New project! 8746 ECM swap into the LU5 Crossfire Trans Am 

I just figured it was a good idea to finally do the swap. I drive this car so much, if the 6026 ever goes out, the car is literally dead in the water. I’m looking forward to seeing how the 8746 runs, and what kind of improvements it gives in terms of fuel economy and overall driveability.

The ECM I’m using is an 8746 from an 89 L03 Caprice. The trucks use a 7747. The difference is the 8746 used an IAT and has lean cruise mode enabled. The 7747 doesn’t. The 82-83 Trans Ams do have a functional air induction unit, but the solenoid is adjustable, so I adjusted it so the internal flap is always open. It can be wired up like an LG4/L69 Trans Am by using a vacuum switch, which I may do down the road. As far as the 8746 in my 83; it runs leaps and bounds better than it did with the 6026. It runs smoother, is much more responsive, and the gas mileage is better by a landslide. The ECMs that can be used are the 88-93ish 7747 out of a C/K truck, and the 8746 out of the 89-90ish Caprice/Impala. The F-body 8746 will work as well, but has VATS enabled, so you would have to work that out.

Are you in AZ?

@@Joesmusclecargarage ya, my uncle lives in Yuma

The HAM/EBL is fine, just expensive for a simple ECM swap. I don’t mind sitting on the ground a couple of hours a day for a few days to do the wiring. The way I see it; if you do the HAM board and something happens to the ECM down the road, or want to change it, that’s money out the window. The EBL is great for serious modifications and tuning though.

@@Joesmusclecargarage That's true too. I think I had asked bob (EBL) when I was having fan issues and he said it would be able to be pulled and resoldered though... But let's hope I don't cross that bridge in my lifetime and all is good lol. Mine has enough going on that it made sense to go with it though as I'm sure you've seen. My big thing with the wiring is I don't fit... I did the heater core when I was 12. Know for sure I can't get under the dash... which is much easier in a thirdgen than a C4. However like I said, you do end up with a more useable end product swapping to the new harness. I probably would do it different if I were starting over and make an entire new harness myself just for the simple fact the car is almost 40 years old and on factory wiring.

@@ratherbeboating10 All good. There’s no right or wrong way to do something if the end result is the same. I know most people HATE wiring. I myself find it relaxing and sometimes enjoyable; building a nice clean harness from scratch with factory style connectors/pigtails, diagnosing, etc. Then again, I do it all, from engine/transmission/diff builds, to show quality body and paint. Mentally, wiring is a walk in the park compared to guiding and blocking a car for months in end, lol. How does yours run after the ECM swap? Any improvement over the original 6026?

@@Joesmusclecargarage actually never ran the 6026 with the heads and cam. Did run it with the renegade and mild cam. It ran a lot better even than stock with it. It always ran well, but idle down (approaching lights) and low speed behavior (parking lot type stuff) improved. But wide open didn't seem any better. I also enjoy wiring. I did a lot on a 67 firebird and altered quite a bit of the stock wiring to work with what was done to it. Granted that whole harness was maybe half a modern one but was still fun. I am nervous now as the plastics on all my connectors are getting brittle. I've replaced a couple like the MAP and TPS ends but I worry about the injector drivers and distributor wiring. Last I checked the distributor parts are NLA and the knock module too. If all that starts going I'll probably pull the engine and work on a custom wiring harness/solution. but for now it is perfectly fine in my imagination lol.

As far as the IACs, the two IACs on a Crossfire are wired parallel. Both of the IACs receive the exact same signal from the ECM. They don’t work independent from each other. The wiring is basically identical to a later single TB 305/350. You still have two injectors on both styles of TBI, a “left” and a “right”. As far as the 12-pin ALDL, it too is identical to the later cars as far as how it’s wired. The later OBD2 port wasn’t introduced until 1995 on some OB1 cars, and 1996 across the line. If you were to compare a 1982 ALDL port to a 1989, you’ll find the wiring is identical. Like I said, I’m all for the EBL/HAM, but what happens when you need/want to replace the ECM after spending all of that money on an EBL/HAM? It doesn’t just “transfer” over to a different ECM. I figured for a stock/mild car, the way I’m doing it makes it totally plug and play, and completely eliminates the unreliable “card edge” ECM connections for good. With a HAM board, you’re still stuck with inferior 1982 ECM plugs. 👍

A bad ECM could very well cause what’s happening. Have you verified fuel pressure? Does it run fat in open loop, closed loop, or both? A very common culprit is the CTS on the front of the intake, right above the timing cover. They were junk when they were new and a popular upgrade is a CTS from a late 80s 305 Camaro. A new sensor with the upgraded weatherpack pigtail is about $20. Check timing, and verify the vacuum line to the MAP is in good condition.

@@Joesmusclecargarage hello Joe, thank you for a answering my question so quickly. I have not verified the fuel pressure yet but it seems to run fat in open loop. I feel like it never goes into closed loop. After a couple minutes the injectors start to sputter and than in stalls. After I have to disconnect the Injectors and start the car to get rid of the extra fuel and start the process all over. I also changed the CTS sensor.

You are correct. The ECM operates on preset parameters until the engine warms up and goes into closed loop. Once in closed loop, the ECM receives input from the O2 sensor to maintain a 14.73 to 1 air/fuel ratio. As far as your 84 running rough during open loop operation; what have you done as far as any kind of tuning to the car? Have you verified the correct fuel pressure? Stock CFI runs “best” at around 13-14psi. TPS should be set @ .525V AFTER correct synchronization of the throttle bodies. Fuel atomization and distribution isn’t the best with these manifolds, and they’re known to run a little “rough” until they warm up. There were TSBs from back in the day concerning cold start/running operation. They run beautifully when they’re warmed up a little bit. But every CFI car I’ve had was a little rough on cold starts. I think it’s just the nature of the design of the manifold.

@@Joesmusclecargarage Thanks for all the info. When I first got the car I had a problem where it would be very hard to keep running after a hot start. I calibrated the TPS, and I also changed the fuel pump to an 85 model. It seems to have helped the problem. I have NOT synced the throttle bodies yet. I probably should do that. I'll take a look at your video on that topic again. Back to the fuel pump - I know the fuel pressure regulator is pre-set (I think) but I believe the extra fuel flowing to the TBIs help to keep the engine from stalling when hot. Thoughts?

You can swap in the 8746 but it will not run well, just as the current 6026 more than likely runs poorly with the factory LU5 PROM. There is no such thing as a “stage 2 cam”. The exact specs are needed, but for any 350 swap into an LU5 car, a 350 PROM is needed, whether using a 1982 5055 ECM, 1983-1984 6026 ECM, or a 7747/8746 ECM. With a 305 PROM, a 350 will run lean, idle poorly, and will severely lack power.

@@Joesmusclecargarage I used an Enginetech rebuild kit and they referred to the CAM included as a "Stage 2 high performance". I guess that's just for their use. Thanks for the quick response!

@@justincase6151 Just be careful to keep you intake duration @.050” under 204, and your LSA 112-115, or you’ll need to do some PROM burning/tuning.

@@Joesmusclecargarage my intake duration rating @.50" is 214 and my LSA is 112. Looks like a prom burn is in order. I found an ECM on rock auto for the '89 Caprice 350 5.7 engine which seems to include the appropriate prom. Thank you!

@@justincase6151 No reman ECMs are supplied with PROMs. 7747/8746 ECMs are super common. It’s getting ahold of a compatible PROM that can prove to be difficult. I just sold a NOS L05 PROM for an 8746, so they’re still out there. Anything L05 will be pretty difficult to find though.

Nope. Got rid of it 2 days after I fired it up with the 8746.

@@Joesmusclecargarage ok, so I'm going to have to do the 8746 conversion.😔 It's a bit more difficult for me though, because I'm in South Africa, that's why I was just looking for the original but I hear what you said about availability etc. Thanks for the reply, appreciate it 👍

The wiring is identical from 82-84

Thanks I appreciate you sharing your knowledge.

The 82 Corvette and Camaro/TA use the 5055 ECM, and the 83 Camaro/TA and Corvette use the 6026. You can use a 5055 from an LU5 in your 82, but you’ll need to use the L83 PROM. The 6026 is also plug and play, but we’re only available with the LU5 in the F-bodies. In order to use a 6026, you’ll need an 84 L83 PROM from a Corvette. Or do like I did, swap in a 7747 or 8746 and use an L05 PROM.

Yes. The 7730 is a MPFI ECM and will not work with the LU5/L83/L03/L05.

@@Joesmusclecargarage thanks for the info! So my only options is a 7747 or the 8746?

@@chrisfayling For the most part, yes. Those are the popular ECMs used for swaps. The 7747 is a truck/van ECM, while the 8746 was used in F&B bodies. The 88-92 F-bodies used VATS, the B-bodies did not. VATS is programmed into the PROM, not the ECM.

I said that because they matched on the pigtails I used. Only 2 or 3 of the wires were a different color. Either way, I can’t imagine it was that difficult for you to figure out.

@@Joesmusclecargarage What pigtails did you use?

@@Joesmusclecargarage Out of what did you get your pigtails? I want to change my ecm and I want the pigtails you used so I don’t have any color matching issues and can you also send me the diagrams you used?

Of course. I’ll send you the wiring diagrams. What’s your email address?

@@Joesmusclecargarage hi Joe, did you receive my message with my email address as the message is not showing up on my account, please let me know if I have to resend it, thanks Darren

Are you ignoring my messages for any reason, have I offended you by offering you some money for your time n trouble?,

How old are the pump and filter? Have you checked/replaced the ECT sensor?

When I had purchased the car in February the guy told me he just replace the fuel pump. The service engine light was on I have a code 22 and a code 42 Replace control module and distributor, throttle positioning sensor.

Not sure where to find that I have a gm shop manual

Email me at roccojakubec@yahoo.com and I’ll scan the flow charts in my 82 FSM for codes 22 and 42.

Yes. I’m not sure why you would want to though. The 5055 is ridiculously inferior to the 7747/8746, and uses a one year only knock sensor and ESC module, as well as the horrible card edge connector. People pay $250-300 for the 5055 in working condition. You’d be better off selling it and grabbing a 7747/8746 for $50.

@@Joesmusclecargarage What other changes / upgrades would you do to a bone stock crossfire car to make it responsive, good acceleration, and run a lot better? In your experience while keeping it crossfire

@@robinlovescars Bump the timing, bump the fuel pressure, headers and exhaust, etc. The typical stuff. You can’t do much to increase the “response” of a CFI car. The ECM is only so fast. You can only optimize what is already there.

@@Joesmusclecargarage Would you recommend removing emissions equipment as well?

No. None of the emissions equipment reduces performance, other than the factory cat if it’s still there. As a matter of fact, keeping the EGR lowers combustion chamber temp, allowing for more timing and better fuel economy. Ideally, the EGR command should be removed from the PROM if the valve is deleted. The ECM adds timing when the EGR is commanded. As far as the A.I.R. pump, it’s only a 2-4 horse drag. Nothing you’ll ever feel, or even see on a time slip. All you’ll accomplish is having a “hacked” engine compartment.

The 8746 will absolutely work in place of the 1982 5055. You will need an L05 PROM. An easier ECM to find would be a 7747 out of an L05 truck. Basically the same ECM as an 8746, but without the IAT.

7747 doesn’t have the VATS either? 7747 is just a run of the mill 5.7 TBI truck ecm? Minus the lean cruise mode?

@@mattodonnell9182 Correct. No VATS with a 7747. The lean cruise mode can be enabled on a 7747, it just isn’t in factory configuration. I only suggested the 7747 because it’s a much easier ECM to get ahold of with a 350 PROM. With an 8746, you’re pretty much limited to 89-91 Caprice/Impala.

@@Joesmusclecargarage haha, I threw one away a few years ago when I put a 11.1 350 with AFR heads and a big roller cam in a 1990 c1500 sport that had a cracked block 350tbi in it. Hindsight is 20/20 right!🤣 that was a fun truck though. Ran 12.70’s blowing the Hoosier DOT slicks off it at the now defunct Atlanta Dragway. I am not looking for that kind of performance out of my vette, just looking to improve drive ability and performance. It runs good now, knocks out low to mid 20 mpgs with the abysmal 2.83 gears in it. Idles rough though, high idle hangs until you come to a stop and let it come down, and I am getting ready to port the stock intake and throw a set of 3.73’s in the back. Hoping an ecm upgrade will be just what the doctor ordered. Later I am probably going to go throw a set of aluminum heads and small roller cam in it. Your videos are inspirational since I want to see how much I can improve the factory crossfire system. I feel based on yours and other folks builds I can get this from a sleepy 16 sec car to a respectable low 14 high 13 car retaining or actually improving its drivability manners. It’s a challenge I am looking forward to and you have certainly paved the way with great information and knowledge.

Of course. My 83 has a 700R4. The ECM doesn’t know or care what trans is in it. All the ECM does is activate lockup.

@@Joesmusclecargarage when you ported you're intake did you have any problems with fuel puddling in the intake. The engine is not happy till 2800 rpm's. 82 vette aluminium head's an 1.6 rockers just like you.

@@10rrace When I pulled the top plate off to swap to a single TBI manifold last week, I had a small amount of fuel puddled in the CFI base. This is something that was not there before I ported the base. That is the reason they designed the manifold the way they did, with extremely small runners. The engineers had the exact problem with fuel puddling at low RPM. Their solution was to reduce the overall volume of the runners to increase port velocity and maintain fuel atomization, which in turn gave very good bottom end and decent midrange, but made the motor a pig at high RPM. There’s really no way around it. People have ported these manifolds every way possible. The end result is more than likely the same.

Do you think the new ECM will help by managing the fuel better? Thanks Nick

@@10rrace It will help, especially in open loop.