DRIVEFASTKEEPLEFT

I've been dealing with a rich condition for awile now. Can someone look at my readings and tell me what you think? Everything look okay? The car is 95 355 GM 847, ported heads-52mm tb,headers, x pipe duals. It is a mail order tune.

Cold start-Open loop-------Warm Closed loop--Warm Closed loop idle

RPM-1051-----------------6657----------------877
TPS Voltage-.47v----------4.73v---------------.43
Spark Advance-30 deg-----38-------------------29
IAC-100--------------------104-----------------60
BLM Cell-16-----------------15------------------16
LM Enable-NO---------------no-----------------Yes
Injec Bank 1-5.6 msec------15.1-----------------3.0
Injec Bank 2-4.5msec-------15.4-----------------2.0
LTFT Bank 2-128-----------128------------------109
Learned IAC-50-------------50-------------------50
Left H02s Bank 1-.59mv-----.93mv---------------.02mv
LT Fuel trim Bank 1-160-----128------------------160
MAP volts=2.31--------------4.49-----------------2.67
Manifold Ab Pres- 16 inHG---28--------------------18
Mass air flow-11.9 grs--------99.9-----------------7.5
Right H02s Bank 2-.71v------.87-------------------.35v
ST FT Bank 2-128-----------128-------------------130
ST Fuel trim Bank 1-128-----128-------------------130

Injuneer

Not a lot to be learned from a single frame for each operating condition. But a few things show up:

1 - You have a major case of "split BLM's".... 160 on the driver's side, 109 on the passenger side at warm idle. Cam can cause that, or an aftermarket throttle body.

2 - At WOT, recognizing the limits of the stock narrow-band O2 sensors, you appear to have a rich condition on the left side (0.93V) and a not so rich condition on the right side (0.87V). A difference of 0.60V from side-to-side is excessive. Its odd that it came out that way, when the PCM has defaulted to 0% correction at WOT in Cell 15 (128 BLM's), and the injector pulse widths are slightly longer on the right, but its running leaner on the right.

3 - Definitely something wrong with the MAF sensor. The mass air flow at cold (11.9 g/s) idle and warm (7.5 g/s) idle looks OK.... but if the engine was actually at 6,657 RPM at WOT, there is no way you would see 99.9 g/s. It would probably be well over 300 g/s.

DRIVEFASTKEEPLEFT

injuneer. Thanks for the reply. I'm suppose to get the car dyno tuned next week and I wanted to make sure that all sensors are okay. I just put a new Summit 52mm TB and the car has a gm847 cam. Would the car be running richer since the MAF isn't reading right at WOT? It's ported and de-screened.I guess I'll have to track down another MAF to see if this is this one is bad. Should I do the drill mod? Let me know what you think.

Injuneer

Are you sure it isn't just a typo or a bad reading on the MAF at WOT? If it actually read 99.9 g/s, the PCM would only be putting in about 1/3 of the required fuel and it would die because it was so lean.

Split BLM's only affect the fueling at low rpm, part load. To tell how bad the problem is, and what it is affecting, you have to do a data log that shows as many of the long term fuel correction cells as possible. Hopefully, not right after the PCM has been reset, and the long terms haven't had a chance to fully develop.

My observations are based on a VERY limited amount of data. As I said, you can't learn a lot from a single frame of data.

DRIVEFASTKEEPLEFT

It's a friends scanner and I'll look at the MAF closer. I guess I'll take it to the shop and see what my tuner can do with the car. Again, thanks for the input.