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.

[Torrance25]

On 1/1/2024 at 10:48 PM, dtran18564 said:

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.

I’m having similar issues as well but my car still has full power. Just misfiring on cylinders 3,5,6&7. Did you ever fix your problem?

[dtran18564]

I finally found my problem was caused by the timing belt jumped 2 teeth after opening up the left and right timing belt covers to check for alignment. I was able to align the timing belt from the top opening after a few tries.

All the codes were cleared afterward and the car was back to normal.

[Torrance25]

4 minutes ago, dtran18564 said:

I finally found my problem was caused by the timing belt jumped 2 teeth after opening up the left and right timing belt covers to check for alignment. I was able to align the timing belt from the top opening after a few tries.

All the codes were cleared afterward and the car was back to normal.

Man! How did you realign it? You didn’t have to take the fan and all that off?

[dtran18564]

I had exhausted my search for solutions until I came to this thread as a last hope just like you.

I had finally kept going back to this you tube and it convinced me that the cam shaft timing re-alignment can be done w/o taking everything apart, note that at minute 3:05 he said to "pop the tensioner out", this will give you the slack on the belt to slip it off the camshaft sprocket, rotate the camshaft and then slip the belt back in.

It's important to mark the belt in relation to the sprockets, so you know number of teeth you shifted because when you put the tensioner back it will move everything back to proper places. I had to slip it on/off two to three times before I got the feel for it.

The tensioner can be accessed from the bottom, but when you put it back you need a little longer bolts to start engaging the thread because the plunger on the tensioner is now extended. One option is to exchange the bolts one at a time with longer bolts and slowly back out the tensioner  without taking it out completely.

Rotating the camshaft can be challenging, I managed to use both socket wrench for one direction and channel lock for the other.

Knowing that this can be done and trust yourself that you can also do it!

My 99 LS 400 at ~144 K miles with original timing belt was still running great until the drive belt ripped few strands on the freeway and it had a sudden jerk that caused it to miss fire and resulted in all these codes. 

If you plan to keep the car and not ready for a timing belt replacement, then knowing that this can be done.

I hope this helps. Best of luck! 

   

 

[Torrance25]

1 hour ago, dtran18564 said:

I had exhausted my search for solutions until I came to this thread as a last hope just like you.

I had finally kept going back to this you tube and it convinced me that the cam shaft timing re-alignment can be done w/o taking everything apart, note that at minute 3:05 he said to "pop the tensioner out", this will give you the slack on the belt to slip it off the camshaft sprocket, rotate the camshaft and then slip the belt back in.

It's important to mark the belt in relation to the sprockets, so you know number of teeth you shifted because when you put the tensioner back it will move everything back to proper places. I had to slip it on/off two to three times before I got the feel for it.

The tensioner can be accessed from the bottom, but when you put it back you need a little longer bolts to start engaging the thread because the plunger on the tensioner is now extended. One option is to exchange the bolts one at a time with longer bolts and slowly back out the tensioner  without taking it out completely.

Rotating the camshaft can be challenging, I managed to use both socket wrench for one direction and channel lock for the other.

Knowing that this can be done and trust yourself that you can also do it!

My 99 LS 400 at ~144 K miles with original timing belt was still running great until the drive belt ripped few strands on the freeway and it had a sudden jerk that caused it to miss fire and resulted in all these codes. 

If you plan to keep the car and not ready for a timing belt replacement, then knowing that this can be done.

I hope this helps. Best of luck! 

   

 

This is awesome!! Gonna try it out. I have a few questions for my understanding going into it because I don’t want to buy a new engine lol.

 

what tensioner is that? Is it the serpentine belt tensioner?

 

when I mark the belt, do I need to turn that as well to make that line up with the new marks?

 

do you have a link to the new bolts you used?

 

where did you grab the sprockets with the channel locks? And the socket wrench, did you put it on the camshaft sprocket bolts?

[dtran18564]

No, it's not the serpentine belt tensioner, it's the timing belt tensioner (see pic)  The bolts are 12mm, don't remember the length but guess about 30mm long.

You need to rotate the crank to 0 degree and check for the camshaft sprocket notch line up (or close to ) with the line on the back plate for both sides, otherwise you need to rotate one more revolution for them to line up or close to it. If they don't line up then you have an idea how many teeth you are off.

Assuming you find out you are off by 1 or 2 teeth, then you mark the belt against the edge of the sprocket so you know number of teeth needed to shift for verification. You then slip the TB off and rotate the camshaft to the mark and slip the TB back on. The objective here is to line up the timing mark on the crank and the camshafts at the correct marks when the TB tensioner is reinstalled.

I used the socket on the camshaft bolts going clockwise and channel locks going ccw on the serrated portion of the camshaft (maybe using a rag to protect from marring the surface)

[Torrance25]

25 minutes ago, dtran18564 said:

No, it's not the serpentine belt tensioner, it's the timing belt tensioner (see pic)  The bolts are 12mm, don't remember the length but guess about 30mm long.

You need to rotate the crank to 0 degree and check for the camshaft sprocket notch line up (or close to ) with the line on the back plate for both sides, otherwise you need to rotate one more revolution for them to line up or close to it. If they don't line up then you have an idea how many teeth you are off.

Assuming you find out you are off by 1 or 2 teeth, then you mark the belt against the edge of the sprocket so you know number of teeth needed to shift for verification. You then slip the TB off and rotate the camshaft to the mark and slip the TB back on. The objective here is to line up the timing mark on the crank and the camshafts at the correct marks when the TB tensioner is reinstalled.

I used the socket on the camshaft bolts going clockwise and channel locks going ccw on the serrated portion of the camshaft (maybe using a rag to protect from marring the surface)

Ok thanks, what all did you have to remove? I don’t want to take too much Stuff off the engine

[dtran18564]

Two camshaft timing covers, top water hose, serpentine drive belt and bottom access to TB tensioner. Can't remember about the fan and alternator for easier access.

[Torrance25]

39 minutes ago, dtran18564 said:

Two camshaft timing covers, top water hose, serpentine drive belt and bottom access to TB tensioner. Can't remember about the fan and alternator for easier access.

Ok thanks!