germ79

Ok, trying to get to the bottom of this high LTFT on Bank 2 only at idle. If I'm idling, the LTFT for Bank 2 skyrockets. This also happens if I'm driving and put the clutch in and coast, letting the rpms go down to idle speeds. I've been looking for vacuum leaks, but haven't found any. Only thing I did find was that the crank case breather tube (from throttle body to crank case) is cracked. My understanding is that this is not a vacuum line, so this shouldn't be the cause.

Here is an excel file with the LTFT figures and a chart. The green line is the RPM's, the blue is Bank 1 and the red is Bank 2. If anyone has a thought of what I should be looking for, please let me know!

I've also attached the csv file with ALL the info and a jpeg of the chart...although you'll have to zoom in because it is really long!

ANY help will be so very appreciated!

Injuneer

The LTFT's are developed for each of the 18 cells in the system. Idle is Cell #16. That is only used when both the MPH and the TP% = 0. Decel, throttle closed but vehicle still moving it not using the idle cell... typically you will get Cell #17. So you won't see the same LTFT while coasting with the throttle closed as you will with the car at rest and the throttle closed. Cells #0 - 15 are used based on engine RPM and engine load (MAP).

The log has a lot of problems that prevent much in the way of analysis. The logging interval is about 1 frame per second. The PCM is updating at about 9 frames per second. The log does not show what cell the engine fuel control system is operating in. And other things that may be important are not shown - MAP, MAF g/sec, etc.

You have a very large cam (although "24x" doesn't really tell us much about it). Are both intake and exhaust durations the same? What is the lobe separation angle? This affects overlap, and overlap it idle can dump air into the exhaust, causing the PCM to add fuel the engine really doesn't need. Who tuned it for the cam? Left and right bank LTFT's may not be the same at idle with a big cam, due to reversion.

Are you possibly running open headers, allowing the backwash of air at idle to contact the O2 sensors?

One minor question.... have you checked the fuel pressure at idle? The Aeromotive AFPR's are not particularly reliable.

The PCV air supply line from the throttle body to the valve cover is intended to flow air that has been measured by the MAF sensor, since that air ends up in the combustion chambers. The air is pulled through the line by crankcase vacuum, developed from the vacuum source for the PCV valve. So a leak in the air supply line means the engine is using vacuum to pull in air that has not been measured by the MAF sensor, which forces the PCM to add fuel in response to the resulting lean condition. That would not account for the 25% extra fuel being added by the LTFT.

germ79

Thanks so much for the reply. Here's some info:

1. The car was tuned by Solomon. I reached out to him today to see if the original owner had given him the cam specs (he didn't give them to me). He had the specs as 48-254/111 w/ .552/.571 lift.

2. Hmm..I'm new to data logging and am not sure my setup can give me all that info, but I'll check and see what I can do.

3. I haven't checked fuel pressure because I thought if it were a fuel pump or fuel pressure issue it would affect both banks, not just bank 2. I have a fuel pressure gauge I can test it with. The car no longer has the schrader valve...so would I check the pressure at the fuel filter or attach it near the FPR?

4. No open headers - full exhaust with headers, y-pipe, over the axle into a magna flow muffler and dual tips out the back.

If I can, what measurements do I want to get for a log to be helpful for diagnosis?

Thank you for the time!