Topic: '97 2.5 in a '93 YJ

[Kman]

I checked the FAQ and have searched but can't find an answer to what I'm looking for. We just bought a '97 TJ 2.5 engine to replace the engine in my wifes '93 YJ. My original plan was to simply swap the '93 dist, intake and sensors(OBD I) onto the '97 engine(OBD II). After picking up the '97 TJ 2.5 I really like the power steering pump mount and the easy accessability to the adjuster bolt. Can I just mount the '93 throttle body onto the '97 intake? Also are the OBD I and OBD II flywheels the same? I also ordered a 9 LB inertia ring from Tri County Gear to put on before I put the engine back in. My wife is running 4.88 gears and 34x10.50 Swampers so I think the inertia ring will help. Thanks, I'm not very familiar with the OBD II stuff.

[sharpxmen]

i think the waterpump spins backwards compared to the '93 - so pay attention to that. if you have a mechanical fan then you need to replace the pump and if you can route the belt over the new steering pump then i don't see why you wouldn't be able to keep it. you can bolt the t/b but you'll need to tee off some other vac line to the MAP sensor, although i would join other vac lines and would keep the MAP straight to the manifold. If you do end up using a T to connect the MAP make sure it's not a line with a check valve on it.

on the '97 cyl head you are missing the temp sensor (close to the firewall). It's not drilled although it's the same cyl head.

Not sure about the flywheel, i think it's the same but not sure, better check.

[Bounty Hunter]

Sharp, IIRC the XJ/MJ 2.5L water pumps spin opposite the TJ/YJ engines, is that what you're thinking of?

You can use the '97 throttle body if you change any sensors that have plugs differing from your '93, and cap the vacuum port to the MAP mounted to the base of the TB.

You will want to reuse the YJ fueling system, it's the largest difference between those two motors.

[sharpxmen]

Sharp, IIRC the XJ/MJ 2.5L water pumps spin opposite the TJ/YJ engines, is that what you're thinking of?

maybe i got mixed up, I thought TJ waterpump spins opposite to YJ and has different serpentine routing - now that you mentioned it maybe i got it wrong.

you're right about the fuel system, he'll need the injectors and injector rail from the YJ as well

[Kman]

Thanks guys! The '97 came with all the front accessories including the fan. I will probably drill and tap the head for the temp sensor. The injectors and rail shouldn't be a problem to swap over. I'm doing some searching for flywheel part numbers to see if they are the same, no luck yet but I'm still looking.

[Kman]

Went to Rock Auto's website. It lists the same part numbers for both the water pump and flywheel for the '97 and '93 2.5's!

[Kman]

Turns out the head was drilled and tapped already and just had a plug in the spot where the YJ temp sender will go. The intake also has all the vacuum ports I need. There was 1 port on the TJ intake that was simply capped off so this is where the MAP will connect. I swapped the '93 fuel rail and injectors over to the '97 intake. I just cleaned up a '93 4.0 throttle body to drop on. So far so good!!

[Kman]

Well I got it fired up today and it sounds good. I ended up swapping on a 4.0 throttle body as described on this forum. I used the '97 intake manifold  and swapped on the '93 fuel injectors and rail, distributor, coil, and sensors. I used the '93 flywheel and added the 9 lb inertia ring from Tri-County Gear while it was out.

[MarkyB]

Since I'm gonna be swapping transmissions, would an inertia ring be something to consider with an auto?

[sharpxmen]

Since I'm gonna be swapping transmissions, would an inertia ring be something to consider with an auto?

you don't need it with an auto, it won't stall on you as it would with the manual transmission (that's what is for).

[MarkyB]

I was hoping it would negate some of the drag caused by the A/C compressor.

[sharpxmen]

I was hoping it would negate some of the drag caused by the A/C compressor.

i'm confused, what do you exactly mean? is it stalling when you turn on the A/C?

Not sure if I understand the matter correctly but if stalling when using the A/C is not the issue and you're referring to the power consumed by the A/C then the only way to not have the "drag" from it is to turn it off. You'll always have lower mpg when you add consumers to the system (stereo, headlights, a/c, etc) - they all use energy and that is provided by the engine, a/c is a bit more thirsty, but even with just the heating fan on for example it's still something that uses electricity and in turn the alternator will consume energy from the engine. Unfortunately there's no free power and the inertia ring will actually consume some as well and will not provide any, the only purpose of it is to add rotating mass to the crank and increase the rotational inertia of the assembly (like the name says) - by doing that it makes it harder to stall (stop rotating), however it uses more energy to bring it to a higher rpm, so during city driving for example when you go from stand still a lot will lower your mpg.