Hey guy can I get you input on the following issue:

Today I go to start my Trans am that has been sitting in the garage for a full day without driving and it has problems starting. When it finally starts and I try to get the car to move in reverse the RPM's drop to 500 and the car dies on my on two different occassions even when I give it gas. The car is stock except for a Diablosport Performance tune and a Magnaflow Cat-back Exhuast. This has never happened before and when I connected the Diablosport to the car to monitor the LTFT it was over 15% on both side with the car on idle I don't remember the LTFT's being that high before!

Any input would be greatly appreciated.

 

Your front O2's might be on the way out. Try reseting the PCM and see if that helps (pull PCM/BAT fuse under hood for 10~15 minutes and replace).

 

I have reset the PCM back to the factory tune and still see the same issue? Do you still think that I should reset the PCM SSpdDmon? If you I will try and will post my results.

 

If you reflashed the tune, it should have zero'd out the trims. I wonder if you could move the O2's around and see a difference (i.e. move the fronts to the back and the backs to the front)? Such a stock car on a stock or Diablo tune wouldn't have tuning problems. They'd be more related to mechanical/electrical problems.

 

I just took it for a test drive and noticed that one of the O2 sensors in bank 1 had erratic readings at idle and while cruising. It went from being at 700 to 500 to 95 to 650 to 300 and so on, while the other sensor was steady between 650 to 740 with little change what so ever at idle or a steady cruise.

I do recall the SES light came on and a code for the O2 was retrieved about 3 months ago. I deleted the code and the car seemed to work fine without any problems and the LTFT were not as high.

Should I interchange the o2 sensor in bank2 with the o2 sensor in bank1 that is reading erratically? Would that help? I did noticed that the sensor in bank2 had some of the same readings as did the sensor in bank1 with the erratic readings. Would that be a problem? or is it expected due to the reading from the sensor in bank1.

Hey, thanks for your help, SSpdDmon!

 

That sounds like your problem right there. They're supposed to fluctuate above 600mV and below 400mV. That sensor sounds like it's about dead. Ideally, when you replace a bank 1 O2 sensor with a new one, you really should replace both sides. So, start saving...

 

I inspected the o2's and they seem to be working fine, so i started to look for leaks but I did't find anything initially. I took the car for a drive and noticed that my LTFT seem to have improved (from 15% to 9.38%)for no apperant reason in both banks at idle. I was getting low on gas so I decided to fill the gas tank and continue monitoring the fuel trims. I notice that at a cruise the LTFT stayed around -2.43% and 3.14% in both banks, could my gas have something to do with the LTFT????

It's really humid here today and as I was driving I notice that my windshield was fogging up from the outside. When I got home, I inspected for leaks and the AIR hose had a big tear and was leaking air. I will be replacing this hose and monitor my LTFT. I still don't understand how it could be affecting my LTFT's though?? Can anyone shine any light into this???

 

1) After you fill up, there is an increase in vapors/pressure in the gas tank. The EVAP system activates during closed loop to pull some of those environmentally unfriendly gasses from the tank up to the intake so they go through the combustion process. This is normal and will cause the trims to drop ~10%.

2) If you have a tear in the AIR hose, it could be letting fresh air into the exhaust. The O2's would then see the fresh, unburnt oxygen and tell the PCM to add fuel. That may be the source of your problem.