LTFT at 128-130... until the EGR Opens
 

I understand that the EGR is introducing exhaust back into the intake to help cool combustion. It is a moderate cam with 230/236 @ .050" duration.

Everything is fine until the EGR Opens. When it does, my Left Bank goes straight to 143 and stays there. The right bank is still 128-130. Is the EGR dumping into one of the banks only? Is the overlap affecting EGR distribution?

I'm tempted to turn the EGR off and see what it does, but I can't get to the car until the weekend.

1995 Z28 M6.

actually the egr system is an emissions only thing, it recurculates exhaust back in the motor to reburn it, and help burn up the hydrocarbons (unburned fuel) to reduce emissions. i would also turn it off and only turn it back on for emissions testing, unless the cops have moble sniffers.

After more research, the LT4 had block off plates for the EGR. I suppose that was due to the cam and the amount of overlap creating a natural EGR.

Since the cam I'm using is a CompCam 467 with 230/236 duration, there is plenty of overlap and perhaps the EGR is adding too much... it isn't distributing evenly and it seems to be dumping into the driver's left bank when it opens.

This causes the left LTFT to go to 142 when it is open and the right side stays normal.

I'm considering turning it off over the weekend when I get back to the car to see if the EGR has an effect when it is off.

I'm all for the benefits of the EGR and believe it is helpful, but there may be enough overlap already with the cam.

Minor technical point, but the original poster is correct. EGR recirculates exhaust gas to reduce combustion temperatures, when the engine is operating under conditions that promote the formation of NOx. It is not used to control unburned hydrocarbons. Controls emissions, but not hydrocarbons.

Is it possible you have a leak in the EGR riser tube or from one of the gaskets on the manifold? When the EGR opens under command of the PCM, the PCM has to reduce fuel flow for the fact that air is being displaced. If its pulling air in through a leak, and not exhaust gas, there isn't going to be enough fuel, and the O2 sensors will pick up the extra air flow, and the PCM will raise the short term fuel corrections, and then the long tern corrections to supply the extra fuel.

Great idea. The upstream pipe is wrapped in header wrap. I suppose the best method to test is to remove the pipe off the header and insert a blocker plate.

Any other ways to check the upstream pipe? It is a pain to get to on the headers.

Why not just delete the whole EGR sysytem?

He lives in the People's Republic of California.....they have to have all the emissions stuff present...