Ladies and Gents, thought I would share some notes on how I swapped the JDM F23A for the F23A4 (ULEV) in a 99 accord. Hope the info is useful.

My experience with the 98 thru 02 F23A4 (ULEV engine) has not been good. I have had 3 ULEV engines fail internally resulting in "chocolate milkshake" coolant, that is engine oil in the coolant (you can also have strawberry milkshake coolant). I have not had coolant in the oil however. In general my experience is this is not a head gasket failure, although on at least one engine the head gasket also failed. The oil in coolant failure for the F23A4 is believed due to the block cracking in the vicinity of an oil galley, and the oil pressure being higher than the coolant pressure forces oil into the coolant system. I suspect there is a region of the block that is cast too thin and/or porous and thermal stress cycling eventually causes the crack to develop, I have tried to find the crack and have been unsuccessful... The failure might be near a head bolt hole, thus a region of stress concentration. Whatever the reason they fail for me at around 150k miles.

So this time, being the glutton for punishment that I am, I opted for a F23A JDM engine to install in a 99 Accord LX 4DR F23A4 (ULEV). In reality I tinker on stuff. I got the engine from one of the northern Virginia JDM engine shops, the three that I know of are all pretty much the same in terms of inventory and price. I had them do a compression test, 180 psi on all the cylinders, I looked at the dip stick (clean), inside the oil cap (no coolant or crud) and cam cover (no sludge evident) and looked for oil in the heater hoses, thermostat outlet and head inlet (nothing slimy feeling, smelling like oil or bloated hoses). You should pull the EGR and see if there is heavy carbon build up, I didnt do that. Also pulled the pcv hose to see if its clogged. Another tip is to buy or borrow a 9mm or smaller snake camera and look inside the cylinders for excessive carbon, wall scoring and valve/piston impact. I think the reason there are so many engines available is the japanese fail engines due to hydrocarbon emissions being too high and leaks, i'll bet in a significant number of cases its due to the pcv being stuck and the cam cover leaking a little, i.e. wont pass the white glove inspection...

When I got the engine to my shop the first thing I did was remove the cam cover to make sure the head wasnt sludged, it was like new, not even a baked brown film... I next pulled the intake plenum, it had a thin layer of build up and the egr port had a small amount of carbon crust, but completely open. ND plugs looked very good. So I would say the engine looked like it had at least 50k miles but could be a lttle more. The cam cover gasket was seeping slowly at the dist and belt ends, only minor crud on the outside mainly behind the ps pump. I also drained about a quart of old oil from the sump, it was dirty but not black, and there was no water. So in the end it looked worth committing the time to use this engine.

There is all sorts of advice as to what JDM external parts can be used, here's what I found (YMMV):

1. Exhaust manifold: Since I was using the F23A4 ECU and AF sensor and retaining all the existing exhaust system I swapped the USDM F23A4 exhaust manifold for the JDM manifold. On a F23A1 swap you may be able to use the JDM exhaust manifold if you can find the correct 2 into 1 exhaust pipe, maybe a pipe from an aftermarket tube header will work.

2. VTEC: The F23A and F23A4 are both VTEC, however the JDM VTEC spool valve housing is missing the VTEC pressure switch the USDM engines have. I removed the plug and screwed in the switch from the F23A4. Pay attention to the harness connectors, the VTEC switch can be mixed up with the fan temp switch, both are round two pin connectors. The VTEC pressure switch connector is typically a light green color, the fan switch is typically gray. I also checked the resistance of the VTEC solenoids, both JDM and USDM are 15 ohms (both have identical single pin connectors) so I did not swap the solenoids.

3. AC compressor bracket: If you have AC then the JDM AC bracket must be swapped for the USDM bracket, the brackets are not the same. My engine didn't come with a compressor but it looks like the JDM compressor may be smaller. Bracket bolts are the same.

4. Crank timing sensors: The connector and measured sensor resistances, 2.1k ohms, are identical between the JDM and USDM so I did not swap the crank sensors.

5. Harmonic damper and PS: The JDM engine I purchased had a JDM power steering pump, however the PS pulley on the damper is significantly larger in diameter than the USDM damper and the JDM pump has a smaller pulley than a USDM pump. So I swapped the JDM damper for the USDM damper. I also swapped the JDM PS pump for the USDM pump. You could possibly use the JDM PS pump and damper but I swapped it for 2 reasons, 1) i don't know if the system pressure is the same and 2) I want to retain the USDM PS belt size. The JDM PS pump bracket can be retained. Also the JDM pump has its inlet pointed away from the feed hose making its use tricky.

6. Balancer shaft seal retainer: I pulled the timing belt covers to inspect the belts, tensioners, water pump and to see if the engine had a seal retainer on the left balance shaft. The belts, water pump and tensioner looked brand new so I didn't replace anything, however the seal retainer was missing. I installed the retainer from the F23A4, it fit perfect.

7. Alternator: The JDM engine came with an alternator and I retained it. Note however the multi pin socket is located on the back of the alternator. The USDM alternator locates the socket on the side. Fortunately the harness was long enough for the connector to reach the JDM socket and they are compatible. When I started the engine for the first time I checked that it was putting out the correct charging voltage, it did and no codes were set.

8. Head sensors: The JDM had the correct ECU temperature sensor installed, but it had a plug in the place of the small sensor used for the instrument cluster. I swapped the small temp sensor from the F23A4 into the F23A. The fan switch sensors are identical, fans switched on at 203F.

9. Distributor: The JDM and USDM distributors have identical 4 pin connectors, but I consistently read where folks use the USDM distributor. So I swapped the USDM distributor for the initial startup. After I got it running correctly I swapped the JDM back, the engine ran the same, no codes, no idle issues, so I conclude the distributors are practically identical.

10. Intake manifold: The JDM intake plenum, lower manifold and injectors are different. However the dimensions of the ports, runner length, plenum size and throttle body diameter are identical to the F23A4, so contrary to some reporting that the USDM manifold is smaller and more restrictive that appears not to be the case.

The JDM injectors and fuel rail is very different. The JDM injectors while having the same connector are much shorter in length and have a smaller diameter body and pintle. Thus the injector holes in the JDM manifold are different from the USDM manifold. The JDM fuel rail locates the fuel feed banjo bolt at the far right end of the rail, this makes the USDM fuel feed hose too short.

Also, the JDM plenum lacks the needed 4 vacuum ports, it has 3 ports, and the JDM throttle body had a broken TPS socket and lacked the cruise control cable pulley.

All these differences and not knowing if the injector signals are compatible is the reason I swapped out the JDM intake.

However there are perfectly compatible parts that can be salvaged off the JDM intake. Such as the throttle body (if you don't need cruise control), MAP sensor, intake air temp sensor, IACV, pressure damper and purge solenoid. The fuel pressure regulator may be usable but it has a long connector that may cause issues with the existing return line length.

When hooking up the intake pay attention to the TPS and MAP sensor connectors, they can be reversed. The blue connector goes to the TPS. Double check that all the vacuum lines are connected correctly, in particular check the vacuum line that runs under the intake to the iacv.

11. Water pump outlet coolant tube: I didn't catch the difference between the JDM and USDM tubes immediately, but the JDM tube locates IACV heater line outlet closer the water pump end of the tube. This means the USDM feed hose to the IACV is too short, so I used the JDM hose which is fortunately in good condition. So you may want to swap the tube while the engine is on the stand so you can use a USDM hose.

12. I pulled the engine and trans as a unit out the top, to do so remove the intake, radiator/fans, starter (optional), battery shelf, ac compressor, exhaust pipe from manifold, shifter cable, wiring harness, distributor. Then the engine mounts. I use an engine crane and a load leveler I bought at harbor freight (worth it). Its straight forward for one person using the leveler. You do not need to remove the hood or ac lines, the ac compressor can remain connected just locate it to an area at the base of the ac condenser. Its tight and you can get more side to side room by removing the harmonic damper, I typically don't. I also remove the two long transmission mount studs on the passenger side mount, this helps in getting the mount in and out. I permanently replace the studs with bolts.

13.The f23A4 intake was stripped down and cleaned. The IACV was cleaned thoroughly as was the throttle body passages. Be careful not to get anything inside the TPS. The TPS is a very sensitive rotary potentiometer and can be ruined if solvent gets inside, same for the MAP sensor and stepper motor attached to the IACV. I use a high quality silicon lubricant on all the o-ring seals.

14. Get a radiator funnel kit to assist with getting the air out of the coolant system, worth the price.

15. The engine started right up, runs very well and is quiet. No codes, idles steady at 700 rpm and 21.7 in-Hg vacuum, no leaks, no smoke, VTEC engages, temp, o2 data and fuel trim all look good.

16. Parts I replaced:

1. coolant tube o-ring (31.2X4.1) (Nok) 91314-PH7-003
2. Gasket, Thermostat Case 19313-PT0-000
3. Gasket A, In Manifold (Nippon Leakless) 17105-PAA-L01
4. Gasket, Ex Manifold (Nippon Leakless) 18115-PAA-L21
5. cam seal (bought but not replaced)
Oil Seal, (28X42X8), (Arai) 91213-PT0-003
6. Distributor seal/o-ring, 30110-PC6-005
7. Heater hoses:
Hose A, Water Inlet, 79721-S84-A00
Hose B, Water Inlet, 79722-S84-A00
Hose, Water Outlet, 79725-S84-A00
8. Hose, Rotary Air Control Valve-In, 19509-PAA-A00
9. Hose, Rotary Air Control Valve-Outlet, 19510-PAA-A00
10. Hose B, Breather Heater, 19515-PAA-A00
11. Hose A, Breather Heater, 19514-PAA-A00
12. Tube, PCV, 11856-PAA-A00
14. Rear seal Oil Seal (80X100X10) (Nok) 91214-PLE-003
15. Honda-Rodent-Proof-Electrical-Tape, 4019-2317
16. Sensor Assembly, Knock, 30530-P5M-013, ks64
17. PCV Valve Assembly, PCV 17130-PK1-003
18. Thermostat Assembly (Nippon Thermostat) 19301-PAA-306
19. Gasket Set, Head Cover 12030-P0A-000, Use hondabond in the gasket corners
20. timing belts, water pump (bought but not replaced):
Belt, Timing, 14400-PAA-A02, Bando TB244
Belt, Balancer Timing, 13405-PAA-A03, Bando TB186
Water Pump, 19200-P0A-003, Aisin WPH-001
21. Timing belt tensioners (bought but not replaced):
Adjuster, Balancer Belt, 13404-PT0-004, koyo PU277027HRR1ZS1
Adjuster, Timing Belt, 14510-PT0-004, koyo PU326231GRR1DV
Tensioner spring, 14515-P0A-000, came with the koyo tensioner
Tensioner spring, 13407-P0A-000, came with the koyo tensioner
22. push clip ties 20pcs
23. downstream o2 sensor, denso, 234-4621
24. A/C COMPRESSOR BELT, 38920-PAA-A01
P/S PUMP BELT, 56992-P0A-J01
Bando set, 4PK1065, 6PK1105
25. Filter Assembly, Spool Valve (VTEC), 15825-P0A-015
26. Gasket Thermostat Case 91312-P0A-000
27. 17138-P0A-000 Tube, Breather
28. 18212-SM4-003 Gasket, Ex Pipe (Ishino)
29. 19501-PAA-A00 Hose, Water (Upper)
30. 19502-PAA-A00 Hose, Water (Lower)
31. 36461-PAA-A01 Gasket, Rotary Air Control Valve
32. 16176-PAA-A02 Gasket, Throttle Body (Nippon Leakless)
33. 17115-PAA-A01 Gasket, In Manifold, plenum (Gemstone)
34. 18715-PB2-000 Gasket, Egr Valve (Ishino Gasket)
35. 91312-P0A-000 Gasket, Thermostat Case
36. o2 Sensor, Air Fuel Ratio, 36531-PAA-307, denso 234-9025
37. cat converter, magnaflow 22642
38. honda antifreeze, OL999-9011
39. oil, mobil-1, trans fluid, maxlife
40. assortment of metric o-rings

 

Excellent detail. I'm considering this right now with my '02 Accord. It has had bad rings in #3 cyl and I've been nursing it a long for many years. Last August it burned a valve (I think) and needs work. But I'm in CA, so I need to pass smog. My one issue, aside from the work, is will going to an F23A1 block in place of my F23A4 block cause any issues for me when I go to smog it? In theory the blocks are all the same, but the casting numbers are large and in plain sight. I like the JDM option, but I'd hate to spend $500+ and put in a long weekend only to find it doesn't pass the visual inspection and can't be made to.

 

Thank you for this thread. I found it useful planning for f23 JDM swap in my 2001 accord.

 

Yeop.
Lotta the JDM stuff is similar yet different.
Easiest thing is to merely strip down the long block and bolt on the original engines components. Tried to not do that on my own F22B1 to replacement F22B engine, and the most mundane components were very similar but would not interchange with the USDM parts. Also if a component fails you are still just using USDM parts and can readily get those components/rebuild kits. Add some funky JDM bit because, reasons, and you will be hating yourself when you can't find the correct rebuild kit of component for your otherwise USDM vehicle.

Doubt any of the smog shops would even know where to look or care. They are just making sure everything looks kosher. And nothing is gleaming like a massive turbo or shiney parts.
If it looks factory stock they won't blink. I would suggest keeping your original green painted 'ULEV' cam cover to prevent any additional questions.
FWIW, JDM engine usually are just F23A, or H22A, there are no numerals after the fact. And here in Calif CARB considers a JDM engine the same as the USDM version.

 

Adding in my own experience doing the same swap and notes that would add to the above. As Mad Mike said, I would steer clear of attempting to make any JDM sensors or external parts work, it will confuse the next person trying to replace the item (such as an alternator).

Further details here, including pictures of items such as the transmission solenoids that should be swapped over.

https://honda-tech.com/forums/honda-...thers-3345715/

 

The bearings on my old Alternator feel coarse so I will be using the JDM atlernator.

 

This might sound silly, but if you do use a JDM component, put a note on it (tape with writing I suppose) stating that this is not a US version, and that the US version will be different. Helps yourself or the guy in the future replacing that part later.

 

I have owned this car for over 9 years. ‘Till rust do us part.

 

Understood. Several cars in the family we have had for over 20 years now. Disintegration or Death.

 

I just finished the swap and here is my contribution. (some info redundant to OP)

I swapped an F23A in lieu of my F23A1 in a 2001 accord.

Exhaust - used my USDM exhaust manifold

Intake manifold- Used the JDM manifold , JDM injectors because USDM injectors dont fit in the JDM intake manifold, used the USDM fuel rail because the fuel inlet is in a different location, used USDM throttle body because the JDM one doenst have cruise control. The JDM intake manifold is missing one tiny vaccum port so I ran a "Y" connector to run two vaccum lines on the same port.

I used the JDM rear coolant pipe and T-stat housing. (you need a longer little coolant line from the IACV to the coolant outlet near the water pump, USDM hose is too short - ran a generic coolant line - Otherwise is same as USDM

Added a missing sensor from USDM vtec selenoid to JDM vtec selenoid.

Used the JDM Crank pulley - the Alternator/AC pulley is the same size as USDM but the power steering pump pulley is bigger on the jdm crank pulley.

JDM crank pulley + JDM alternator + USDM AC compressor and AC compressor bracket - Needed longer belt because althou the JDM alternator has the same size pulley as USDM, it is shaped differently and the pulley is farther away than if you use the USDM atlernator- need belt 6PK1120 (6 row, 1120mm) part number - 4060440 Serpentine Belt- Continental Elite

JDM crank pulley + USDM PS pump - need longer belt because of larger crank pulley - 4PK1090 (4 row 1090mm) part number 4040430 Continental Elite

Car runs great, no noticeable difference in performance

 

Very interesting on the belt sizes. Probably good to add that here as well for the varations

In may case :

JDM Crank Pulley +US alternator + US compressor and AC bracket = 6K435 belt
JDM Crank Plley + USDM PS Pump = 4PK1085 (very close to what you had, just 5mm shorter, I just went a hair smaller )

 

For the PS I tried a 4PK1085 and it works but you have to somewhat force it onto the pulleys.

 

Yeah, like I said it was interesting because I tried the 4pk1090 and I thought it was too loose

It's such a small difference, but I thought it is a good touchpoint in case there are variations as others install theirs.

 

Hello, I'm currently in the process of swapping a F23A4 blown motor into a F23A for my accord manual as well. Is it possible to swap the JDM external parts of the front of the engine and just use USDM part with their respective belts? Like for example, switching the JDM crank pulley and putting in the USDM crank pulley. Consequently, changing the JDM alternator, JDM AC Compressor and brackets, and JDM power steering pump and brackets to USDM?

 

Do you mean replacing an F23A4 with an F23A?

As mentioned before, strip down the F23A engine to its long block, replace rear main seal even if its not leaking.
Install all components from the original engine onto the replacement.
Distributors, intake and other parts are just different enough not to work with your cars harness.