'03 QX4 replacement engines, JDM?

[Mike W.]

2003 QX4. 180K. Used oil since I got it 50K ago, but it's getting bad. Not quite check the gas, fill the oil but close. 6-700 per quart. Maybe. Runs great, nice interior, does need paint, killer 4WD. But it's an oil pig. I was just going to replace it with the dreaded T make, but those are just stupid expensive. And this is a known quantity. So I'm thinking about an engine replacement. Not looking for more HP or anything like that, just a lower mileage engine that isn't an oil pig.

So, after all that, I'm seeing some "Japanese" engines, which I have to assume are JDM, low mileage for reasonable price. I am in California if that makes any difference.

The obvious question is will they bolt up and run, and not set off the check engine light? I've searched, but results are thin. About all I'm seeing is 01-02 is cranky about slightly later engines. But I've got an '03. I would probably pay a guy to do the swap, I'm not afraid to get my hands dirty, but I have lost patience with laying on my back under the truck for extended periods of time. Like swapping an engine. So while I do feel he is skilled, I can't expect him to do a ton of research and changes to make it work. At least without paying him a bunch more money.

Executive summary: Is a Japanese market replacement engine a straight swap or not?

[mdmellott]

It isn't a straight forward swap between a JDM and a US market made engine. However, it is doable. The engine blocks are identical but some of the ancillary controls are different. I have found that even on my '02 PF there were changes made in the pin outs of the main wire harness to ECM connector that are not reflected in the FSM, so that's a detail to discover in a different year build swap as well. The '02 to '03 years is when the R50 models saw a switch from mechanical throttle control cables to drive by wire, and it happened mid-year in '02 on the PF in the US. That's a detail to look for also. All of these detail difference, as far as I know, can be swapped over. There are several component detail differences that need to be addressed to make the swap a success but I think it's worth the effort to keep your R50 workhorse going strong for many long years to come.

There are quite a few posts on this forum that talk about this specific JDM engine swap into the QX4 and PF. I hope these help.
engine-swap-time-vq35-check-my-pics-and-q-t588101.html
jdm-vq35de-engine-swap-t615331.html
01-pathfinder-3-5-swap-to-03-jdm-3-5-no ... 14604.html

[Mike W.]

Thanks, I did see at least a couple of the threads you referenced. Being as it's a QX4 may be an advantage as it is still a cable operated throttle, not drive by wire. It runs very well so everything would appear to be in good shape, sensors etc, it just swills oil.

So it looks like a few things have to be changed, some crossover pipe and likely the flywheel at least. That part doesn't sound terribly difficult. My friend has done lots of JDM replacement engines, so he's not new to details but may not have done one of these. Seems more Hondas and Toyotas, but I swear he does more side work than some shops do in total. He's a busy man, which is good and bad. I'd be more than happy do swap parts over, but he's going to want to go go go, it's a business to him and he wouldn't want to tie up the garage any longer than he'd have to. Laying on my back underneath it and donating blood getting things like exhaust parts loose are the parts I don't want to do,

Good, more info. Now decisions, decisions.