3500 Swap Into a '03 Grand Am

[anelsen]

Hey guys I migrated here from GA owners club since no one there has done what I'm trying to do. First off I appreciate any help anyone can give me, even if it's a small tip. Well here's the problem: I'm swapping my old engine out of my '03 GA for a '06 lx9. After a bit of consideration, I'm seriously thinking of using the uim on the lx9 instead of using the old 3400. Basically, the only parts I would retain is the fuel rail and injectors from the 3400. I've heard the increased mpgs range from 3-7 from using the new uim, Is this true? I know I will need a 2005-2006 pcm for the electronic throttle control, crank sensor (so I don't have to use the external), and probably a few other things. I'm guessing this means I will also need the wiring harness. I believe the old BCM should be fine with the new pcm right? Is there anything else I need that I don't realize? And is there any good reason not to pull the pcm from a junkyard? Thanks for all the help guys, I really appreciate it!

[MY91GT(Z)]

you dont need to swap out any harness you can get lx5 tb adaptor and get a 65mm tb off 3.5 intrigue to save the hassle and you will also need crank trigger also. and no you wont see that big of difference in mpg from just uim. and if you really want to save money at the moment you can put your 3400 uim on and drive it w/o issues also. good luck and enjoy new found powa

[bszopi]

Trying to use the '06 PCM is going to be a pain, and I doubt your '03 BCM will work. Although not positive, I am pretty sure that the newer PCMs use CAN protocol for communication between devices, which your existing BCM does not. If you did try to use the new PCM (not sure why you would want to maintain DBW throttle control), you would need all the parts for the DBW, which would include the pedal and the control unit at the engine. It would be much easier and cheaper in the end to use the 3400 UIM, or if using the 3500 UIM, then getting the LX5 adapter as mentioned above, or a new throttle body, as well as the external crank trigger.

[anelsen]

Thanks for the input guys. I will probably stick with the 3400 uim and old pcm for now, and save the 3500 uim for an upgrade later. I've already got the external crank trigger, but I don't really want to spend another $50 on the throttle body adapter. I'm a college student so I'm cheap . Thanks for the help!

[bszopi]

Going that route will save you time, money, and headaches.