afasttransam

iTrader: (1)

I went to the dyno the other day to get my car tuned. I bought brand new ngk o2 sensors. We put then in at the dyno. On a cold start we where getting different pulses from both sensors. After we ran the car kinda hard for a few min we started getting the reading from both sensors. After the car set for a little bit we go diff reading from the sensors agian. It was nevertheless same though. The readng would always flip flop sides. Same thing after we ran it hard we go the same readings. Anyone else heard of this?? Should I get factory gm or Bosch sensors. Any help would be great. We all kinda stumped on this.

Intimidator02SS

I was under the impression that gm used the ngk sensors originally.
What was wrong with your old sensors?
Are you trying to tune it on the dyno with your narrowband sensors?

afasttransam

iTrader: (1)

I have a wideband in the car. The tuner was just trying to get reading so he can finish my cold start tune. I am not sure what they use factory for sensors All my problems are when the car is cold. Tuner thought it was bad heaters in the o2 sensors

BLK02WS6

iTrader: (2)

When the car is cold, it is in open loop and the O2 sensors don't effect the tune... when it warms up, it goes into closed loop and then the O2 sensors come into play. A good tuner should know that...

afasttransam

iTrader: (1)

my problem is when the car is cold it idles ruff and keeps throwing o2 sensor codes. the tuner says the left bank is running real rich and the right bank is lean. he says the o2 sensor reading in the pcm is getting diff pulse rates from the sensors.

blk99sleekbeak

iTrader: (2)

my car does this too. It throws the fuel trims off at idle too. Havent checked it at WOT yet though. The drivers bank o2 sensor shows hardly any voltage at idle. and is slow to come up when you give it gas. It has a strong smell of unburnt fuel at idle and a slight studder down low when cruising but clears out after about a second. I replace the sensor a couple of weeks ago and it helped with the smell and studder but it came back this past weekend.

BLK02WS6

iTrader: (2)

My point is that when the engine is cold, the O2 sensors do not feedback to the PCM and change the fueling at all - when it is cold, it is running strictly off of the tune your tuner has put together.

If it is running rough and when it is warmed up, and the O2 sensors are showing split readings (better judged by the LTFTs than sensor readings), then that indicates that you have exaust leaks that are basically fooling the O2 sensors into thinking it is lean, and therefore adding fuel that isn't needed and making it rich...

BLK02WS6

iTrader: (2)

Sounds like you have exhaust leaks too... check the drivers side - its showing lean at idle (that's when exhaust leaks show up the worst on the O2s). That's likely a false lean signal that is causing the drivers side LTFTs to go up (adding un-needed fuel)...

blk99sleekbeak

iTrader: (2)

I do have an exhaust leak were the collector meets the y pipe. Didnt realize that a small leak would cause something like that. I will be pulling the y pipe off in a couple of weeks to do a transmission swap anyway. Ill make sure i get it all sealed up nice