I've been trying to help a friend of mine diagnose his '04 G35 for the a while now, and we finally got back to it today after he installed the correct spark plugs. Long story short, the old motor began knocking and he dropped in another. He mistakenly bought those awful E3 spark plugs and it was running HORRIBLY. The car is essentially straight piped, and the exhaust was popping every few second because of the outrageous amount of fuel getting to the exhaust.
We reconvened today after he installed the proper NGK plugs, and while the car is running better, it's still not perfect. It's idling very rough, and the bank 2 upstream O2 sensor is sitting right around 0.9-1.01V. Fuel trims are pegged at 25, and I'll occasionally see them drop as low as 18. All 6 plugs look fine, but cylinder 1 seems to be a little wet, I'm assuming with fuel. I swapped the coil to another cylinder, no difference. I'm not ruling out a sticky injector yet, but I'm not going to focus on that. Obviously being on bank 1, I don't know why that would cause bank 2 to be running so insanely rich.
The B1S1 O2 sensor is running around 0.5V, so that seems to be just fine.

The only code showing is P0300, but from what I understand, these Nissans typically only show a random misfire rather than a cylinder-specific misfire.

I have not yet checked fuel pressure or compression, but it's on the list. I'm thinking that the culprit is on bank 2, however the fuel trims are equally high on both banks. Seems strange to me being that bank 2 is the side that is showing the high O2S voltage, but I guess anything's possible.
I did also try unplugging the MAF to run it on base maps, that made it run far worse.

Does anybody have any ideas here?

 

Typically when you motor swap you keep all the existing sensors, injectors, throttle body, coil packs, etc.

That helps rule out other potential issues, I recommend putting all the original stuff back on this donor motor, especially the injectors and cam/crank sensor.

Also just to verify, the flywheel/flexplate did get properly aligned on the dowel pin on the back of the crankshaft yes?

 

I would love to say that all of that was done, but unfortunately he sold the old engine pretty quickly. I told him not to for this specific reason, but he already had a buyer. That said, I believe the engine came from an '05 sedan. I'm not TOO experienced with these cars, but from what I understand, the '05 sedan should be the same as the '04 coupe.
The flywheel should have been installed correctly.

Initially I had thought that the injectors could be an issue (perhaps they still are) because Infiniti switched between Bosch and JECS injectors midway through 2004. His car is a late 2003 production date, and I believe should have had the JECS injectors. I'd love to be able to confirm this with the old motor, but like I said, that's long gone. The car currently has Bosch injectors. I haven't been able to find a clear answer on whether they are interchangeable, but I'm assuming they're not.

Like I said, it's running significantly better now that it has the correct plugs, but it's still not right. I know the flow differences aren't a lot, but I know from experience any amount of flow difference without a proper tune can cause problems.

 

If the flexplate/flywheel was already installed on the motor then yeah it's probably in the correct position.

As far as injector compatibility that's not a problem it's all the same flow rate and voltage, the reason you keep your existing injectors is because you have no idea what condition those donor motor injectors are in. Usually they chop out the engine, then it just sits for a year or more before being shipped to the US (doesn't ship until they fill the rest of the conex being shipped. Those injectors could be completely screwed up.

I've unloaded JDM engine conexes before. They strap a bunch of engines to a pallet, then forklift the pallets up into a conex and stack them 3-4 high. Those engines sat outside on the pallet for a while, sometimes a VERY long while judging it based on the level of rust and corrosion. The fuel in those injectors lacquers up and clogs them.

That's not even counting the time the JDM car sat at the chop yard before getting it's engine cut out lol that thing might not have even been running for 3-4 years.

I have literally never used donor motor injectors, it's something that you always keep your originals. Normally we just take all those old injectors and toss them in the dumpster lol.

What I'd recommend if time isn't an issue but you want to be more cost effective is to take the wet cylinder and swap it's injector to another cylinder. Then see if the other cylinder won't fire.

That way it doesn't cost you money throwing parts at the car, but my gut feeling is your buddy is going to be buying 6 new injectors.

You can also check spark though, take out the wet cylinder spark plug, put it back in the coil pack, then hold the ground strap 1/4" away from the intake plenum while someone else cranks the engine and visually check spark. Pull the fuel pump relay first so the engine doesn't start up.

 

I plan to check for spark as well, I have a couple spare injectors that I grabbed at the yard just to check them. He wanted to send out all 6 to get rebuilt and flow tested anyway, so that issue should be taken care of. This engine came from a local full service yard, but in the same case, who knows how long it was sitting.
Thanks for the clarification on the injectors, when I saw the numbers I figured they shouldn't make a big difference but you never know.

We swapped the original flywheel over from the original motor since the donor motor was from an automatic, but it should have been aligned. It's been a while, so I don't remember exactly. I'll keep that in mind though if we don't figure this out.

I'm hoping we'll get a chance this weekend to diagnose this more, since it'll be much cooler than last weekend (it was in the high 90s... ugh!). I'll keep you posted!

 

If the flywheel isn't clocked correctly it will run TERRIBLY, it can easily be mistaken as a misfire.

 

That's good to know, I've just been doing some reading on that. I'll have to confirm that he installed the flywheel correctly, because I don't think I was there for that. I hope so, because I doubt he wants to drop the transmission lol.

 

Fortunately on this car dropping the transmission is easy. Everything is accessible and you don't have to play contortion games to reach stuff. I've done it so many times I have it down to about 30 minutes to remove.

The hardest part is the catalytic converter bolts that face toward the front of the car, use 36" worth of extensions and do it from the engine bay, remove the intake tube on the left side for access.

 

True, it's not a horrible job. We dropped it before to change the clutch, before we realized that the old engine was knocking. Then swapped the engine a few weeks later... and a year later, here we are! We plan to tear into it more tomorrow, so I'll update this thread with our findings!

 

Not to be too controversial, but if the injectors were at fault, a rich condition would mean the injectors are bigger than the computer thinks, so it would be bringing too much fuel in. On cars where you have a programmer, this is easy to fix, just keep adjusting the injectors smaller in the software until it's flowing the way you want. I don't think your injectors are at fault here at all.
However, your upstream O2 sensor sitting at such a high number, Now thats an issue. I just looked at mine last night, and that number is what mine are when cold, so it's either bad or lazy or something wrong in some way with the sensor. Or possible the wiring to it.
I suspect a leak myself, but I will be very interested to hear what you find.

 

I agree that the injectors are unlikely to be an issue, but this is running very rich. That said, the fuel trims are very high, so I think it's running this rich because the ECU is commanding all the extra fuel. That would lead me to suspect a large vacuum leak. The Bosch injectors (which are installed) are rated higher than the JECS injectors, but it's not by a lot.
We went to the junkyard this past weekend and grabbed a good intake tube, so hopefully he'll be able to throw that in at some point this week and we'll see what happens. I feel like we're getting close to a solution here, the car is just very picky about all of the small issues since dropping this engine in.

 

I agree on a vacuum leak, it will cause a rich condition.
It's why , generally, I start at the top and work my way down when presented with this kind of situation when dealing with a mysterious leak. Replace the valve cover gasket, spark plug tube seals, the valve cover to valve cover hose (I bet it's cracked), PCV and hose, intake gasket, check all bolts for looseness, etc. Also those upstream sensors if not done should also be replaced. Tedious ubt not hard to do.

 

Yup, that's basically what I suggested for him to do. The PCV hose is cracked now, I cracked it when I was pulling out the cylinder 1 coil lol. That's on the list.

 

The other thing you could do to deal with fuel trims is put in an adjustable fuel pressure regulator and drop the pressure on it a little to make it spray less. On a stock setup, I believe that's about a 290cc injector at 43PSI, so if you do this, you can drop this a bit and get the injector to behave smaller.
There is a formula for this:
[Advertised Flow Rate] X [The Square Root of (Your Pressure ÷ Rated Pressure)]
But mainly just drop it 1-2 PSI at a time and watch the lean/rich and you should see it get better.

Now, I only suggest this because you said it's possibly due to a slightly different size injector.

It's just an idea. I've done this before on other cars and it's been great to be able to tune via the adjustable regulator.

 

The ECM can pull out like 25% fuel before it turns on the CEL so technically you can just let it handle the math unless you have around 25% bigger injectors. Not the prettiest way of doing it though