DarrellGS4

I'm now having this same issue. 3 weeks ago installed a new fuel filter and fuel pump (walbro). Car was running great. Then all of a sudden, it would barely start...trouble accelerating and loud popping / backfire sounds when I step on the gas.

So went autozone, codes indicated O2 sensors...had a shop change all 4, install ppe headers and new mounts. Problem still there.

Any thoughts?

F4A22

iTrader: (14)

Throttle body or ecu.common problems with these cars.i have an ecu text me 863-537-0196

burny

Accelerator pedal position sensor, throttle control motor or throttle position sensor. Read in the performance section under limp mode. There is a PDF file that tells you the operating specs for these 3 sensors and you can use your multimeter to test each one. Before I did any of that, I would replace that cracked resonator box you mentioned. There is a link in the performance section on this too.

burny

read post #419 first in link below and if that doesn't fix problem, start checking throttle body sensors.


https://www.clublexus.com/forums/per...mp-mode-5.html

MasterKwan

I'd argue you screwed up the fuel pump install since all of this started with the new fuel pump. You need to get someone who knows what they're doing to actually trouble-shoot this problem. First thing I'd check is fuel pressure. It's likely you simply wasted your money on those 02 sensors.

DarrellGS4

Thanks MasterKwan...but I had a shop put the fuel pump in. Sorry, my reference to installed was meant to be it was installed. It was my first thought too...but the symtoms do not see like weak fuel pressure. I'll be sure to have that double checked at the fuel line.

I'm leaning real hard on APP or TPS.

Here is a video of the issue...no codes at first, but when I pressed the pedal I could not go past ~5-10% without an issue. Lucky me I have a SAFC installed and the throttle gauge on it seems to work as I can see it reading the pedal position as I step on the pedal.

mIS

Any update on original poster? Problem resolution?

MasterKwan

The throttlebody has 2 TPS's. One for your pedal and one for the the amount the ECU opens the throttle. You can test the TPS with a volt meter.

What's happening in your video is that the ECU isn't commanding the throttle body to open. Normally you step on the pedal, the accelerator position sensor tells the ECU "I've stepped on the gas" then the ECU commands the throttle control motor to open the throttle. It measures how much it opens the throttle with the actual throttle position sensor, mounted on the other end of the throttle body. This is the way the IS300 works too. Once you step on the gas beyond 50% or so, there's a mechanical failsafe that presses the throttle open. It's probably enough to limp a car home.

I'd check both sensors with a volt meter before I spent any more money.

shakky

what was the fix for your gs300, mine is literally having the same problem

JaySco

I applaud you doing research to find threads, but you are asking questions to people that haven’t been on here for years, 10 years in this case.
Just. Relate a new thread and detail what the issue is.

shakky

okay i tried that but i guess now i know more info now, no one really replies though