Need help please problem with fuel...

[s13vette]

Ok so Let me start by sayin, I have read and googled everything about this but i have yet to find something that relates to my issue.

Now I have a STOCK 2000 LS1 A4 with ls6 manifold, truck coils, and ported throttle and tuned on HP Tuners on my 240sx. The issue im having and it started over night is this.

When i go WOT or just rev the motor passed 5000rpms it goes SUPER SUPER RICH from 11.5 to the 10.5 AFR. Now i dont hit a wall when this happends BUT it does break up all the way through the rest of the revs to 6500rpms.

What i have done so far. I have changed wires and plugs.
I have a log of the car on a WOT throttle i will post tomorrow.
I also opened the valve covers and the springs/retainers are not broken, and pushrods are good. But it does not feel like valve float but i could be wrong.

Car has no DTC's what so ever. But i have lost over 25 WHP when i put it on the dyno a week ago. Which is is really pissing me off.

If anyone can please shine a light or point me to an idea i can look into. Thanks I just want to take my car to the track and race the damn thing...


Here is a couple of logs as the name goes

[s13vette]

Update after i replaced the sensor i did a cylinder balance on the vehicle, and i also did a CASE relearn... I'am at a lost for words i have no idea what the issue is. I stepped on it after all of this today and the car runs random AFR's

Here is my tune sorry if u guys see anything wrong on the tune or log please LET ME ASAP... its driving me insane

I have ran the car with MAF disconnected and same problem occurs, changed the o2 on bank 1 and seem to be a bit better... i also have a stupid code p0719. If any of this is familiar or you have had the same or similar experience please share anything towards fixing this... I'am about to sell the car do to stress from buying a house and school and work and now this lol

[ingsteve]

WHy is your maf not linear near 8000Hz?
Did you tune the maf table?

[JamesLinder]

For certain your MAF and VE tables are incorrect with respect to values in the high RPM operating areas (too low now); looks like you reduced values in the areas of these tables to try and reduce your AFR however these changes are not the correct way to address the problem. I believe you either have faulty oxygen sensor(s), problems with wiring to the oxygen sensor(s), or even worse you may have a mechanical problem that is causing raw fuel to pass through one or more cylinders and cause rich readings on your wide band. Since you say you have checked and none of the valve springs have problems then you could possibly have a burnt or damaged exhaust valve that is not sealing when fuel is injected into one or more cylinders. Until you calm down, put the car aside and forget about it for awhile; believe me I know what it is like to become frustrated with trying to figure out a difficult problem like this. Less than one year ago I had an exhaust vavle break off its stem and go out the exhaust on my stroker only 10K miles after it was built. I have learned that having springs capable of withstanding the lift of your cam is absolutely essential or they will begin to allow the valves to float after a few thousand miles. I have had a lifter collapse when starting up a new build before getting the car on the street (thanks Comp Cams). If you were running nitrous and had your fuel too lean then you could well have damaged some exhaust valves very quickly and now they are not sealing. I hope this is not the case but it is probably time to run a static compression test on each cylinder before going any further.

[JamesLinder]

Just fyi, valve float typically is very repetative in that the cutting out occurs at about the same RPM time after time. In my case it occurred around 4000 RPM and sort of got better at 5000 RPM until several springs finally broke. Valve float can continue for quite a while before a spring finally breaks and then several usually let go within a short period of time. If you do not have dual springs and one breaks you of course will damage a piston and possibly the head when the valve hits the piston. With dual springs you will usually be okay. When valve float occurs neither the intake or exhaust valves are sealing well. A lot of times valve float will cause the engine to vibrate or shudder and it can feel like the torque converter is messed up but this is of course not the problem. Good luck.

[JamesLinder]

Until you get your motor figured out, I would disable the nitrous system, set the timing back to stock, and change PE vs RPM to about 1.16. This should get you an AFR of about 12.7 if there are no mechanical problems. I would only reactivate nitrous and of course reduce timing back to 24 in high RPM area of the timing table and richen up the PE ratio after I had the car completely straightened out.

[s13vette]

thanks alot for the help man. Well you are sayin the MAS is off and i must say i have had an idea that the MAS is bad.

Here is the deal. The car has been running Great for the last 1 1/2 year. This thing happend after the car was down for a about 3 weeks while i was rebuilding my transmission. When i got the car running again Is when i noticed the issue of running rich PEG rich and heavy miss at 5000rpms...

After looking close at the log i have above i noticed the Bank1 o2 sensor was done for. I replaced the Bank1 O2 sensor on friday and today i gassed it. It did not break up like it did before but still air and fuel went down to 12.3ish...

I was told to look at the COT tables... but i have no idea about HPtuners just learning.. and my tuner is no longer living in miami so there is no way for him to help out.