thetunster

I need help if possible. I have a 2001 Lexus GS430 and its pulling up a code P0300 random miss fire code and VSC light is no. I was driving one day and the car completely stopped on me while i was driving. After I tried starting it, it did not crank over until a few tries. When its starts the engine is super loud sounds like a huge banging and popping noise. It would die immediately or stay on for 3-5 seconds then it dies. After i replaced the plugs it stays on but idles rough and the engine is loud. Below is what i have done replaced and serviced to the car.
What i have done so far to the car

New battery, Replaced Timing Belt, Water Pump, Tensioner, Pulleys, Valve cover Gasket, cam seals, crank shaft seals, Spark Plugs, all 8 coils, replaced driver side of the VVT OCV Solenoid sensor. Its getting frustrating and im about to just give up.

Mr Jokster

iTrader: (8)

Well, you've done the electronic part. I say begin to focus on vacuum issues and/or fuel issues (injectors). Search around your EGR valve for clogs or leaks This is to start with the cheaper stuff. Next in line would be crankshaft position sensor and o2 sensor issues. Worse case and next in line would be bad cats, bad exhaust valves or bad computer. Highly doubt it would be that bad though.

Try resetting the the code and see if that helps. IIRC, resetting a code for sensors would cause the computer to start with default sensor settings and would allow the car to run "ok" for a short while before reverting to your current status which would be due to it now reading true data from the sensors.

kevin3344

How many miles? Like Mr. Jokster said focus on your vacuum or fuel those have been the only times my GS400 has shut off...that and a throttle body but you would know if that went.

One other item to note: it could be a fuel pump. Happened to me last year, felt like the car wasn't getting enough gas. Dealer did a fuel pressure test and that confirmed it.

bjamesr

I started the timing belt everything thus far ha been good ,as of now i can't find anything on a DIY to change the crankshaft seal as well as camshaft seals. wa sonly planning on doing the timing belt but with this already off and a known oil leak trying to do it all.
I
2003 GS430 3UZ-FE

caverman

How about the coil connectors? Sounds like that's about the only thing electrical you didn't mention. I'm going through the same thing with my GS300 right now. I got the P300 plus the codes for about 3 cylinders that were missfiring. All of the research I've done is pointing to the clips. I have a set on order and hope to have time to work on the car next week or so. I got four for $24 dollars shipped but I would go ahead and do all eight while you're at it. At this point you've replaced just about everything else and while you can get to them you might as well do it for peace of mind if nothing else.

bjamesr