97 4.0 in a 99

[UBU0550]

Hey all, trying to help my brother out. He was in an accident in his 99 TJ a couple years back, wrecked the motor, and it was pulled out and sold. We came across a 97 for cheap, and swapped the motor, but as you all probably knew more than we did, that a lot of the connectors from the 97 motor to the 99 wiring harness don't match up. He's strapped for cash, so I'm trying to surprise him and buy as much of the parts that need to be swapped on the motor for him, but I'm trying to crowdsource knowledge from y'all on what parts and sensors I will need to order for him. Any help would be appreciated. I'll add to the list as I get info from y'all. So far I know the injectors are different, the plug for the distributor is different, connectors for the starter and alternator seem different as well.

Edit: sorry I wasn't clear, the original motor is no longer available, someone bought it after the accident.

 

[Sea Cot]

Just to be clear, your '99 has a distributor instead of the coil-on-rail ignition system, right? During '99/'00 was when Wrangler converted from distributor to COR.

I went the opposite direction of you when I swapped a '99 distributor engine in to my '98.

I'd strip the '97 to a long block and move the '99's complete intake, exhaust, AC compressor, alternator, AC and alternator brackets, and the oil pressure sensor. I don't recall what, if anything, had to be drilled or tapped on the block to make it work.

 

[machoheadgames]

The engines themselves should be the same for those years. Just move all the external parts from the 99 engine over to the 97 engine.

 

[UBU0550]

The engines themselves should be the same for those years. Just move all the external parts from the 99 engine over to the 97 engine.

That would have been easy, but he sold the motor out of his after the accident. He was originally planning on going in a different direction with the new motor, so we don't have the original motor for reference.

 

[UBU0550]

Just to be clear, your '99 has a distributor instead of the coil-on-rail ignition system, right? During '99/'00 was when Wrangler converted from distributor to COR.

I went the opposite direction of you when I swapped a '99 distributor engine in to my '98.

I'd strip the '97 to a long block and move the '99's complete intake, exhaust, AC compressor, alternator, AC and alternator brackets, and the oil pressure sensor. I don't recall what, if anything, had to be drilled or tapped on the block to make it work.

I'll edit my original post, I wasn't very clear. The motor was pulled and sold after the accident, luckily all the wiring harness was there, just no old motor to reference. And the PCM is MIA also, but that's a problem for another day.

 

[machoheadgames]

That would have been easy, but he sold the motor out of his after the accident. He was originally planning on going in a different direction with the new motor, so we don't have the original motor for reference.

Ah. Didn't think of that. Any chance you could tell us which ones aren't plugging in? It's tricky because ones that changed, changed at random times. Off the top of my head (and I may misremember some):

• The ignition coil was new for 98-99
• MAP sensor was the same for 97+
• Distributor pickup coil (also called cam position sensor or fuel sync sensor) changed for 1998-1999 (distributor gone in 2000)
• Coolant temp sensor was same for 97+
• Throttle position sensor (TPS) was the same for 97+
• Idle air control (IAC) changed for 98-04
• Intake air temp (IAT) or air intake charge temp sensor was the same for 97-04

It also might matter if this 97 engine is from an early or a late 97. The early 97s reused YJ sensors on a few of them (likely the ones that became 97+ in the list above), like the TPS, IAT, and some others. So take a look at some photos online of the 97+ sensors (the ones you may not have to buy) and make sure the ones on the engine you got match what the online 97+ look like, so that you aren't battling trying to plug into an early 97 and older version that would actually be a YJ sensor.

When the original 99 engine was pulled and sold, did the wiring go with it? Does the 97 engine have any wiring on it or it's bare with just sensors and you're trying to plug them into the 99 harness?

 

[UBU0550]

Ah. Didn't think of that. Any chance you could tell us which ones aren't plugging in? It's tricky because ones that changed, changed at random times. Off the top of my head (and I may misremember some):

• The ignition coil was new for 98-99
• MAP sensor was the same for 97+
• Distributor pickup coil (also called cam position sensor or fuel sync sensor) changed for 1998-1999 (distributor gone in 2000)
• Coolant temp sensor was same for 97+
• Throttle position sensor (TPS) was the same for 97+
• Idle air control (IAC) changed for 98-04
• Intake air temp (IAT) or air intake charge temp sensor was the same for 97-04

It also might matter if this 97 engine is from an early or a late 97. The early 97s reused YJ sensors on a few of them (likely the ones that became 97+ in the list above), like the TPS, IAT, and some others. So take a look at some photos online of the 97+ sensors (the ones you may not have to buy) and make sure the ones on the engine you got match what the online 97+ look like, so that you aren't battling trying to plug into an early 97 and older version that would actually be a YJ sensor.

When the original 99 engine was pulled and sold, did the wiring go with it? Does the 97 engine have any wiring on it or it's bare with just sensors and you're trying to plug them into the 99 harness?

So so far the things I know are different follows.

Injectors (got a new fuel rail too, it was a little rough on the donor)
Starter
Alternator
Distributor
Oil Pressure Sensor

Thanks for the IAC, I'll add that to the list.

The donor was a late 97, so I think ended up a little lucky there. The donor was a mostly complete jeep, so had the entire wiring harness and everything, and his 99 has the entire harness intact, nothing was cut except the fuel line.

 

[Rickyd]

So so far the things I know are different follows.

Injectors (got a new fuel rail too, it was a little rough on the donor)
Starter
Alternator
Distributor
Oil Pressure Sensor

Thanks for the IAC, I'll add that to the list.

The donor was a late 97, so I think ended up a little lucky there. The donor was a mostly complete jeep, so had the entire wiring harness and everything, and his 99 has the entire harness intact, nothing was cut except the fuel line.

Is the donor available? I'd be tempted to just set this jeep up as a 97 with its pcm,cluster etc

Btw you can find wiring diagrams in the resources section here

 

[UBU0550]

Is the donor available? I'd be tempted to just set this jeep up as a 97 with its pcm,cluster etc

Btw you can find wiring diagrams in the resources section here

The doner is still around, going to be throwing it on the marketplace here soon to see if there's any parts someone else can use. In regards to turning his 99 into a 97, this started out as what was supposed to be a quick and easy way to get his jeep back on the road. And we're trying to still do that, and I think changing the parts to a 99 is still probably easier than swapping the engine harnesses and PCMs. Though right now we're going to try and use the 97 PCM, until he finds wherever he put the 99. We're going to see if it works, at least.

 

[hear]

My thought is that if the jeep was a 99, then your harness is going to be a 99, which is going to make you want to keep on treating it like a 99 in terms of sensors, ignition, etc.

But if you don't have the 99 PCM, then expect some headaches. Swapping the harness in won't be a direct swap either, I briefly tried to put a 98 or 99 into my 97 and saw that the firewall connections were different, so I abandoned that. Macho gave good info on the sensors, but I'll add that SOME early TJs have a 2 wire oil pressure sensor that I've never found documented in the FSM. You can hack the wiring to make it work, but it's going to be easier to just get a sender that matches your harness.

 

[UBU0550]

I agree with you, we are treating it like a 99, and will purchase everything to make that wiring harness work. In regards to the PCM, if there are too many headaches with the 97, or issues, if he can't find the PCM I'll find a used one somewhere. Definitely trying to minimize any splicing or mods to the wiring harness.

 

[hear]

wranglerfix.com is your best bet for the PCM.