crazy flatspot until around 3500rpm?? making 20kw until then please help

[DoriftoMagic]

so ive a smallport 4age, standard except extractors n a pod. i know the TPS isnt working and i havnt yet looked into what the problem is there but im pretty sure thats not what is giving me a massive flat spot. AFR is lean as fuck until around 3500 so thats why it only makes 20 odd kw until then but ive no idea what may be causing it or where to start looking.

anybody had this problem??
is it a common issue a fault??
is it something simple that im overlooking??

your help will be much appreciated.

[ke_70]

cheaked timing?

[H8CHIR6KU]

if you know the tps isnt working i would be starting there.

if the tps is not reading where the throttle is correctly your never going to get proper air fuel ratios

[DoriftoMagic]

the tps only really makes a big difference in air/fuel when your off the throttle, the only drama its causing me is there is no fuel cut. i have checked timing and the dizzy is fully advanced to get it to around 8deg btdc, but its almost halfway between where it needs to be and being a tooth out. if that makes sense.
im thinking this may be beacuse someone in the past has shaved the head/put in a thinner head gasket which shortens the distance between cam gears and crank.

any thoughts??

[wntdae86]

check timing

i did my timing today and had a flat spot around 3000 rpm after i put 1 at tdc and moved the dizzy to suit so the rotor button is at 1 on the cap and all is good again .... also tps has to work or your wasting time

[DoriftoMagic]

so does that mean your running your timing at tdc?

annnd anyone have a smallport tps for sale? haha

[wntdae86]

5deg b4 tdc

[DoriftoMagic]

yeh thats what mines running at now too.

k, so general concensus is....new tps - take it from there.

thanks guys

[ke70dave]

if you unplug the TPS it will run "fine"

the only thing i noticed when i unplugged my TPS was that it took a while for the revs to drop down if you free reved it.

if the TPS is stuffed and its plugged in it will cuase all sorts of dramas. mine refused to idle and it was running VERY rich with bad misfires when it had a stuffed TPS.

do a system diagnostic too, that will help find the problem.

[DoriftoMagic]

system diagnostics would be grand if i had the fuckin diagnostics plugs in the loom -__- i wish

yeh, as far as im aware the tps controls fuel cut when off throttle and i think it contributes to idle mixtures. thats why it seems to be running rich and fouls plugs. under load its not as big iof an issue.

as for unpluggin it instead of just leaving ill give it a shot, a quick fix for now.

thanks everyone, helping alot :thumbup:

[Chrisso]

The stock ECU should use TPS input for acceleration enrichment and deceleration fuel cut. Aftermarket computers may also use TPS input for general fuelling tables instead of MAP input, or in conjunction with MAP input.

[DoriftoMagic]

BANG
chrisso has hit the nail on the head. i new it controlled fuel cut but the enrichment i wasnt sure about, i got a few different answer from 'specialists'. that would be why its so lean

thanks guys, just concreted my theory. now i know i wont be spendin money n gettin no where.
:)