I have a 2001 rx300. I had a knock sensor go bad. I replaced it and now have a p0302 misfire. I changed the plugs, switched the coil and injectors around and still not working. At speed the light turns off, but at idle and lower speeds it flashes. I dont know what else to try. Any advice would be appreciated

 

This is for cylinder #2 ... [your in luck as it is the one n the front .. radiator side ..] towards the passenger.

Plugs should be changed around 110K miles with OEM [you can try others but if you are having issues, stick with the reliable]. Share with us the swap procedure you did and checked.

Also look for loose vacuum lines .. the vehicle is old and reconnecting hoses some times have a problem. Also look at the plumbing of hoses .. a member recently reported a wrong hook up. All these issues arise after a repair is done. So retracing the footsteps would help.

Salim

 

I changed all the plugs and swapped out the coils and injectors from different cylinders. It runs fine when at speed but idle is rough. When at speed the engine light stops also. When I pull the #2 coil wire it doesnt change how it runs (same with injector wire)

 

Which plugs did you install? NGK/Denso irridiums?

Vacuum plumbing?

Salim

 

So I changed them with cheaper NGK plugs. I did a compression test on #2 #4 #6 an#2 is 75psi, #4 is 125, and #6 is 170. Plugs are all really black. Should I assume headgasket?

 

You have diagnosed your problem. For the question you ask, you will need to do more investigation, I would suggest visit a mechanic who can perform various tests and confirm that the problem is above the piston or not.

Salim

 

Sorry for taking a bit to respond. With the p0302 and p1305 code plus 2 cylinders running low compression am I right to thing head gasket. It does give off some white smoke on cold start also

 

A good mechanic will be able to confirm by lowering a camera, doing compression leak down tests and even oil-coolant check. The bad compression can be due to rings as well. So your conclusion may be right but it might be better to get confirmation by testing.

Salim