dmac1968

I am looking for guidance on which way to go with this swap. I have a built 1994 LT1 that is an LT4 conversion 383 stroker. It has LT1/LT4 Hot cam, LT4 heads and MSD Part #8381 Kit on it. I am wanting to know if I should convert the engine to OBD2 or convert the OBD2 to OBD1 in the 1996. Which one is easier or the best option? The 1996 is an m6 car and the 1994 is an A4. I am switching to m6 when i do the swap. The 1996 is a roller car which the harness was left but ecm is gone. Also if I covert the engine to OBD2 wont i have to buy all new MSD igniton parts? Any help or guidance would be greatly appreciated! Thank you in advance!

Injuneer

The MSD Opti itself (not the coil) is compatible with both OBD-1 and OBD-2. Electrically, both are identical, except for the harness connector. And if the MSD has the permanently attached harness, even that problem goes away. The only real difference is mechanical in that the drive mechanism is different - splined shaft vs. cam dowel pin.

If by "#8381 Kit" you mean you bought the 8381 distributor with the MSD coil and MSD 6AL box, you will have to tweak the harness wiring to the coil, since your 94 has a dual-connector coil, and the 96 harness is set up for a single-connector coil.

Shoebox has the wiring diagrams for 94/95 and 96/97 for you to compare:

94/95
http://shbox.com/1/95_ign_system_schematic.jpg

96/97
http://shbox.com/1/1996_ec_03_ign_system.jpg

Unfortunately, GM used a format change in the presentation from one to the other, but you just need to trace the connections to the coil. If you need help with that, we can advise.

Since the 96 PCM is missing, but the 96 still has the 96 harness, just use your 94 PCM. It is still plug-and-play. Stay with OBD-1.... better scan software and programming software available. Fewer invasive diagnostics.

You will have to have the 94 PCM reprogrammed with an M6 program.

The only differences between OBD-1 and OBD-2 are:

- the use of a crank position sensor on OBD-2 for misfire detection. You won't miss that, since you don't have it now. Just leave the CKP sensor harness connector on the 96 harness unconnected.

- vacuum detection switch on the OBD-2 EVAP system, located on passenger valve cover. Again, you don't need it, won't miss it, leave harness connector unconnected.

- after-cat O2 sensors on OBD-2. You don't want or need those. Leave harness connectors unconected.

- If you were to buy a 96 PCM and use it, you would have to swap your 94 knock sensor (4 Kohm) with a 96/97 knock sensor (100 Kohm). Sticking with the 94 PCM avoids that.

dmac1968

Yes, the #8381 kit I have has the Opti, Coil and Box. Can I just purchase the single wire coil to resolve the issue vs rewiring? As for having the PCM reprogrammed with the M6 program is that something easy I can tune myself if I have the software or would you recommend sending it out? Also for the cam position, Evap sensor and 02 sensors -will these need tuned out as well to prevent the CEL from coming on or will the OBD1 PCM just not pick them up? If this is easy is there software, connectors and tune kits you can recommend or if its better left to the professionals is there anyone you recommend? I am in the KC area but would also be willing to send it out, I appreciate you providing the in depth advise. This is more than helpful!

Injuneer

You should be able to switch to the single connector coil, but you will probably need an MSD one-connector adapter harness to connect it to the 96 harness.

My suggestion is to use your current OBD-1 94 PCM. The 96 harness connectors will plug right into it with no changes. Since your OBD-1 PCM has no provisions for a CRANK position sensor, the EVAP vacuum detection switch, or the after-cat O2 sensors, there is no requirement to "tune them out". And only OBD-2 sets codes for those systems. Since they do not exist in OBD-1, there is nothing in your PCM to receive info from the sensors, and no diagnostics to determine if they are connected. Leave thesensor harness connector loose, tape it up, or cut it off and tape it up, and tie the wires out of the way.

I can't give you a definitive answer on the M6 program. I BELIEVE it requires a complete reflash, not just weeks of individual tables. A professional tuner would extract your current tune, obviously custom for the cam and displacement changes, and include that tune with the new M6 flash, and make any adjustments to your engine tune for the trans change. Reliable mail-order tuners are becoming harder to find. I replaced my stock PCM with an open architecture, high end engine management system 17 years ago. My stock PCM tuning experience was limited to minor tweaks using LT1_Edit software. Never faced an issue with a trans type swap.

This tuning guide gives you info on software available for scanning (not updated for addition of Scan9495, and deletion of TTS DataMaster), software for tuning (not updated for LT1_Edit no longer available), and the required cables.

http://www.lt1pcmtuning.com/tips/

Note that with keeping the 96 wiring harness, you will have an OBD-2 16-pin diagnostic connector under the dash. You can keep the 16-pin connector, and get an OBD-1 16-pin connector cable (the 95 needs it). Then just make sure the diagnostic data wire is in the correct pin position (9), and any other wires that are not required are removed.

Use Shoebox's wiring diagrams as a guide:

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