Stockish 99 SS M6 log- Something feels off

[ddnspider]

Attached is a log of a stockish 99 SS 6 speed car. The car has a flowmaster, no EGR/AIR/throttlebody bypass, no rear O2's/ TR6's/ K and N air filter. The previous owner removed the driver side CAT. I removed torque reduction, traction control, lowered fan temps, removed skip-shift, basic stufff. By the looks of the logs and the way the car feels, it just feels like its being restricted or held back. The MAF lb/min also seems low for the car. Once he gets headers and replaces the flowmaster I will do a MAF tune on it, but just looking for ideas on other stuff to check. I almost don't trust the front O2's when he went WOT since it looks like it goes lean, but shows no knock and hes running 26 degrees of timing. Ideas of things to check are welcome.


16220

[ddnspider]

bump....had the passenger side cat removed and the car seems to have picked up but it still feels a bit down on power. I had him disconnect the MAF and it definitely felt faster and the O2's actually started to switch like a "U" instead of the jagged look in the log above. Still looking for ideas, maybe a clogged fuel rail/injectors?

[joecar]

Any powertrain DTC's...?

[joecar]

From log I see MAF is under-reporting.

[joecar]

I suspect the K&N filter has shed some oil onto the MAF.

[ddnspider]

16230
16231
The car had a code for a cat, which was prior to me turning off the rear O2's and us removing the pass side cat. Otherwise the only code that came up when I scanned it was a data link code, but I assume that was related to me having EFI Live plugged in. Something else interesting, I thought the MAF frequency was low, so I unplugged the MAF and the car seemed to pick up, but I didn't have a way to correlate power/airflow and forgot to log dyncylair.

It feels like there are multiple issues going on. Removing the pass cat was the first variable to get rid of so the banks were balanced. And the car went from ~28lb/min to 30-31. But that still seems low to me. I have a spare MAF, albeit descreened. We may try throwing that on the car and see what it does. I also think there is a fuel issue. Either the voltage is dropping or the pump may be flaking out at WOT or something is clogged. The first log is with the cat removed and the 2nd log is no maf. Look at the O2's switching difference, especially with the MAF off.

[joecar]

Measure rail pressure and fuel pump voltage as engine load changes.

Change fuel filter.

I'll be looking thru your logs shortly...

[ddnspider]

Measure rail pressure and fuel pump voltage as engine load changes.

Change fuel filter.

I'll be looking thru your logs shortly...

Measuring fuel pump voltage is on the agenda for tomorrow. Fuel filter was changed a few days ago to rule it out. Also going to work on a way to measure rail pressure.