ls1charged

iTrader: (8)

So i got a 99 SS a little over a week ago, 75k miles, super clean! The car feels like its being held back.... hooked up HP Tuners and sure enough, it seems like its down roughly 40 hp!! We also noticed that after scanning each individual cylinder, we got multiple misfires in Cyl 1,2,6 and 7!! Since ive had the car i have done:
Tr6 plugs
Fuel Filter
Remove AIR and EGR
Seafoam
Lucas Fuel Treatment
Both upstream O2 sensors

Now everything has been detuned as far as AIR,EGR and rear O2's, but the car feels the same after all of the above! Also we threw it up on the lift and noticed that the previous owner put in a flowmaster muffler in place of stock and also removed only the drivers side CAT!!!?? After scanning we pulled #1 and #7 plugs, #1 looks fine however #7 looks lean, white as a ghost! Any input would be greatly appreciated! Thanks

ls1charged

iTrader: (8)

Any thoughts?

Raoul-Duke

iTrader: (6)

like a wet sponge?

ls1charged

iTrader: (8)

so after logging tonight we found out that the drivers side of the engine is running more lean then passenger side, also the O2 sensors dont seem to be switching as quickly as they should be, they are brand new! Do i have an electrical issue??

maf_diver

How quick are they switching? Post the logs and tune...

ddnspider

iTrader: (26)

Attached are the logs.
1) stock log with the pass cat and bad O2's.
2) new O2's and pass cat removed.
3) new O2's and pass cat removed with a different MAF.

The O2 voltages switch like crap and its not specific to one bank, although at WOT the driverside bank is marginally leaner than the passenger side, but that is going off the narrowband O2 voltage. Need to get a wideband on the car and see what it really looks like.

The tune is still basically stock. Only changes are to traction control, AIR/EGR removal, rear O2 codes turned off, skipshift, fans, etc.

Some other things on the list to check are voltage at the fuel pump, fuel pressure under WOT, check grounding, and AFR using a wideband.

maf_diver

The O2s look fine to me. Had to rescale the chart to see them (I don't use EFILive much though). They switch ok. Airflow numbers look ok, maybe a bit on the low side for sea level and 20 degC air temps, which could be dirty mafs or mechanical problems, or just strangled a bit by the exhaust. Try a compression test, but I'd guess it's ok.

It also looks a bit lean - check the fuel pressure. Hard to say without a wideband though.

Also look into a program called virtual dyno for testing power on the street. You need a flat road. Wouldn't trust those rwkw numbers EFILive is giving.

maf_diver

For comparison here's what I get with virtual dyno on the default dynojet "happy" setting. This is basically a stock LS1 with small shorty headers, high-flow cats, catback, tune.

ddnspider

iTrader: (26)

The car picks up random misfires and the O2s are way too jagged. I have noticed that stock fbody's do seem to have lousy looking O2s. For reference, this is what it SHOULD look like. Granted this car has long tubes, but you get the idea.

We are planning on getting a wideband on it as well as checking fuel pressure/pump voltage and see what happens. The fact that it still is seeing misfires proves somethings off.

ls1charged

iTrader: (8)

So today we checked voltage to the fuel pump, everything checks out! also swapped injectors from the cylinders that were misfiring to other cylinders hoping to follow a problem but some of the same cylinders still misfired as well as the cylinders that were not previously! Any thoughts?