Luder787

I have searched almost all forums but did not find anything that matches the problems I'm having, therefore I'm posting this message hoping someone will be able to help me.
I had a mechanic perform an engine and tranny swap on my 99 Prelude SH with a base engine and tranny from a 97 base prelude MT. We started the engine with my original ECU (SH engine ecu, 37820-P5P-L04) and the engine runs rough, misfiring (receiving codes 300, 301, 302, 303, 1399), we were thinking the engine is running too rich causing it to misfire. We installed a programmed obd1 ecu and the engine runs perfect. Thinking that I need an ecu that matches the 97 base engine so I bought one and had it flash with my immobilizer. We started the engine with the matching ecu (37820-P5M-L05) and the engine still runs too rich, misfiring. The only ecu that runs the engine perfectly is my obd1 ecu. I reside in California and needed an obd2 ecu to pass smog, I'm running out of ideas, help!

Additional notes: I installed new cap, rotor, ngk plugs and wires. Also the engine starts good and runs nice when engine is cold, but once it is warmed-up it runs rough, misfiring.

TypeT

of course it runs differently when SH and base ecus are different, have you checked your injectors are they clean and ok? some people take their injectors to ultrasound wash. if it runs odd with base ecu, check whole ignition - cap, rotor, plugs, wires... (you should renew those anyway if youre getting used engine)

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Honda Prelude 1997 2.2 VTI

Luder787

yea, I cleaned the injectors myself and I know they are working good since the car runs perfect with my programmed obd1 ecu with lots of power and makes 30 MPG.
O, I also updated my post to indicate my ignition parts are new.

TypeT

have you checked and adjusted your valves?

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Honda Prelude 1997 2.2 VTI

dontbuyprelude

clean your egr valve and ports

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David
01 SSM SH

93 d15 auto del slo gone and FORGOTTENexcept for a few memories....