I'm currently working on a 1999 Lexus rx300. The engine is being de-rated by the ECU and can't go over 40mph, or half throttle. Only DTC's stored in the computer are p1300, 1305,1310,1315, 1320, 1325 which are all misfire codes, But the ECU is causing the misfire. I pulled all the coils and plugs, Replaced the plugs and one coil on #5 because of how it looked. Another reason I know it's not a "regular" ignition misfire is because in the driveway if I brake and throttle at the same time it doesn't skip a beat (no misfire under load) From what I've found, it's possible that the OCV valves, or the IGF circuits can cause this. But I am unfamiliar with Lexus/Toyota systems. If anyone could help point me in the right direction or provide ignition wiring diagrams, it would be much appreciated.

 

Welcome to the Club.

After replacing the coils, did you take attempt to take vehicle for short drive, to see if any other codes popped up, and if so how far?

 

Those are not misfire codes, but rather no IGF signal codes. Our coils should send back 4 pulses on the IGF wire for every 1 pulse on the IGT wire. While I doubt all 6 of your coils have failed, I can tell you your VVTi OCVs can not cause this problem, you definitely have an electrical issue.

Check the service manual here: http://bio.souz-96.com/Lexus/RX300_R...iagnostics.pdf on page 98.

http://bio.souz-96.com/Lexus/ has a pretty good collection for the RX300.

 

Thank you very much for the diagrams now we have a fighting chance!