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H22 Swap Thread - All known swaps to date and parts list:

General '88 - '91 Prelude Discussion
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1funryd United States of America
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Joined: 18 Aug 2017, 00:41

H22 Swap Thread - All known swaps to date and parts list:


Post by 1funryd » 01 Nov 2018, 06:06

Update: 6-26-16 - 88-91 Prelude H22 swap video - 1FunRyd's swap.

Since we have grown more in this arena, I decided to make a thread that lists all know H22 swaps. If you are doing such a swap, please let me know and point me to it and I will add it to the list. I am going to put this thread in the Performance Upgrade Inventory thread.

H22 Parts list for those wanting to swap to the might H/F motors:

Click here --> H22 Swap Checklist - Parts to get... 1FunRyd

PowerSteering Civic fitting to get the best clearance for the powersteering hoses at the pump to the resevoir.
Part numbers: 56123-P30-000 (JOINT, INLET) and one 91345-PY3-000 (O-RING (13.0X1.9)
osvaldo516;2794307 wrote:I used stock one just turned around 180degrees.

you will need one 56123-P30-000 (JOINT, INLET) and one 91345-PY3-000 (O-RING (13.0X1.9). this will make the p/s pump connector point sideways towards the p/s reservoir instead of pointing down and use the stock hoses and the one that came with the tl reservoirs that connects to p/s pump

For Keeping A/C working in your H/F series swap

H22 Swapped 3rd Gen Preludes - Build threads

1. 1FunRyd's - Auto to 5 speed swap, B20A - H23 Non-VTEC swap (Image 1 2 3 ... Last Page)

2. teams ranfla (H22 start up video on page 4) (Image 1 2 3 ... Last Page)

3. osvaldo516's ghetto h22 swap update (Image 1 2)

4. 600HP H22 Boosted 3GP - OMG!!!!! (Image 1 2 3 ... Last Page)

5. AZ Race H22 3g Mounts Review - rudeludenotmeanthough

Image 88S to JDM H22A build thread. (Image 1 2 3 ... Last Page)

7. H22A swap progress (Image 1 2)

8. Tengoku's H22a Swap and Mods Thread **Pics Inside** (Image 1 2)

9. H22 swap...startup tomorrow - pics inside..... (Image 1 2 3 ... Last Page)

10. Poll: H23vtec or boosted H23? Need some opinions. (Image 1 2 3)

11. My 3rd Gen H22A Swap Project - PROGRESS - 56k NO WAY (Image 1 2 3 ... Last Page)

12. jdm3genprelude's h22a dyno/tuned

13. 88 honda prelude progress thread.

14. 3rd Gen_ Ludercrs' Blue H22A 1991 Prelude SPECIAL EDITION

15. Another engine swap....This time bigger is better!! (Image 1 2 3 ... Last Page)

16. Netzyo's new addition to the fam. 91 si (Image 1 2 3 ... Last Page)

17. 3rd Gen_ Black Majik Steering-H22 Swap....long story!

18. my lude (race h22 project) (Image 1 2 3 ... Last Page)

19. finaly started h22 swap (Image 1 2 3 ... Last Page)
Image a1cnas

20. :Lucky Never Dies: Raspinudo's Progress Thread (Image 1 2 3 ... Last Page)

21. 91 4WS H22 Swap (Image 1 2 3 ... Last Page)
Tim Hartman

22. 1991 Honda Prelude H22A Restoration! (Image 1 2 3 ... Last Page)

23. blahblah311 Starts Fresh. New build thread. (Image 1 2 3 ... Last Page)

24. 3rd Gen_ Yet Another Friken H Swap Thread Part-9 © MMXII (Image 1 2 3 ... Last Page)

25. Steve's H22a swap

26. Rev_rage Vs Prelude Round 2 title fight

Carbed Prelude to H22 swap:

1. 88-91 Prelude Carburated to H22 swap

B Series Swaps to date:

For the B16/18/20B series swap kit here is the thread I created for the group buy - 1FunRyd 88-91 Prelude - B16/18/20b Series mount Swap kit

1. 1FunRyd Performance - 88-91 Prelude B20b/z swap

Image B18C-R progress thread. (Image 1 2 3 ... Last Page)

Here is the B20a5 ECU pinout for those who do their own wiring:

*Here is some important information for those who purchase an H22a4 for their swap.*

Originally Posted by nusdogg Image
You'll need to get a H22A1 oil pump housing to replace your current one on the H22a4 or wired the CKP sensor on the oil pump housing on the A4 to the distributor, so it'll fire up.

Transmission information: Prelude/H-series Transmission Codes and Ratios master-list

Update: 12-16-2009

Here is a thread from Honda-Tech that will be crucial to those who want to swap a factory H23VTEC motor into our ludes:

1. JDM H23A Vtec Blue Top Mystery Motor, True Facts, Questions?

Questions regarding the H22 swap into the 3rd gens and all related questions thread:
  1. ask your H22 swap questions here...thread (Image 1 2)
  2. obd1 pinout questions....h22a swap (Image 1 2)

Converting AC wiring and lines to work for the H22/23 swap:
  1. H22/23 swap with AC...completed
What are the differences between the H22/23, F20b motors:
All the motors listed below will drop into our 88-91 Chassis using the 1FunRyd Billet H22 mounts and the ESP H22 mounts as well.

1. H22a1 OBD1 92-96 Prelude - USDM motor is the easiest motor to swap for using the P13 stock H22 ECU or tuning. This motor is 195-200hp - 161tq

2. H22a OBD1 92-96 Prelude/Accord - This is the JDM version motor and can be either the Prelude or Accord motor, and is usually OBD1, but you must verify with your engine importer if it is or not. This motor is 195-200hp - 161tq


3. H22a4 OBD2 97-2001 Prelude - This is the USDM 5th gen motor and can still be swapped, but will take some modification to convert to OBD1 for tunine or to use the P13 ECU. In order to use this motor, and you will need to change the distributor as well. This motor is 220hp - 161tq

*Here is some important information for those who purchase an H22a4 for their swap.*
nusdogg;2720625 wrote:...
You'll need to get a H22A1 oil pump housing to replace your current one on the H22a4 or wired the CKP sensor on the oil pump housing on the A4 to the distributor, so it'll fire up.


This is the Type S Redtop H22a4 motor:
This motor is rated at: 220hp 163tq


4. H23A DOHC Non VTEC Engine 92-96 - This the JDM version Non-Vtec motor and is OBD1. And is relatively easy to swap with just the engine harness and an OBD1 conversion for the 88-89 Preludes.
This motor is rated at 160hp - 163tq


5. H23a1 DOHC Non VTEC Engine 92-96 - This is the USDM Non VTEC OBD1 motor and is relatively easy to swap with just the engine harness and an OBD1 conversion for the 88-89 Preludes. This motor is rated at 160hp - 163tq

6. H23a3 DOHC Non VTEC Engine 92-96 - This is the USDM OBD2 version of the H23a1. This motor is rated at 160hp - 163tq

7. H23A DOHC VTEC Engine BlueTop only 97+ - OBD2 JDM motor - This is the Frankenstien motor built from Honda in OEM form. It is combination of an H22 head, on an H23 block. It uses the longer stroke for the extra torque, and then uses the higher reving VTEC head of the H22. This does not mean that you can rev it out to the same redline of an H22, but you will get your power delivery much quicker with this motor, and if you build the bottom end, you can rev it past its 7000rpm limit.
This motor is rated at 197hp-163tq


8. F20B DOHC VTEC - Honda Accord 97-01 - This is the Euro Accord motor and has a higher rev line, but it is a 2.0l discplacement. The engine cast is still the same dimensions as an H22. This motor looks exactly like the H23avtec Blue top motor so make sure to take a close look at the engine stamp. This motor is rated at 200hp - 147tq


9. F22B DOHC Non VTEC Engine - Accord 90-97 - This is the USDM Accord and Prelude non-vtec motor. It is OBD1. This motor is rated at 150hp - 145tq


10. F22B SOHC VTEC Engine - Honda Accord 94-97 - This is the Accord Single Over Head Cam VTEC motor. It is OBD2 and will need to be converted to OBD1 to run. Redline was 6200 at a Rev limit of 6500rpm.
This motor was rated at 145hp - 147tq


11. F23A SOHC VTEC Engine - Honda Accord 98-02 - This is the Accord Single Over Head Cam VTEC motor. It is OBD2 and will need to be converted to OBD1 to run. This motor was rated at 150hp - 152tq



H22/23 F22/23 Engine specifications:


Block Type
H22A4 Block = Open Deck
H22A block = Closed Deck
H23A-BlueTop block = Open Deck
H23A-JDM(non-vtec) = Closed Deck
H23A1 block = Closed Deck
F22 block = Open Deck
F23 block = Open Deck
F20B block = Open Deck

Deck Height
H22A4 Block = 8.643
H22A block = 8.643
H23A block = 8.643
H23A1 block = 8.643
F22 block = 8.643
F23 block = 8.643
F20B block = 8.643

H22A4 Block = 87mm/3.425
H22A block = 87mm/3.425
H23A block = 87mm/3.425
H23A1 block = 87mm/3.425
F22 block = 85mm/3.346
F23 block = 86mm/3.385
F20B = 85mm/3.346

Due to various available piston diameters (A/B) actual bore diameter may vary


H22A4 = 5.633
H22A = 5.633
H23A = 5.572
H23A1 = 5.572
F22 = 5.572
F23 = 5.551
F20B = 5.709

H22A4 = .935
H22A = .935
H23A = .935
H23A1 = .935
F22 = .935
F23 = .780
F20B = .935

BE Bore
H22A4 = 2.008
H22A = 2.008
H23A = 2.008
H23A1 = 2.008
F22 = 2.008
F23 = 1.890
F20B = 1.890

Pin Bore
H22A4 =
H22A = .8649-.8654
H23A =
H23A1 = .8649-.8654
F22 = .8649-.8654
F23 = .8649-.8654
F20B =


H22A4 = 87mm/3.425
H22A = 87mm/3.425
H23A = 87mm/3.425
H23A1 = 87mm/3.425
F22 = 85mm/3.346
F23 = 86mm/3.385
F20B = 85mm/3.346

actual diameter may vary depending on code of piston (ie, A B)

Compression Height
H22A4 = 1.221
H22A = 1.221
H23A = 1.203
H23A1 = 1.203
F22A1 = 1.203
F22A4 = 1.203
F23A1 = 1.181
F20B = 1.221

Dome Volume
H22A4 =
H22A =
H23A =
H23A1 =
F22A1 =
F22A4 =
F23A1 =
F23A4 =
F23A5 = -18cc
F20B =

Wrist Pin Diameter
H22A4 = .866
H22A = .866
H23A = .866
H23A1 = .866
F22 = .866
F23 = .866
F20B = .866


H22A4 = 90.7mm/3.570
H22A = 90.7mm/3.570
H23A = 95mm/3.740
H23A1 = 95mm/3.740
F22 = 95mm/3.740
F23 = 97mm/3.818
F20B = 88mm/3.464

Main Journal Diameter
H22A4 = 55mm
H22A4 = 50mm (1997 Only)
H22A = 50mm
H23A = 55mm
H23A1 = 50mm
F22 = 50mm
F23 = 55mm
F20B = 55mm

Rod Journal Diameter
H22A4 = 1.888
H22A = 1.888
H23A = 1.888
H23A1 = 1.888
F22 = 1.888
F23 = 1.771
F20B = 1.771

Cylinder Heads

Combustion Chamber Volume
H22A4 = 53.8cc
H22A = 53.8cc
H23A = 53.8cc
H23A1 = 50cc
F22A1 = 50cc
F22A4 = 50cc
F23A1 = 50cc
F23A4 = 50cc
F23A5 = 50cc
F20B =

Intake Valve Diameter
H22A4 = 35mm
H22A = 35mm
H23A = 35mm
H23A1 = 34mm
F22 = 34mm
F23 = 34mm
F20B = 34mm

Exhaust Valve Diameter
H22A4 = 30mm
H22A = 30mm
H23A = 30mm
H23A1 = 29mm
F22 = 29mm
F23 = 29mm
F20B = 29mm

Head Gaskets

H22A4 = 88mm
H22A = 88mm
H23A = 88mm
H23A1 = 88mm
F22 = 86mm
F23 = 87mm
F20B = 86mm

H22A4 = .026
H22A = .026
H23A = .026
H23A1 = .026
F22 = .026
F23 = .026
F20B = .026

Gasket thickness measured after crush


Main Bearing Thickness
2.013 - 2.010mm / 0.0793 - 0.0791
2.010 - 2.007mm / 0.0791 - 0.0790
2.007 - 2.004mm / 0.0790 - 0.0789
2.004 - 2.001mm / 0.0789 - 0.0788
2.001 - 1.998mm / 0.0788 - 0.0787
1.998 - 1.995mm / 0.0787 - 0.0785
1.995 - 1.992mm / 0.0785 - 0.0783

Rod Bearing Thickness
1.510 - 1.507mm / 0.0594 - 0.0593
1.507 - 1.504mm / 0.0593 - 0.0592
1.504 - 1.501mm / 0.0592 - 0.0591
1.501 - 1.498mm / 0.0591 - 0.0590
1.498 - 1.495mm / 0.0590 - 0.0589
1.495 - 1.492mm / 0.0589 - 0.0587
1.492 - 1.489mm / 0.0587 - 0.0586

Main Bearing Width
H22A4 = .784
H22A = .784
H23A = .784
H23A1 = .784
F22A1 = .784
F22A4= .784
F23A1 = .784
F23A4 = .784
F23A5 = .784
F20B = .784

Rod Bearing Width
H22A4 = .762
H22A = .762
H23A = .762
H23A1 = .762
F22A1 = .762
F22A4 = .762
F23A1 = .609
F23A4 = .609
F23A5 = .609
F20B = .762

Found on Honda Tech "The official H/F piston/rod/crank/block specs and CR thread" thread.

Another thread on H/F series blocks on preludepower: H/F series motor information for h22 swap guys


Do It YourSelf H22 Valve adjustment <---- Click here

OBD1 - ECU Codes:

Once you get the CEL light to blink, here's the how the light is read:

1 long blink w/short pause = an incriment of 10
short blinks = incriments of 1
long pause = a break between codes

Another example:
fast blink = 1
Long blinks = 10
so if it does this !.........!........!.!.!.! that would be code 24

Example: say your CEL light is showing 1 long blink, short pause, 1 long blink quickly followed by 2 fast blinks, this is code 22 being flashed. Another example could be 10 fast blinks, semi-long pause, followed by 1 short blink - this would be two codes being flashed, code 10 & code 1.

It may take a few minutes to figure out what CEL codes are being thrown by your ecu.

As written out by Haynes. There are many many more... just not in Haynes.

OBD1 Trouble Codes

Code 0 Faulty PCM
Code 1 Oxygen Content
Code 3-5 Manifold Absolute Pressure (sensor)
Code 4 Crankshaft position sensor (CKP)
Code 6 Coolant Temperature
Code 7 Throttle Angle (TPS)
Code 8 TDC position
Code 9 No. 1 cylinder position (CYP)
Code 10 Intake Air Temperature (IAT)
Code 12 Exhaust Gas Recirculation System
Code 13 Barometric Pressure
Code 14 Idle Air Control (IAC) valve
Code 15 Ignition output signal
Code 16 Fuel Injector
Code 17 Vehicle speed sensor (VSS)
Code 19 Lock-up Control Solenoid
Code 20 Electronic load detector (ELD)
Code 21 Variable Valve Timing and Valve Lift Solenoid - VTEC solenoid check
Code 22 Variable Valve Timing and control pressure switch
Code 23 Knock Sensor
Code 30 A/T FI signal A, (Automatictransmission vehicles)
Code 41 and 48 Oxygen sensor heater
Code 43 Fuel Supply System

You can do the pinout yourself and make your own harness for free here is the the pinout: -----------------------------------------------------------------------------------------
OBD1->OBD0 - Function

OBD1->OBD0 - Function
A01 ->A01 - #1 injector
A02 ->A07 - #4 injector
A03 ->A03 - #2 injector
A04 ->N/C - VTEC solenoid Valve
A05 ->A05 - #3 injector
A06 ->N/C - O2 Sensor Heater Control
A07 ->A12&A14 - Fuel Pump Relay (FLR1)
A08 ->N/C - Fuel Pump Relay (FLR2)
A09 ->A11 - EACV
A10 ->N/C - EGR solenoid valve
A11 ->N/C -
A12 ->N/C -
A13 ->B06 - Check Engine Light (MIL)
A14 ->N/C -
A15 ->B01 - A/C Clutch Relay
A16 ->N/C -
A17 ->N/C -
A18 ->N/C -
A19 ->N/C -
A20 ->B02 - Purge Control Solenoid Valve
A21 ->B15&B17 - Igniter Power Source (IGP1)
A22 ->N/C - Igniter Power Source (IGP2)
A23 ->A02 - Power Ground (PG1)
A24 ->A04 - Power Ground (PG2)
A25 ->A13 - Main Relay IGP1 (IG Power)
A26 ->A18 - Logic Ground (LG1)
A27 ->N/C -
B01 ->A15 - Power Source (IGP2)
B02 ->A16 - Logic Ground (LG2)
B03 ->N/C -
B04 ->N/C - Service Check Connector
B05 ->B08 - A/C Switch (ACS)
B06 ->N/C -
B07 ->N/C -
B08 ->N/C - P/S Pressure Switch
B09 ->B13 - Starter Switch Signal (STS)
B10 ->B16 - Speed Sensor
B11 ->C01 - CYL Sensor
B12 ->C02 - CYL Sensor
B13 ->C03 - TDC Sensor
B14 ->C04 - TDC Sensor
B15 ->B10 - Crank Angle Sensor
B16 ->B12 - Crank Sensor
D01 ->A17 - Back Up Fuse
D02 ->N/C - Brake Switch
D03 ->N/C - Knock Sensor
D04 ->N/C- Service Check & Ignition Timing Connector (SCS)
D05 ->N/C -
D06 ->N/C - VTEC Pressure Switch
D07 ->N/C - Data Link Connector
D08 ->N/C -
D09 ->B14 - Alternator
D10 ->B19 -
D11 ->C07 - Throttle Position Sensor (TPS)
D12 ->N/C -
D13 ->C06 - TW Sensor
D14 ->C16 - O2 Sensor
D15 ->C05 - Intake Air Temperature Sensor
D16 ->N/C -
D17 ->C11 - MAP Sensor
D18 ->N/C -
D19 ->C15 - Sensor Voltage (VCC1)
D20 ->C13 - Sensor Voltage (VCC2)
D21 ->C14 - Sensor Ground (SG1)
D22 ->C12 - Sensor Ground (SG2)

you have to short pin D04 to GND in order to check your CEL codes. btw, this harness has produced no codes in my car, other than the one i was getting before i even installed it.. damn TPS..



Here is a graph of the necessary re-pin locations when you eighther do your own wiring harness or purchase the H22 conversion harness. Remeber they no longer accept the old H22 harnesses, they now produce brand new and warranted MIL Spec engine Race harnesses.

This graph below is for the already OBD1 ECU plugs in the B21a1 powered 90-91 Preludes only.


The 88-89 Ludes will need to buy the jumper OBD0 - OBD1 harness that has the vtec sub harness already wired into the jumber harness for the conversion. Below is what their OBD0 - OBD1 jumper harness looks like:


Here are the Pinouts for the 88 - 89 Preludes Only.


How to calibrate a TPS Sensor:

Original thread:
loosen the 2 screws that hold the tps sensor in place. Now u might have to notch them or cut them to be able to loosen them. next, backprobe the tps sensor ( the middle wire) which is the signal wire. Next turn the car to the on position but don't start it. Now check the voltage coming through the wire, it should be .45V at idle. If not, turn the tps sensor clockise or counterclockwise until the voltage reaches .45V. Once u reach the specific voltage tighten up the screws, and then check the voltage to make sure it's still at .45V. And ur done!

H23 Vtec conversion facts:

If you want to convert to an H23vtec which is a combonation of:

1. H22 OEM head - cams, cam gears, valves vtec solenoid, intake manifold and throttle body, thermostat housing with sensors(no modifications)
2. H23 bottom end(OEM) - complete rotating mass, pistons, rings, rods, crankshaft

In order to make this combonation work the following will need to be made, but nothing needs to be modified.

1. H22 timing sprocket(behind the crank pulley and timing belt plastic cover)
2. H22 water pump
3. H22 waterpipe(behind the block)
4. H22 Head Gasket
5. Remove the oil plug that sits at the backside of the block between the block deck and Head(I mean literally between the head and block).
6. H22 stock or ARP head bolts
7. H22 timing belt
8. Keep the stock H23 manual tensioner(trust me you will want to keep it)
9. H22 P13 or any OBD1 ECU that can be chipped and tuned that will support vtec.
10. Recommend getting the engine harness from

If you just want to get vtec, then no need to change the pistons and rings out, just put it all together and make sure everything is torqued properly and check to see of the rotating assembly rotates with no hesitation.
Then re-assemble, and put all lubricants in and start her up.
*Note: Please be advised that while you will get vtec, your compression will be lower than an H22 stock compression. This is due to bigger combustion chamber in the head of the H22.

If you want the power and compression of the H23a Vtec Blue Top motor that is a European and JDM stock motor, you will need to do the following:

1. Replace the OEM H23a1 pistons with H22 OEM piston and rings. When I say OEM, I mean OEM non modified H22 pistons and rings to match. They will bolt up to the OEM H23a1 rods.
  • Stock H22/23 bore size: 87mm
2. This will put the piston outside of the block @ TDC.

Here is a post from Sean(Rosko):
Rosko;44712339 wrote:...
As far as the H22 vs H23 pistons go, I never said that they had the same compression height. In fact I've made several threads and even detail it out on my website that the H22 piston is taller by half a millimeter or roughly .02" Yes of course when you use an H22 piston with an H23 crank and rods the piston will stick out of the block .02", thats perfectly normal for this setup and is shown in the pictures you, Blake, and I have posted. In stock (stock pistons) form this is perfectly fine. With most aftermarket pistons this is perfectly fine. It only becomes a problem if you go too much more than that out of the block or go with larger than stock pistons. Then you will need to modify the chambers and or run a thicker head gasket. Since your pistons are basically still stock size I wouldnt expect that you would have problems, but obviously you saw the issue and Mahle is one of the pistons that I have not ever ran in a setup so I cannot comment on those.

Roskos website with the different variations of H23 vtec builds:

H23 vtec builds -

The H23 Vtec Blue top is documented at:
There are more, but these were the ones with build threads, so if you want to join the list, then pm me and I will add your thread to the list.

Making VTEC work on the 88-89 Manual VSS sensors:

Source Thread: ... 213&page=5 - Post# 140
a1cnas;2484299 wrote:0bd0>B16 Speed Sensor White-Blue
this is on your factory 3rd gen loom on the 2.0 SI

OBD1->OBD0 - Function
B10 ->B16 - Speed Sensor
connect b16 to b10 via your 0bd1 conversion harness, to get the signal from your clusters internal vss to ecu. it basically reads off of your cruise control, so you must have a fuse in the location, you dont need the dashpot in the engine bay as mine is currently removed, but i will relocat later so i can still have it. this means your cable driven vss needs to be install in the newer tranny, it will not have a place to actually bolt down without some kind of self made bracket, mine is just sitting in there, been driving for over a week and it has not moved or decided to pop out, but i will later make something to hold her in place. On side note, if your speedo does not work, fix it or the ecu will think your still standing still and hit the nuetral rev limiter. as a precaution, make sure the screen on your vtec sol braket is clean and free of debree. if it is filthy you will get vtec off and on and throw a code 22, presure switch,
its the braket the the vtec sol and the presure switch r connected to. their is 3, 10mm bolts holding it to the head.

i hope this solves alot of head aches for you luders out there:mrgreen:

TroubleShooting VTEC Engagement:

Source Thread:

I think we should get some info together and post up some common problems, and maybe even have people post in here that have had problems in the past and how they fixed them, it just seems there are alot of people doing swap or that are just having problems getting it to work correctly

i will start gathering some information but i got some work to do, in the mean time if anyone has info to add please post

Problems and causes i have run into before:

Problems usualy brake down into 2 categories and sometimes include both: mechanical and electrical. the first thing when wiring in a swap or diagnosing a problem is to check and recheck and check 50 trrilion times your wiring, and run new wires if you have to, its very important that electrical is right first. mechanical problems can sometimes be the hardest to diagnois, but there are ways of testing certian issues

*CELs and LIMP MODE, any number of things can throw you into limp mode and you definatly won't have vtec. most likely if you have a CEL fix that first then worry about VTEC. CEL can be a great indicator as to whats going on, and that light is lit for a reason. even when people say, "i have a CEL but thats a different issue" fix that FIRST, then worry about vtec. many codes that are set have alot to do with why vtec isn't working. and if your car is most definatly not acting right take apart the dash and check that your CEL light is not burnt out. it should light up when you first turn the key on.

*VSS/ SPEEDO if your car loses its speed reference vtec will not engauge. the ecu will see it just as if you were sitting still reving the engine, no vtec

*TACHOMETER i have seen a case where there was a problem with a persons tach, and i don't know where the wiring problem was, but if the ecu doesn't have a tach reference , then how is it going to know when you reach proper rpm.. exactly

*OIL, if you don't have the correct oil presure no vtec: possible causes: dented or damaged oil pan (as members have said before) , not enough oil, or oil is so old and crappy it is thin as water

*VTEC OIL PRESURE switch, The vtec oil presure switch is what feeds back information the the computer to tell it wether or not the opening of the solinoid has alowed high presure oil into the vtec oil gallerys. Once the solinoid opens oil shoud presurize the vtec oil ways pushing the locker pins into place while the oil presure sensor right next to the vtec solinoid feeds back info to the ecu.

*TEMP, the cars coolant temp needs to be at a certian temp for vtec to engage, if any of your temperature sensors are screwed up that is another possibility to look into

*VTEC SOLINOID GASKET/screen, i have heard and seen many cases where a cloged or dirty screen that is part of the vtec soliniod gasket caused vtec to not engage or be intermitant.

*THROTTLE POSITION, if your throwing a code for the TPS being bad or wacky this can also cause intermitant or no engagement, from my expermiments, whether vtec engauges or not is throttle position dependent.

Testing the mechanics of VTEC

*You want to check are that you have the appropriate oil presure at head when approching the rpm vtec engauges. I have seen motors where their just wasn't enough oil press and it doesn't throw any CEL but vtec just doesn't work and you hit the 6500 rev limit. The way to check is take the 10mm bolt out of the head that is on the front left if you are facing the motor. This bolt gives you access to the oil way of vtec, this is the same bolt that you remove to do the air presure test listed below. But anway you need to get a gauge that screws into the oil port. Now from here you have two choices. once you have the gauge installed you can either raise the car up and run the car in gear in order to simulate the speed so the vtec solinoid will open and then measure the presure OR you can disconnect the 1 pin connector from the vtec solinoid and aply batery voltage tot he solinoid in order to open it so oil can/should flow into the vtec oil gallerys. The test has to have the motor reving at least up to if not beyond 5000rpm in order to get an accurate oil reading. now what ever way you shose to get the solinoid to open with the car runing is up to you but at 5000rpm you should read a minimum of 60 psi of press at that port. if you do end up having enough oil press i would investigate a bad vtec oil presure sensor. Also not having enough oil presure can also account for "Late" engaugement, where you reach the apropriate press after the preset engaugement point and then the ecu alows vtec to engauge because the required oil presure has been met.

*Secondly you want to make sure that your solinoid is opperational, take it off and using a 12 volt source and a ground make sure that the solinoid operates quickly and smoothly when 12v is applied. this is the valve and if it isn't working vtec won't either

*Third if all else fails you can check that vtec mechanics work by using air presure(this test should then be followed up by the oil presure test) Take off the valve cover, take the plug out of the front of the head next to the header, either find a fitting that you can adapt your air hose to screw in the head or get a blow gun with a rubber tip. with another person you have to block the bleed hole on the 5th cam cap and while applying 40-60 spi of air presure , slowly crank over the motor using the main crank pully and watch to see that all 3 rockers lock togther and start to follow the middle lob, the VTEC lob. you may even hear a tiny click as the pins in the rockers lock the 3 togther. also you will be able to tell that the vtec lobe is being followed as the lift or how far the valves are pushed down is much greater. with the appropriate air presure and if everything is workign corectly every valve should be following the vtec lob. make sure that you have a good air compresor that can keep up with keeping a presure of 40-60 psi. if you don't have luck try raising the presure a littlbe bit, but i wouldn't go much hiogher than 80 psi.

once you have verified that all the maechanics are working : vtec solinoid, oil press, and valve assembly then you can move from there and see where the problem lies in wiring.

Other Info

things i haven't seen but are possible are, a faulty vtec solnoid, vtec oil presure sensor, and if your ecu is not detecting the RPM signal.

more vtec presure switch info: the vtec presure switch is jsut that , a switch , its on or off deppending on the oil presure. the ecu sends out about a 10v signal from 1 pin and runs it thru the presure switch back tot he ecu. if the presure is to low the switch stays closed and the ecu "sees" this by the 10v returning, after the vtec solinoid opens the ecu is expecting to see that the switch is opend by the oil presure and for its 10v feed back to disapear.
THE JUMPER WIRE THEORY:if you just jumper the wire your simulating a switch that never opens, on the flip side however if you just disconnect it i think the ecu is smart enough to know that before the engaugement point it wasn't "seeing" its 10v feedback so it throws a vtec malfunction. doing some testing you can get a multimeater: remove the 2p connector from the vtec presure switch , measure voltage with the ignition on between the two pins on the plug you should measure about 10v, this will indicate the wires to the ecu for the vtec presure switch are good, then turn the key off and measure for continuity between the two terminals on the vtec presure switch. seeing as this is a switch its natural state is closed you should measure close to no resistance thru the switch. now this info just means the switch is good if you read continuity thru it but that doesn't mean that the switch is opening when it is supposed to. i would investigate the presure switch further if the oil presure tests are done and found that the correct oil presure is indeed there.

also where you car is hitting its rev limiter can give away even more information, if you can only rev to 6500 and then hit a fuel cut then your not in limp mode but one of the requirements for vtec to engauge has not been met.. such as temp, oil press speed, etc..

IAB solenoid activates on a P13 (91-96) at 4600, and 4900 on a P5M (97-01)
VTEC solenoid activates on a P13 (91-96) at 4900, and 5200 on a P5M (97-01)

but if you car is only reving to (i think limp mode if 5000 rpm) then you have something seriously prohibiting the car, and most likely almost definatly your CEL should be on, and like i said fix and present codes befor eyou worry about VTEC.

and NO vtec does not engauge if you sitting still in your car and reving it, the secondary runners will open up, but the vtec soliniod will not open.

which brings me to another point, part of what makes vtec work well is the fact that right before the secondary cam profiles engauge the secondary runners in the intake manafold open up to accomadate the engines greater demand for air flow when in VTEC. some times there maybe something wrong with the wiring that tells the IAB soliniod to remove vacume from the diaphram that holds them closed. If anything is wrong with the IAB system then that can cause vtec to feel like it is not engauging. The Iabs are rpm dependant only, and the do open if you reving the car in neutal. THe Iabs are held closed when the car is idling by vacume and continue to be held closed by vacume stored in the small canaster under the intake manifold so you will have vacume to the required rpm even at WOT. With key off and no vacume the IABs open due to a spring. so once vacume is removed they just go to their rest state which is open.

Wiring info
credit to jdmlude_dude ::check here for more info

There are 2 wire tha come out of the vtec pressure switch, one is hot and goes to pin D6 and the other can just be grounded off on the motor or on the chassis

A4 = Vtec Solenoid
D6 = Vtec Oil Pressure Switch

if you take the ecu and look at the pins as if it were in the car, say you lay it on a table with the top facing up and you look as the pins, the "A" pin numbers will start on the very right, Example:
Top side w/ the sticker
l --------------\/---- -------------- -------------------\/-- l
l l oo . . . . . . . . o ll . . . . . . . . ll oo . . . . . . . . ooo l l
l l oo . . . . . . . . o ll . . . . . . . . ll oo . . . . . . . . ooo l l
l -------------------- -------------- ----------------------- l

A fellow user also alreted me to the fact that sometimes even if everything else is 100% even wiring the ECU pins may not be making contact. so make sure that you check that your using the correct pins if you wired vtec in and make sure they are the correct ecu honda pins and none are opened up at all.

just a last note, i haven't covered ever possible cause in this thread, but im pretty sure 90% of people problems can be fixed or majorly narrowed down by going thru everything i have talked about. I aam always here to try and help people out, but don't post and ask for help if you haven't already tried basically everything here, or you are confused. This thread is based off of information i gathered and read about and is here for you to learn from and help yourself. i can assit but can't fix everyones problems.

G23 Basic Build:


This will help those who are looking to do the swap themselves or at the very least show the growing support for moving into an H or F series motor for aftermarket or engine replacement.

**Old 1FunRyd forum: ... .php?f=271

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