2000 LS400 code p1346 p1349 p0300

[lexusls4]

So my 2000 LS400 started misfiring recently and it can go a week running fine and then all of a sudden it will misfire at every stop light. Car seems to run fine when going but whenever I hit a stop light it will usually start shaking pretty badly, then sometimes it will be still. Have got the code for random misfires and the cylinders 1,3,5,7. Along with p1346 p1349 with the VVT. I have replaced the spark plugs, the car ran fine for around a week then started misfiring again. just changed out the oil control valves and still is rough idle and shaking but very slightly. The car idles super low too when still. Along with a super strong smell of gas when starting the car and having it warm up too. 

[Jeremy M.]

Because you have multiple codes, you have a few different places you can start as far as diagnosing the issue.

If you want to address the fuel smell, check along the injectors for a fuel leak, and check fuel pressure at the fuel rails (the factory manual calls for 57 PSI). If you're smelling gas, it is likely leaking and causing a drop in pressure, which will affect the engine most at idle. 

You can also do a quick check for a vacuum leak along the bank of cylinders that are misfiring (driver's side of engine). You'll spray starting fluid or brake parts cleaner (make sure the label does NOT mention it being non-flammable) along the mating surface of the cylinder head and intake manifold, and listen for a change in the idle. If it smooths out while you provide fuel, you have an intake leak at your manifold gaskets and/or your injector o-rings.

If you have cleared the codes and the two VVT codes are coming back, start by checking oil level, then you have two paths to take. First, you can check the two camshaft position sensors and crankshaft sensor, because the correlation between these three sensors will determine the code being set. Attached are sections on the service manual for the sensor inspections. The other path to go on is to check the mechanical operation. If you are confident your new actuators are good (unfortunately you can't consistently rely on this with aftermarket VVT actuators, OEM is HIGHLY recommended), then you need to check your oil pressure to make sure you are getting 4.3 PSI at idle, and 43-85 PSI at 3000 RPMs. You will check you oil pressure by removing the oil pressure sensor and installing a manual gauge. If you have proper oil pressure, and your actuators are good, then one or both of the camshaft phasers are likely bad.

[paulo57509]

'98-'00 aren't susceptible to leaking ECU capacitors but it does happen.  It might be wise to pull the ECU and check.

There's a sticky here:  https://www.clublexus.com/forums/ls-1st-and-2nd-gen-1990-2000-183/

"All my crazy Lexus issues SOLVED!! (ECU-leaking capacitor)"

[dtran18564]

lexusls4: Have you been able to find the fix for the problem with "2000 LS400 code p1346 p1349 p0300"? I have a 1999 ls400 and currently having similar issues. I have opened the ECU but did not see any trace of leaky capacitors. Will try to look for vacuum leaks next.