HELP HELP HELP 2jz-ge misfiring

[2j Sammy]

Hey guys well i will run over the whole scenario so that you can understand the issues i have had and now the issues i have had now.

In the past i have experienced a similar problem and after much fiddling it turned out that it was corroded fuel pump wiring, which got fixed up.

What is almost feels like is a similar sort of thing. It sounds like the fuel pump switch/relay is not receiving the low voltage. Trick is that would be weird for the high voltage to get there with no problems?

Issue: Car is misfiring below 3k revs unless im belting it and when cruising at any revs. This in turn is making it run lean (around 15-18)

Again AFR's are fine when i belt it, running rich as but when 'cruising' it jumps to a misfire and leans right out (due to lack of fuel me thinks)

My thoughts:

- to my knowledge the ecu takes over when in 'cruising' mode and under 3k correct? I think it is an electrical fault because of this.


Things i considered maybe faulty:

- TPS
- MAP sensor
- o2 sensors
- ECU
- Fuel Pump relay
- Fuel pump wiring (have had problems with this in the past)
- Fuel pump
- Coilpacks
- Ignitor
- Fuel filter, however i would of thought if this was up the wall that it would affect fuel supply 100% of the time
- FPR - again if it was this wouldnt it play up all the time? or at minimum random times?

Things that have been checked and are in order:
- Spark plugs
- no evidence of vac leak
- oil
- coolant
- Battery
- New k&n pod filter
- Injectors have been cleaned recently

I think that is most of the info - i have heard you guys are the cluey ones so hopefully you can help me!!!

Thanks in advance

Sammy

[RT40Corona4AGTE]

what is your fuel pressure at idle ?

If its an aftermarket FPR what did you set it to at the beginning? is the value you have now for fuel pressure different to what you set it to then?

have you checked your CAS? is it near any sources of heat?

with respect to the fuel pump voltage thing, if your ecu runs a higher voltage to the fuel pump at higher rpms, then the higher volts would make it past a shitty connection better than what a lower amount of volts would. Hence why it might appear to be fine up the top of the rev range? I am unfamiliar with how the stock ECU operates fuel pump wise or whatever ECU you are running though for that matter.

Most aftermarket ECU's just switch the pump on via relay that I have come across, unless you are using a fuel pump booster circuit or something like that.

Could also be a sticky TPS, as in stuck open and not fully closing when you back off to idle.

See what else you come up with? I am fairly unfamiliar with 2J ECU's though, so I hope someone jumps in here to help you further! Hope this helps!

[madmont]

The 2J ecu usually runs the fuel pump through a fuel pump ecu and switches to a higher voltage at about 4000rpm giving more flow

[2j Sammy]

RT40 Corona - I have not checked my CAS - i will have a peak around it tonight but i dont think there is anything new affecting it

With respect to the fuel pump relay voltage- your guess is as good as mine at this point. I mean in theory your right but yeh everything isnt always reliant on theory haha.

TPS: the car seems to idle ok, i would have thought if it stuck open that the car would idle high/badly?

I have a stock FPR and stock ECU if that helps?

Madmont - yes yes this is what i believe - i thought it switched at around 3500k but anywho close enough. I wonder what voltage it is supposed to be running at when its in 'cruising' mode?

[midnight_purple_GA70]

fuel pump ecu switches between 9v at idle and low loads to 12v under load...

i would do the 12v fuel mod as your tune will be set based on having 12v going to the pump i would assume

[2j Sammy]

after abit of reading the US guys seem to be melting their fuel pumps by doing that 12v mod - not important now i guess as i need to fix the car rather than mod it but still - interesting as a fair few ppl do the mod.

Getting a diagnostic machine thing so will be able to review all sensors and what they are reading when that arrives