Okay so A friend took his 5th gen prelude (98 SH) to a mechanic for an engine swap after he Hydrolocked the H22. He was gonna put in an F20B but after the mechanic removed the old engine he quit and said it was impossible due to the Crank Sensors not being on the F20B Yadda Yadda. So me and my dad took the job over.

-We have installed the F20B into the Car with the Stock TripTronic Tranny.

-I wired the crank sensor to an external coil H23 Vtec OBD1 Distributor as shown by Bustr's Guide on Prelude Forums.

-We reused the H22 Intake Mani so all the sensors would match except were using the jdm map sensor since I figured the old one maybe was fried by the water.

-After replacing the main relay being blown out and checking fuses the car starts up great and idles fine.

BUT if it stays running once it warms up the idle starts surging badly till the car turns off. Since I wasnt the one who removed the engine I have no idea if the vaccums are correct or not. I plan on going over them next I think all the sensors are plugged in. Any Ideas on what could cause this???

 

It's a common issue for honda motors. Any CEL's (like maybe the IAT, ETC, or IACV?)?

Anyways, do a search for: honda iacv fitv, and you should find plenty of pages that tell you how these two idle-control systems work together. Most of these pages will also tell you how to troubleshoot it.

--TJ

 

Found out the idiots who took apart the car mved the vacuums arund EGR was getting a direct vacuum lol, routed it to the solenoids and runs great now

 

Okay so the car is in limp mode not letting it rev past 3k rpms. Its throwing a code 9. I think its because I need a different ECU since the H22a one reads the crank sensors from the oil pump and I wired them to read from the Distributor and I heard they have different pulses.

I was wondering what ecu I can use for it, Its an OBD2a 99 Prelude AUTO. Can I used a JDM F20B OBD2 ECU? Does this bring about Immbolizer issues?

 

In my experience it is possible to use a USDM ECU with a JDM/OBD1 distributor setup, although it constantly flashes misfire CELs over certain RPMs.

That said, it might not always work. You're either dealing with that, or you screwed up the wiring. The latter is a distinct possibility.

In the long run maybe you can dig up a Prelude JDM ECU that works, the Accord one will probably give you some challenges of its own.

 

Yea I found a P5M F20B Auto Ecu with no Immbolizer OBD2a....THink that would work??

 

Why don't you just swap over the oil pump from the hydrolocked motor, if that is where the code is coming from?

I would stay away from JDM ECUs....I am not a huge Prelude expert, but with my Civic, I couldn't use the JDM ECU for a few reasons (i.e. JDM ECU looks for 1-wire oxygen sensor signal, etc).

I just swapped a JDM H23A VTEC blue-top engine and the swap went flawless. I re-used my CDM-spec H22 distributor, intake manifold with ALL sensors, and oil pump.

 

Oil pump had 150k+ miles so figured it was too risky to reuse.