ssduane

iTrader: (3)

For a while my ST and LT fuel trims have been going high (+25) while my O2 sensors are reading lean 50-100 mV's. Most people said exhaust leaks which seemed understandable considering I made headers for the car. Pulled them off and had some leaks at the collector to head pipes, not big but leaks. Tried rewelding but couldn't get them to seal up and said screw it and bought some TCI LS1 headers which I assume shouldn't leak. But I'm gettting the same thing, almost, takes a bit longer for the ST/LT fuel trims to go max but they still do.

O2 Sensors get good voltage and ground (fixed a ground on B1) and no codes.

Could it be soemthing on the intake side? Vacuum leak? I can't see anything or hear any, all ports not used are covered. New MAP sensor seal installed, intake cgaskets and throttle body gaskets look good. Maybe the port where the MAP sensor goes? O-ring in there? It spins but can't seem to get it to come off (LS6 intake).

MontecarloDrag

iTrader: (3)

Some headers trick the sensors and make them read a false lean.
Sometimes the sensors are too cold to operate properly and they dump fuel until the trims are maxed (while still reading lean)
You may need tuning to solve the issue, unless you want to wrap the headers to make the O2 work hotter

edcmat-l1

iTrader: (10)

Low fuel pressure.

ssduane

iTrader: (3)

Will put on fuel pressure gage and check tomorrow.

ssduane

iTrader: (3)

fuel pressure runs 58 psi idling, drops to 56 when hitting throttle and quicklly comes back up, so fuel pressure is not an issue?

Any other idea's? COuld my tune be that far off to affect this?

edcmat-l1

iTrader: (10)

It's possible the tune is off bad enough to cause that. If the injector flow rate was way off it could do that.

ssduane

iTrader: (3)

Doing somemore research and reading and saw that O2 sensors do not operate properly till 360 degrees C, 680 degrees F. Which is mentioned above about could headers. Could this also be a problem as I am not driving the car (still in mock up/getting everything functional before I tear down for paint) and only idling it in the driveway. Basically I'm just trying to get good idle throttle response and off idle response in gear and not have it fall on its face.

Been comparing my tables to other tunes and stock MAPs, good thing is all this reading is making me somewhat more aware of what the hell does what.

lt1pwr1

iTrader: (1)

Check for vacuum leaks like around the intake. Unless I am understanding incorrectly, the computer is dumping fuel to compensate for the lean condition which is being read by the o2 sensors?

In that case, I don't see conflicting data really. You are running lean and need to figure out why.

Also, definitely check/clean your MAF. I've seen those give a false read to the o2 sensors. If you can, swap with someone and see if the problem goes away.

jimmyblue

iTrader: (11)

Headers cool the sensors and the gas that feeds
them, they go sleepy and start lying to the PCM.
The older they are, the worse they like the cold,
and the longer they lie about mixture, the more
they soot up and get worse.

You can see if this is it, by watching the O2 signal.
If you have good dense switching when you first
drop to idle, and it slowly gets lower in switching
frequency and less tight / symmetric, blame it on
the heat situation.

Which there seems to be few good fixes for, other
than running open loop, if you want to keep long
tube (high surface area) headers.

ddnspider

iTrader: (26)

I recently asked about O2 switchpoints over on the EFI Live forums. I got some great responses and info. For starters, change you switchpoints to 450mV for all closed loop modes.

Another big one was updating B4113 STFT base delay. When you move the O2 location further away from stock, then you need to increase the time before the O2 mV is read by the PCM.

You probably have more than just these things going on, but it would be a good idea to change them anyways.

ssduane

iTrader: (3)

Got home today and put the *** end on jack stands and ran and scanned it in gear to get some heat to the headers/02 sensors and they started tracking, sweeping back and forth and LT and ST trims started getting lower. Not where I want them but I think I am satisfied that everything works properly and I just need to dyno tune it, or get the PCM to someone that knows what theya re doing to mail tune it for me.

Thanks for all the information!