Lexus LS 460L- Huge knocking/ Hesitation while driving

M.Yasir · May 22, 2021

Hi All,

So yesterday i was driving normally, stopped at a gas station to fill up the tank, after filling up made reverse and experienced noticeable knocking, so i thought its ok it will go away

Then put in drive mode and moved further from the gas station connected into the highway and tried to go over 60mph and huge knocking/ car vibrating all over the place!, full gas pedal on the floor but the car is lethargic

So kept on driving at 60mph and stopped at another gas station on the way 12 miles from the 1st gas station, there was a small garage, the guys checked with OBD scannner no codes all clean as there was no check engine light

Next step the garage guys did was to open the spark plug it was as new as it can be, so no clue what happened all of a sudden

I should mention that before filling the tank my fuel was super low

Any ideas, please advice what would be the initial diagnostics or rather manual diagnostics, from where to start

Lexus LS 460L

Model 2007

ODO: 134,375 miles

dcfish · May 22, 2021

Sounds like air /fuel mix. Does the car idle OK ?

Bykfixer · May 22, 2021

I'm thinking two things. Possibly bad gasoline. As in water in the gas tank you filled it from. It happens. Rarely but it happens. Perhaps it was a lower octane than stated. That could cause pre-detonation.

But my first suspicion is raised by the comment the car was super low on fuel. Over time things settle out at the bottom of the tank and if you sucked up some of that garbage into your fuel system it could be a clogged fuel filter or injector(s).

The knocking could have been valves screaming for mercy while being starved for fuel. But that normally would have been been a rattling or pinging sound not a knocking sound. Although my work truck valves do make a low pitched getting ready to explode rattle sound on cold mornings.

Has anybody checked to make sure there is a proper amount of oil in the engine?

Bottom line if you have never let the car get low on fuel until now it could be as simple as trash in the fuel system starving the engine. One would think the engine misfiring would cause a misfire code though.

dcfish · May 22, 2021

Yes, All of the above ^^^Let us know what you find please.

DarcGable25 · May 22, 2021

10 hours ago, dcfish said:

Sounds like air /fuel mix. Does the car idle OK ?

I don’t know about anyone else but I have a 2007 LS 460 and I put 87 octane in there once and it was knocking but once I put the super in my car I don’t put anything else in my car and I haven’t had a knock yes it cost more but it makes my car rides better and that’s with the car specifies for you to use

M.Yasir · May 23, 2021

16 hours ago, dcfish said:

Sounds like air /fuel mix. Does the car idle OK ?

Yes car idling is ok but you can sense the missing by the vibration on the steering wheel, very minor though

15 hours ago, Bykfixer said:

I'm thinking two things. Possibly bad gasoline. As in water in the gas tank you filled it from. It happens. Rarely but it happens. Perhaps it was a lower octane than stated. That could cause pre-detonation.

But my first suspicion is raised by the comment the car was super low on fuel. Over time things settle out at the bottom of the tank and if you sucked up some of that garbage into your fuel system it could be a clogged fuel filter or injector(s).

The knocking could have been valves screaming for mercy while being starved for fuel. But that normally would have been been a rattling or pinging sound not a knocking sound. Although my work truck valves do make a low pitched getting ready to explode rattle sound on cold mornings.

Has anybody checked to make sure there is a proper amount of oil in the engine?

Bottom line if you have never let the car get low on fuel until now it could be as simple as trash in the fuel system starving the engine. One would think the engine misfiring would cause a misfire code though.

Yes the fuel was very low when i filled in and i also think the same that some waste/ garbage is sucked up in the fuel lines

Engine oil is absolutely fine

This is the problem, i have been into these situation many times when the fuel was super low and i managed to reach the gas station and filled it up and there no problems, but unfortunately this time it have cause a disaster

Strange thing is why no check engine light? this is my worry and brainstorming that why the ECU is showing that engine fire is perfect

Bykfixer · May 23, 2021

A common misconseption with the check engine light that began as something called "malfunction indicator lamp" as its purpose is not to say "pull over now before your car dies", but is intended to point out there is something amiss in the anti-pollution performance aspect. There's some safety stuff thrown in these days with anti lock breaks and traction controls too.

My wife called me one day on the way home from work to say the van was running weird. I checked it later that evening and replaced the plugs and distributor cap. It was misfiring somewhat but no CEL. Misfiring enough to be obvious. A few days later she calls to say it was running bad again and the CEL was flashing. I had not changed the spark plug wires and those things had begun to stop working proper. The misfire had become pronounced enough to lower the fuel economy and that triggered the CEL, not the fact that 5 out of 6 cylinders were struggling to keep going.

So even though your car is not running in a normal manner, it must be running within spec of your pollution control system.

M.Yasir · May 26, 2021

Well it looks like 2 of my ignition coils are busted, and more surprisingly i came to know that the GCC specs car is a little different and the American specs car ignition coil wont fit!! wasn't expecting that at all

Its being replaced now and lets see what will happen will report back

On 5/23/2021 at 3:42 PM, Bykfixer said:

A common misconseption with the check engine light that began as something called "malfunction indicator lamp" as its purpose is not to say "pull over now before your car dies", but is intended to point out there is something amiss in the anti-pollution performance aspect. There's some safety stuff thrown in these days with anti lock breaks and traction controls too.

My wife called me one day on the way home from work to say the van was running weird. I checked it later that evening and replaced the plugs and distributor cap. It was misfiring somewhat but no CEL. Misfiring enough to be obvious. A few days later she calls to say it was running bad again and the CEL was flashing. I had not changed the spark plug wires and those things had begun to stop working proper. The misfire had become pronounced enough to lower the fuel economy and that triggered the CEL, not the fact that 5 out of 6 cylinders were struggling to keep going.

So even though your car is not running in a normal manner, it must be running within spec of your pollution control system.

Cannot fully agree with you with the word "anti-pollution performance aspect", its not only pollution, as per my understanding the check engine light tells you that there is something wrong and you "should" look into it which is critical for the car and yes of course not to pull over

Pull over or not, in 07 Lexus it does sometimes say that "park your car in a safe place immediately and call your dealer" even if the car is running what i have experienced with this message that if you still keep on driving it will eat up all other associated components

For example in my Lexus there are many other codes popping up for the seat heating/ cooling sensors; rear ac sensors but those are not throwing the CEL light since they are not considered to be critical isn't it?

On the other hand if there is a problem with your combustion it will throw or at least it should through a CEL; or maybe a problem with your TCM it should throw a CEL,

Bykfixer · May 26, 2021

Note I said "began as" malfunction indicator lamp for pollution controls and added "thrown in" regarding safety items.

If it's flashing you should stop as soon as it's safe to pull over.

Codes mean something is not functioning within a given peramiter like say the o2 sensors have a spec for volts and if the computer reads the o2 sensor voltage is higher or lower it sends a code. That code may light the check engine lamp. If the a/c is not working at a given peramiter such as air through the ducts is 80 degrees although it is "dialed" to be at 50 degreees that won't light the check engine lamp. That does not affect safety or pollution output.