LT1 with 24X tuning problems

[nskaats]

I need help trouble shooting my 1994 LT1 with EFI connections 24x ignition system. For anyone not familiar, the 24x system converts the LT1 over to the LS1 PCM and ignition system.

Engine details:
355 CID LT1
Compression is 11.3:1
Comp Cams XFI grind 242/248 @ 0.050" lift, 0.584/0.574 lift, 113 LSA, installed at 111 ICL
Stock heads, 3 angle valve job, valve bowls blended and port matched
Ported intake manifold, 58mm throttle body, hooker longtubes, custom y-pipe, and borla cat-back.
This engine has about 2,500 miles on it and ran great before the 24x conversion.

We had this car running great before I installed the 24x system. I installed the 24x components, modified the factory harness for the new components and re-pinned it for the LS1 PCM connectors, and added a set of ford 39 lb/hr injectors all at the same time. Somewhere in that process, something went wrong.

The problem:
Ever since the install we haven't been able to get the LTFTs even close to right. If we have bank 2 LTFT reading at or near 0%, bank 1 LTFT is at +25% and STFT will stay around +15%. If we add more fuel, the left side will go negative as it should, but there difference between the 2 banks stays constant. Bank 2 O2 is staying around 600-700 mv and bank 1 is in the 100-200 range if I remember right.

What I did find last time we added fuel was that after reading the plugs, cylinders 1 and 3 were lean but the rest were all a little rich. I don't know why there is a difference on cylinders 1 and 3. I have no idea what could be causing this issue.

I've talked to Mike at EFI Connections throughout the process. He's been extremely helpful throughout the process. Unfortunately at this point he's as stumped as we are. No one really has any explanation for what this car is doing.

So far, we've been through the following multiple times and have seen no change:
-All of the sensors and connectors have been checked to go to the right PCM pin
-Every wire that should have voltage has the proper voltage
-Every ground has been checked
-Every wire has been checked for continuity
-Plugs changed
-Plug wires checked with no issues
-Checked for exhaust leaks everywhere
-O2 sensors replaced
-Intake gaskets replaced
-Adjusted the rockers
-Swapped coils
-New injectors
-Leak down test and it was perfect
-Compression tested and all cylinders checked fine

At this point I can only come up with 2 possible causes that I haven't verified yet:
1)The injector wiring, being 17 years old, may have some internal breaks from being manipulated when I re-worked the harness and may not be firing the injectors properly every time.

2)The crank reluctor could have been machined wrong somehow. I'm going to check crank signal with an oscilloscope at work to verify that it is getting the proper signal. I hope this isn't the issue because EFI connections has basically told me if the reluctor is the problem, I'm basically shit out of luck and have to buy a new one (for $250).

Has anyone ever seen any issues like this with fuel trims? Does anyone have any suggestions where I can go from here?

[Ben Charles]

This will fix it
http://www.hptuners.com/forum/showthread.php?t=34714

[nskaats]

Thanks for the link. I did forget to mention, we've tried the bank assignments both ways and have seen no change. That was the first thing Mike suggested as well. This is why we're all stumped.

[Ben Charles]

Hmmm, I understand what your going through I had postive fuel trims on driverside and Negative on passenger till I set up the injector bank. I changed 02 sensors, intake gaskets, etc to find the problem, took me about 5 seconds to fix my problem by switching some 0's and 1's lol.

I would post a log on here and probably your tune so we can look at it. I am new at this too, but someone will be able to help.

[nskaats]

A friend is actually doing the tuning for me. I'll see if I can get a log file to post on here.

I understand what you're saying though and I greatly appreciate the help. We've tried the bank assignment both ways with no luck so far. I may try to experiment with this more tomorrow and see what happens.

BTW - what kind of power numbers has your combination put down?

[Ben Charles]

Yea see if your table looks like the one I posted a link too, not just the stock LS1.

Haven't dynoed my setup since I am in the tuning stage, but I would guess around 700RWHP, max reving the D1 through an auto.

[nskaats]

Out of curiosity, don't the cylinder bank assignments only affect operation in closed loop? The left side lean condition in mine is a problem in open loop and closed loop operation.

[Ben Charles]

No because injectors are firing all the time, used in both. o2 sensors are used only in closed loop, maybe thats what your thinking?

[nskaats]

That's what I thought. We had a disagreement over that

I'm going to try changing up the bank assignment tomorrow to see what happens.

[Ben Charles]

YEA man CHANGE THAT table to what my link showed. Your problem will be fixed, post a tune as well.

[nskaats]

Ok, we've tried both the LS1 and truck cylinder bank assignments and still have the exact same issues. With the truck bank assignments, the left side goes way lean and the right side is close to correct. With the LS1 bank assignments, the left side goes way lean and the right side goes way rich. I don't freaking get it.

[Ben Charles]

So your injector bank setup from top to bottom looks like this
0
1
1
0
1
0
0
1

Post a log man

[copley87blazer]

Post a log, I wold not trust the narrow band sensors. One thought though is your up pipe 02s switched diffrent sides with thw down pipe 02s.

[Fast9C1]

...added a set of ford 39 lb/hr injectors all at the same time. Somewhere in that process, something went wrong.
.
.
.
-New injectors

What jumps out at me is the unknown injectors. New doesn't necessarily mean perfect. Before I dove into the harness (which is indeed a likely culplrit), I would make sure those injectors were balanced. Not just a wide open 'how much can they flow' test, but a full sweep right down to the smallest pulse widths. It won't be cheap, but then neither was your engine.

After that, the only things that are left are the wiring and the PCM. Wiring is definitely old and I didn't take any chances with my project. I started out with a 2002 Corvette harness and used as much as possible from it...and inspected every inch of every wire and connector before allowing it on. Don't rule out that the PCM could have a quirky driver or two if the injectors and wiring are good.

[DrLoch]

As Fast9C1 suggests,1st thing I would do is have the injectors checked. He and I have have done this conversion.

Post your tune and a log.

[CalEditor@pcmcalibrators]

Have you tied turning off the dual bank fuel control?

[nskaats]

Ben, that is what my bank assignment looks like.

copley87blazer, what will that accomplish by switching the O2s?

Fast9C1, I did have one bad 39 lb injector and Ford Racing replaced that for me already. Just to be sure, I did swap to a set of 42 lb injectors and still have the same issues.

I've also tried swapping to another PCM as well. I have multiple LS1 vehicles so I used known good PCMs.

CalEditor@pcmcalibrators, I don't believe he has tried turning that off.

I'm trying to get him to post a log file on here. I really need to get this figured out ASAP.

[Badassbird]

Here is what we have. The Bank Assignments only affect trimming in Closed loop. These are Bank assignments to tell the PCM which cylinder references which O2 Bank reading. Open loop does not reference O2 voltage. Although the O2s are reading and you can see that the condition is a physically lean on one bank and rich on another not just eletrical fuzz. Here is the kicker. We pulled all the plugs on the driver side and found that 1 and 3 plugs looked close to ideal whereas cylinder 5 and 7 are very dark. 3 and 7 make some kind of diagnostic sense but 1 and 5 have nothing to do woth this swap. I have done my own 24X swap on my 94 Impala using my own brackets and factory reluctors, so I am no stranger to this swap. I just dont have, nor have I had this problem. Its very odd.

Have you tied turning off the dual bank fuel control?

No I havent tried this but being that we have a true lean/rich split what would this do for us? Please explain. Always willing to try something new.

[CalEditor@pcmcalibrators]

I will give you a call

[Ben Charles]

I am not familiar with the Dual bank fuel control?

Whats the purpose of changing that?