Joined: Jun 2018

Posts: 1

Likes: 0

I have a 98 Prelude SH with issues and I would appreciate some fellow gear heads to weigh in on the fix. Here is the problem... throwing P0304 and P1399. I recently bought the car, when the codes first showed, I did the easy things first. I pulled all the plugs and wires and replaced them. Along with the dizzy and rotor. Noticed that the plugs had not been changed recently (could tell due to their condition), no oil or residue on them, just showed signs of heat. Nothing “unhealthy” but definitely old. Tested the resistance on the original wires and didn’t show any issues, but replaced them with new ones anyway. Put everything back together, started it up, cleared the history from the ECU and went for a spin. Everything looked great, or so I thought. A couple days later had the same codes pop again (P0304 & P1399). So I pulled the fuel rail and the intake manifold along with the EGR plugs and cleaned the intake manifold. Put everything back together and did a Sea Foam treatment. Again, took it for a spin and everything cleared. I don’t have misfires anywhere else in operation other than at idle. This morning, got in the car to head to work and could feel a misfire at idle. Sat for a second and, what do ya know, the engine light started flashing again. I didn’t have time to run the codes this morning, so I parked the car and took the Taco in to work. When I get home today I’m going to grab a new fuel filter (because I seriously doubt it has been changed in a while), and I’m going to pull the fuel rail and switch #3 and #4 fuel injectors to see if the code switches from a P0304 to a P0303... if there is anything that I’m missing here, PLEASE let me know. I appreciate any help I can get. If I can supply more information to help with narrowing this down, let me know.

Joined: Dec 2008

Posts: 12,028

Likes: 5

Joined: Sep 2012

Posts: 718

Likes: 24

From: Kuopio, Finland