My car is idling lean, the wideband is all over the place, sometimes as lean as 17.0 and off the wideband. The car seems to drive fine but it is going way lean at WOT at high rpm. The wideband looks fine under WOT until about 5k rpm then it quickly ramps up past 15.0 and I let out as quickly as possible for obvious reasons. The only code the pcm has thrown has been po121 and po122. Both are TPS codes, I put a new TPS in the car and it still has the same issues. Is there anywhere else I should be looking? Another sensor on the same circuit as the TPS maybe? The car ran perfect before this, it has been tuned for a couple months now and I drive it basically everyday. Thanks in advance for the input.

BTW this is a pullout from a 2001 SS camaro.

 

I would check the fuel pressure since it's lean all over the place. This is also assuming that the tune is good since we have no idea what it looks like. Also sounds like you have a wiring issue to sort out on your TPS circuit. If you need help on how to properly diagnose that, let me know.

 

How do I diagnose the issue with the TPS? My bet is that it is a wiring issue, I have to deal with wiring issues before on this car. I did check the gray wire for 5volts and it was good. And my signal works because the nitrous controller is confirming WOT, and the ground worked fine.

Also, I have checked the fuel pressure at idle and it is at 59psi, where it should be.

 

Have you messed with the set screw on the throttle body? What are your tps volts at closed throttle. Has it always ran lean or is this a new thing?

 

This is a new issue, the car has been fine for a couple months as it got a cam, full exhaust, and bottle over the winter. Are you refering to the signal voltage? If so it is .83 at closed throttle, and the gray wire is at 5volts all the time.

 

To the top

 

if you're only going lean at high flow situations, i'd bet it's the fuel system not catching up. whether it's the pump itself, or the voltage going to the pump, something's not up to the task

 

Just did a new pump, new filter/regulator, checked the voltage at the pump, everything was in check. Threw a bunch of fuel at it up top using hptuners, same issue. Leans out off the wideband.

 

Sounds like you need a new O2 sensor.

 

O2 sensor on teh wideband or regular narrowband? regular narrobands are ignored under WOT. and a wideband sensor wouldnt stop working correctly only under heavy load, while working fine under other conditions.

 

What is your commanded AF ratio in your Idle and WOT portion of the table set to?

 

WBO2 of course.
After adding fuel and still showing lean, this is were I would look first.

 

I replaced the WB sensor today, still reads the same. I shouldnt be seeing over 13.2 at WOT. Im not sure what the commanded AFR is at wot, but it shouldnt go over 13.2, thats for sure. Its a pretty safe tune, cus its a nitrous tune.

 

Is your TPS 100% WOT?
What is your PE vs. TPS set at?
Try resting your TPS.
- Turn car off
- Remove TPS Sensor wire harness
- Turn car to ign position (DO NOT START)
- Wait 30 seconds
- Turn ign off
- Plug in TPS Sensor wire harness

 

TPS is fine, it resets to 0 percent or however it is measured. We were messing with the idle yesterday, drilling the throttle body blade to bring the IAC values down, the tps reset just fine everytime. The tps signal is fine, it is getting 5volts, and the ground works.

I got different injectors, I might try that.

 

sorry to bring up a dead thread but this is the EXACT problem im having with my ls1 240sx and i cant figure out what is is. im going to replace the 02 sensors and tps but im wondering what ended up being the problem? it would save me alot of time and headaches. thank you

 

Sounds like a great idea. Throw parts at it without doing any real diagnosing.


You can not diagnose modern EFI systems without the proper equipment. If you don't have the means or tools to do real diagnosing, then take it to someone that does and has the knowledge to analyze the data.

 

^ 100%. A scan tool or HPTuners/EFILive. Being able to log everything that goes on makes tracking down issues SO much easier. I had the Denso Supra pump for a long time. It finally decided to die. Not the bullet through the brain die but rather the slow old man I'm going to take 4 weeks to die die. I progressively lost fuel pressure until I was finally down to 10psi and the car couldn't idle anymore. The first thing to go was WOT fueling. Thought it was a clogged filter at first. Didn't help.

 

my tuner is the one who recommended these parts because he couldnt figure out the problem. i didnt tell the entire story because its long, so before you are condescending make sure you know the whole story or ask for me to specify.
i have a scan tool and am installing a wideband soon but i wanted to get a quick response on the actual fix before i try and diagnose.

 

the story i was avoiding telling is that my tuner said my car is stuck in closed loop and wont go into open loop at WOT and when it hits 4500 rpm the afr spikes (exactly like the original post's problem). he smoke tested the intake manifold and found no leaks. i have pending low and high voltage codes for my tps and my friend had a similar problem and it was his o2 sensors. i did get the proper diagnosis and do have the proper tools to find the problem, im just trying to see what his fix was so it saves me time. thank you for your awesome tone though it really helps.