Lexus IS Forum banner
1 - 11 of 11 Posts

·
Registered
Joined
·
16 Posts
Discussion Starter · #1 ·
I have a na-t ggp 03 is300 that i FINALLY was able to get running. Yes, i am running a standalone, i am running a ms3x (Megasquirt 3 expansion pack) It was running fine for maybe about 3 weeks prior before running into this problem. I was driving to my buddies house about 30-45 mins away give or take and randomly the afr to my car went from 13-14 to 16-18 out of the random. Now, since i got my car back, i noticed i had alot of exhaust fumes coming into the cabin, i figured it was me burning off the oil on the new parts and didnt think about it as it wasnt AS bad but this time it was BAD, my eyes were literally BLEEDING even with all my windows down. I also noticed my car would take absurdly long to start up and my aeromotive was reading 20psi no matter what i did to adjust it.

Now im thinking this:

Before i got the car tuned, the tuner said i had a valve cover gasket leak as my cylinder 1 spark plug was SOAKED in oil whereas the other spark plugs were fine. Maybe its a misfire? Changing it anyway this week.

Maybe my fuel pump is weak? Im running a walbro 255 and didnt expect it to die on me that quick, was thinking about switching to a hellcat pump.

Maybe its my o2 sensor under the passenger seat? its the ONLY sensor that isnt plugged in. Didnt think i needed to since im running a standalone but it is the only code i have (Besides some tps issues, ill get to that next, coolant sensor issues and power steering issues)

My tps sensor is bad and has a big hesitation and dosnt know where to idle at so when i get to a stop sign and i go in nuetral i have to rev it before going to a stop otherwise itll shut off. I feel like this adds to some issues idk. Figured id mention it, swapping a working throttle body in this week as well as a xcessive throttle lock.

Not sure why this is happening all of a sudden but i guess this is what i signed up for haha, any help is appreciated! I am 100% changing the valve cover gasket and my throttle body this week but any other advice on what i should do next is much obliged!
 

·
Registered
Joined
·
433 Posts
Loss of fuel pressure is likely due to something wrong in the fuel pump hanger. Could be that the wrong hose was used for the fuel return routing and it's not safe for submersion so it rotted from the outside in. Seen it happen several times before. It's very easy to remove the pump hanger to inspect it. I'd start there.
 
  • Like
Reactions: ill_mannered

·
Registered
Joined
·
16 Posts
Discussion Starter · #5 ·
So it seems like you have a lot of problems to sort out first. Also I hope you are removing the boost/vacuum lines or pinching them before adjusting the FPR.
So, i forgot to bring this up as i just found this out yesterday when i was basically done taking out my throttle body, i noticed the expansion chamber or whatever the black box is thats at the firewall that connects to the plenum if the intake was not in. With that being said in theory, im assuming thats causing a vaccum leak which then wouldnt give my fpr enough pressure since it is also plummed into my plenum for vaccum. What do you think? I was going to test it out but like i said, i already basically had the throttle body out and was way too lazy to put it back in.

Loss of fuel pressure is likely due to something wrong in the fuel pump hanger. Could be that the wrong hose was used for the fuel return routing and it's not safe for submersion so it rotted from the outside in. Seen it happen several times before. It's very easy to remove the pump hanger to inspect it. I'd start there.
Ill check it but i got a line that was specifically meant to be submerged in fuel, but it dosnt hurt to check since my seats are already off. But read what i typed up top, do you think that could be the issue?
 

·
Registered
Joined
·
433 Posts
I would assume that's part of the problem, but even with a massive vacuum leak, you should still be able to raise fuel pressure by adjusting the regulator. Since you weren't, I assume the problem resides in the pump assembly.
 

·
Registered
Joined
·
16 Posts
Discussion Starter · #7 ·
I would assume that's part of the problem, but even with a massive vacuum leak, you should still be able to raise fuel pressure by adjusting the regulator. Since you weren't, I assume the problem resides in the pump assembly.
im just about to check it out rn, my tuner did say my pump was weak but i havnt heard a brand new walbro 255 failing that quickly though
 

·
Registered
Joined
·
433 Posts
im just about to check it out rn, my tuner did say my pump was weak but i havnt heard a brand new walbro 255 failing that quickly though
Lots of fake pumps out there now. I went with an aeromotive 340lph and it's quiet and sends plenty of fuel.
 

·
Registered
Joined
·
16 Posts
Discussion Starter · #9 ·
Lots of fake pumps out there now. I went with an aeromotive 340lph and it's quiet and sends plenty of fuel.
gotcha, ill keep that in mind! i was also looking at a walbro 525 pump but i heard id need a aftermarket hanger for that
 
1 - 11 of 11 Posts
Top