Look at what DataMaster does with the logged data.... frame by frame review, and a graphic representation, selectible binary flags, etc. Not that you can use it, but it does show what is available.

Personally, I also like to download the data log to Excel, and manipulate it, put the columns of data in the order I prefer, work with column averages, highs, lows, color code trouble areas to look for relationships. For OBD-I LT1's, both DataMaster and FreeScan can provide a usable data file.

 

Swapped the 02 out with one of the rear o2s and it changed nothing. Bank 2 is still running the same fuel correction %'s. I looked for exhaust leaks again and found none. Even laying under the car while running. I also removed the Passenger side injector clips one at a time while running to see if one injector was dead. All were functioning. I also checked the one way valve to the Passenger side AIR injection and it was working, however, the pipe for the pass. side has an inlet to the back of the intake that would not be closed off by the pass side valve. I know this is factory, but how does the pipe to the back of the intake get shut off from the pass. side manifold?

 

How did you swap front and rear sensors - they have different connectors?

Do you mean the corrugated tube that connects the back of the intake to the #8 runner on the exhaust manifold?

http://shbox.com/1/egr1.jpg

That tube has nothing to do with the AIR system, and does not connect directly to the inlet air plenum of the intake manifold. It connects to an internal passage in the manifold that leads to the EGR valve. The EGR valve controls exhaust gas flow from the exhaust manifold to the intake manifold air plenum.

BUT.... if the corrugated tube has a crack in it, or the gasket at the intake manifold is leaking, or the connection (no gasket) to the exhaust manifold is leaking, it will allow air to be sucked into the pipe by the exhaust gas flowing past it in the exhaust manifold, and that will cause the O2 sensor to read lean, and the long term corrections to elevate.

 

O2's are the same on vettes, part #'s are identical. The AIR is also plumbed differently than f-body, I'll try to post a link to a pic. It sure looks like the pipe goes directly from the intake to the exhaust with no valve. Also, no EGR on LT4's. Something about the cam phasing allowed them to delete it.

http://s88.photobucket.com/albums/k171/budnik0577/AIR/

 

My apologies.... I forgot that wayyyyyyyy back in the first post you mentioned it was a Corvette. You really need to add a signature so people know what you are asking about, and don't waste their time trying to help with a car they are not familiar with.

 

I appreciate your help, your Ltx knowledge is part of why I asked on this forum, but I'm just trying to diagnose something that is difficult and providing as much info as I can remember. I intended no sarcasm in my response. (not sure why I deserved any in yours)

My Pass. side cylinder bank is running lean and I can't find the cause. I've ran through the FSM to no avail. The AIR system runs a pipe directly from the back of my intake to the pass side AIR pipe that is then plumbed into my manifold. I don't see how this can be, unless there is a one way valve in the back of the intake that blocks off the exhaust gas? The FSM doesn't show anything. How can the AIR pump directly into the intake? It pulls the air it injects from the plastic plumbing before the MAF. I must be missing something. I think I'll take it apart to check it out. This is driving me nutz. I have no AIR codes, and if it is malfunctioning, it is supposed to set them. Maybe I should just delete the AIR and program it out.

 

You didn't. That was a typical response to being wrong. It's always someone else's fault. After reading the response, not the sharpest knife in the drawer either.

I'm curious why you didn't swap the O2s side to side? If the front O2 was bad, chances are good the second one on that side is bad also.

I don't see how the fuel trims could be off if the O2s are swinging like they should be. Therefore, I would also suggest you test the wiring for shorts or opens. Easy to do with a scanner and a paper clip. No need to ohm wires.

 

I found a diagram of the Corvette LT1/LT4 AIR system in the Probst Corvette Fuel Injection book. It shows a split in the passenger side AIR pipe, with one branch to the exhaust manifold, and the other to what appears to be the back of the intake manifold. But the diagram doesn't show exactly where it connects. Since my LT4 intake has all the same bosses and holes as my LT1 intake, it would appear that the connection of the AIR system to the intake manifold goes to one of the ports used for EGR on the LT1. Looking at Shoebox's photo that I linked, which port does the "extra" air connection bolt to - I suspect its the one with the corrugated riser tube (that would be a flow pattern similar to the 93 F-Body LT1)? On the LT4 manifold, is there a blocking plate over the EGR valve port?

It seems that the same pipe was used on the LT1 and LT4 engines, but the flow into the intake manifold is blocked by a plate over the EGR valve port.

 

Speedy, I should have been more clear, but I did swap the rear o2 from the oppisite side to the front 02 on the pass side. It made no difference, at idle, the pass. side runs like a 15-20% short term fuel correction. This is right on the edge of setting a code. When I delete the code it will take a few trips to come back, and I have even seen the light go out occasionally. I just cannot find the cause.

Here is a look at the back of my intake. The port on the pass. side connects to the AIR tubing. The port on the driver side is blocked off, and I believe this is the EGR port on LT1 corvettes.

http://s88.photobucket.com/albums/k171/budnik0577/AIR/

 

That connection is for the EGR riser tube, and it would function that way, if your LT4 had an EGR valve. But because is doesn't require the EGR system, they put the blocking plate on the EGR port. A leak anywhere in that pipe, AFTER the check valve, will admit air to the exhaust.

 

So, the riser tube is connected directly into the AIR. Is the riser tube port also blocked in some way, or does it actually allow air/vacuum directly into the AIR tube?

 

The riser tube port does not connect to the intake manifold air plenum. There is an internal passage that connects it to the EGR port. The EGR valve has to open to allow the exhaust from the riser tube to flow into the intake manifold air plenum. As long as there is a well-sealed blockoff plate over the EGR valve port, no exhaust or air can flow into the intake manifold.

Apparently the Corvette system mimicks the 93 F-Body system. The connection to the #8 exhaust runner serves two purposes. When the AIR system is operating, air from the AIR pump flows into the #8 exhaust runner. It can't flow into the intake manifold, because the EGR valve stays closed when the AIR pump is running. After the AIR pump shuts off, the exhaust can flow up the tube from the #8 runner to the back of the intake manifold, where the EGR valve is pulsed open to allow the exhaust into the intake manifold air plenum. On the 93 F-Body LT1, they only had one AIR connection on the passenger side manifold, and that was the #8 runner. Apparently the Corvette uses two ports on the passenger side manifold. But the function is the same.

On the LT4, they could have simplified the system by deleting the connection to the back of the intake manifold, but they cut a lot of corners on the LT4, apparently because they ran out of development money. That was the story I heard from someone who was involved in the development of the heads and intake manifold. They finished the heads, but they never finished the intake manifold. Put more metal at the top of the manifold runners to allow the taller ports to be used, but never enlarged the ports in the LT4 intake manifold, leaving a major mismatch on the manifold port and the head port.

 

Thanks Injuneer, that clears up the port issue. I did know about the intake port mismatch, as alot of guys take the intake off to grind and match the ports. I wonder if there would be a way, perhaps with some sort of soapy water, to check for leaks on these rear intake ports. I could maybe throttle up the engine to see if any exhaust gas is getting through.

 

The problem with leaks in the exhaust system is that the exhaust gas moving at high speeds past the leak create a vacuum that sucks ("educts") air into the leak, diluting the exhaust.

 

This would explain my lean condition, if I had an exhaust leak. Would this show up at idle with low exhaust pressure? I've had exhaust leaks in the past, (on different vehicles) and they were readily identifiable due to the noise they made. No such luck this time.