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Vacuum leak and unstable Fuel pressure.

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As the title suggests..

I set the fuel pressure at 2 bar , using stock injectors on a 2jz.

It some times hold 2 bar but after one WOT run it drops down to 1.2 , 1.5..

Meanwhile during decel the Afrs get pegged at 11.5 and Idle jumps up to 2000 rpm.

I am assuming there is a vacuum leak some where which is causing this behavior.. also

the FPR might be faulty.

Am i going in the right direction ?

Base fuel pressure of 2 bar is quite low and will affect the characterisation of your injectors and atomisation of the fuel itself, I'd try upping it to 3 bar base pressure and see if that helps.

Toyota uses 3 bar base differential pressure

Its not even holding up 2 bar at all.

even then should i try upping it to 3 bar ?

There is clearly something wrong but if it's not set up right at the start you can chase ghost issues all day. Set it up as it should be and take it from there, that way you know it's set up right and the injectors will run a lot happier at 3 bar base. If it can't even manage 3bar then you have a serious supply/control issue, I doubt it'll be coming from a vac leak.

What fuel pressure are you getting on decel when your AFR's go to 11.5?


Set the base pressure to 3 BAR. Took it to a cruise, the needle initially went up and then started dropping coming to a stop it went back up to 2.5 BAR.

The shaft on which the throttle cable is connected also the TP sensor . After giving throttle some times gets stuck , some times at 3K , some times at 2K.

In terms of your fuel pressure, Chris is right - Start with 3 bar differential pressure (set it with your vac line disconnected from the regulator. From here with the vac line reconnected the fuel pressure should increase as you climb into boost and decrease as you drop into vacuum. If it's not doing this then you need to fault find either your fuel pump, the pump wiring, or your regulator. Provided you're using a quality name brand regulator then these are typically pretty reliable.

As far as the throttle goes I'm a little confused? Are you saying the throttle is physically sticking and not closing again correctly? If this is the case then it's a mechanical fault and you need to address this.

Hi andre,

I tried the same as suggested by you [ 3 bar ] but the pressure is not going up and comes down to 2 Bar or 1.8 bar on vacuum. New FPR and new fuel pressure are going to be installed.

The Throttle is physically sticking ! i dont know if this is serviceable or i have to replace the tps assembly.

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