Back Firing/sputtering. Slugish Gtr :(

[shaunpierre]

ok this problem has plagued me for past couple months and iv tried every thing to fix it.

car is ok and drivable up until around 3000rmp then it often misses and back fires and jerks. i have no acceleration.

some times im lucky and get a smooth rev to about 5 then it, with out fail sounds like im on the limiter papapapapapap lol also back fires often when changin gears

so its just runnin rough as shit

i have so far

-replaced afm with un opened afms

-re soldered both afms

-fuel filter

-coil packs ( 33gtr )

-new bosch copper spark plugs

-cleaned afms

-checked for exhaust leaks

-reset ecu

car is stock with 150000 kms, cat back concept exhaust

iv read a thread with a similar problem. but my coil packs dont have cracks.. iv also been told could be possible its my afms again.... or fuel pressure regulator

any sugestions at all or ideas please pm me or reply thanks guys

[JnJ]

checked injectors and fuel pump?

[GTR_JOEY]

does it happen more once its warmed up, or is does it happen straight from start up?

have u checked your ignitor?

checked fuel rail pressure?

[DVS JEZ]

Check ALL cooler pipes for splits and good connections

[mad082]

+1 for cooler pipes if you have ruled out everything else. also might be worth putting it on a dyno to see what the AFRs are doing when it happens. if they richen up when it does it then you know it's a leak

[BOOZTJUNKEY]

Sounds like a boost leak or fuel delivery issue

Check ur accordion hoses ( rubber intakes ) they maybe sucking shut and chokeing it out . They should not be able to suck shut

Also cooler piping and and vacuum lines for splits or poor connections

And check fuel pressure at the rail And timing of the engine

And post results when done pls

[shaunpierre]

ok i resert ecu again.

i checked fuel pump and its working and winding and pumpin fine.

checked all cooler pipin. some wernt tight as some ppl would like but they wernt leakin or loose.

all vacum lines look fine... i got a ke and i re done WHOLE vacum line network lol night mare

not sure how to check pressure and timing...will do some reasearch and get back asap

i know is somthing so simple... would it have any thing to do with o2 sensors prehaps

thanks guys

[shaunpierre]

k talked to few peeps and afms must be prob....

cant fix it this week got a defect on my daily..... so got to work hard to get it back to scratch. such a joke

thanks for help guys will up date asap

[shaunpierre]

OK fixed my daily... finaly

got done for to stif, wheels to wide, jdm head lights, dash and front lip. but thats another story lol

been driving gtr alot and its been gettin better i checked all piping and vac houses again but nothin seems sus.

it happens when ambient temp is over 25 of below 18 around that... so it mush be afm. or the plugs and wires that make the connection to the afm...

thanks again for all the help guys, ill change the cables and update soon