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Putting Series III in '04 LeSabre

10-09-2014, 09:14 PM
So I've seen evidence of the swop being done successfully on other vehicles! I've got a line on a Series 3 motor (and trans?) that I want to put in my Series 2 '04 LeSabre. Physically I know it's the same engine but the first thing I notice, other that the very published stuff, is top engine mounts('04 GrandPrix). Can the lower mounts be transferred from Series 2? I will still use the throttle body(adapter plate) and fuel rail from the LeSabre because of the differences. Will use existing trans. I'd like to pull motor only, from the top. Any advice? Does the motor release from the trans with enough room to go up? I've pulled tranny before from bottom but never the engine. Is it better to drop the cradle? Kinda excited to lose the plastic plenum! Oh, the reason to replace is low compression in cyl. 3...75psi. Can't seem to get rid of that rough idle!...So, unless somebody has other ideas, I'm replacing. What am I missing? Should I NOT bother with a Series 3 for an '04 LeSabre?

11-02-2014, 07:58 PM
Lot of views but no opinions? Well, I finished her up today. This was a swap that used the existing S2 wiring and PCM. Was just looking to never have to do the plenum again.

It can be done but there are a few changes that you will have to address.

Mounting brackets and parts have to be swapped from your S2 to the S3. That includes;

AC bracket, power steering bracket, rear exhaust manifold, oil pan and oil pickup tube, oil filter mount, engine mount, fuel rail and injectors. You must use the S2 alternator. Throttle body needs an adapter to the newer plenum. This creates the biggest problem because this setup takes up more real estate...


The air box has to go because the throttle body is now too close. This exposes the PCM. I used an aftermarket hose and cone air filter, which ended up in the fender well. I just cut the air box's top off, leaving the mounting grommets, which left just enough room for the 4" hose to get to the existing hole(where the old cold air came from) above the naked PCM in it's old spot.

You'll need to extend the vaccum lines 2" and plug a couple other ports on the plenum. The wires to the sensors on the throttle body are a little tight. I made them work and didn't extend any wiring. Drilled a 1/2" hole in the new air hose for the intake temp sensor.


If you're just pulling the engine you'll need to get to the "B-bolt" to the trans. from the right side with extensions. I suggest taking the motor mount off and out of the way. I struggled until I took this part off. Once off you can see the bolt and have direct access from the wheel well....easy!! Well, once you have the right side motor to trans bracket off. I would buy taps to fit the ground bolts(10mx1.5) and the upper stud for the motor mount(not sure of the size). These "holes" aren't used on the S3 and mine needed cleaned up because of rust. I used the bolt as a tap and almost blew it on the top ground by the ICM.

This was the first time I've replaced a motor and I think it went well. Fired right up and no CEL/SES. Now I have a 78k motor installed, which, of course, means it will still likely outlast the car. Just like all of my 3.8s have. But no more plenum replacement!

Just in case anybody was wondering!

11-03-2014, 12:39 AM
Glad you got it working. I could imagine when you finished, getting ready to start the motor to see what will happen.

Just curious, what happened to the original engine?


11-03-2014, 09:08 AM
My girlfriend had this car break down on the E-way. "Lost all power. Heard a thumping noise. Thought I was gonna die!" Had it towed home. Fired it up. Rough idle. P300 random misfires code. Threw parts at it, coils, plugs. THEN I checked for spark! DUH! Fuel pressure OK. Pulled plug on individual injectors while idling. Cyl 3 showed no change. Noid light test was OK. Got a couple injectors from JY and same result. Car ran fine above idle. No knocks or metal noises at all. This was done while on a week off from work! Other projects still todo. Out of time, I gave up and took it to local mechanic. "Low compression in Cyl 3. New/rebuild motor." Saw this motor on CL and jumped on it. $600 motor and trans with 78k miles. Should get some back for trans, alternator, and throttle body.

I wouldn't hesitate to put a Series 3 in for a 2 again. But it would have been easier and looked cleaner if I had just put in a Series 2. JY wanted over $1k for same milage Series 2.

11-08-2014, 11:15 PM
Thanks for posting this.

Yeah, there aren't many Series II's with less than 100k on them around anymore.

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