I have a question for anyone who might know the fix:

I recently purchased a 1998 Prelude from out of state. The last owner swapped the engine for a JDM H22A motor and used an OBDII->OBDI conversion harness with a P13 ECU. I live in PA, and in order to pass inspection/emissions, it needs to have an operating OBDII ECU that tells the emissions machine that everything's working.

I installed an OBDII Prelude P5M ECU, and now whenever I run the engine, the check engine light comes on and I get 5 codes: one that says there was a random misfire and one misfire code for each cylinder.

Originally from Honda, the 1998 Prelude's Crankshaft Position and Top Dead Center sensors are located behind the crank and the Cylinder Position Sensor is in the distributor. The JDM H22A has all three of these sensors in the distributor, just like the US's OBDI H22A1. Is this the source of the problem, or is there something else that's at play?

 

Anyone have a similar issue or have any info?

The ECU believes that there is a misfire if it does not see the crank's speed increase after it told the spark to fire. The ECU measures the speed of the crank by counting the miliseconds between each pulse from the CKP (crankshaft position) sensor.

Since my car has the JDM distributor with the CKP inside of it, I'm wondering if leaving the distributer turned after advancing the ignition timing would affect the timing of the CKP pulses. If so, this may make the ECU think that there was a misfire and cause the check engine lights.

 

By the way, I answered my own question about seeing if turning the distributor would resolve - no, it won't. The CKP, TDC, and CYP sensors are all built into the distributor on the H22A, and so read from the same axis. Turning the distributor changes the axis overall, but it does not affect the relation of the CKP sensor to when the spark is told to fire. The timing from the CKP is the whole reason why the ECU is thinking that there is a misfire.

 

You need install the USDM oil pump housing and sensors. For whatever reason, the sensors in the OBDI distributor do not play nice with the P5M.

 

Yeah, to use the P5M, that seems to be the only option to make the ECU happy.

Whoever designed the P5M over at Honda needs to join H-T and let us know how to make it work with the sensors in the distributor