Hi everyone. Newbie here. I recently purchased a 2000 lexus gs300. It developed a check engine light shortly after. Then the vsc and vsc trac off lights came on which i understand happens after the cel has been on. I have had the codes read and replaced the MAF. Which obviously wasnt the answer if the lights are back lol the check engine is solid, not flashing.
Ive had my boyfriend check for vacuum leaks, etc. After replacing the MAF lights went away after reset only to come back yesterday. It drives GREAT. I officially am addicted to this model for the smoothness and durability of the engine make. Love it. I DONT want to just throw parts at it as it could be a long list of ANYTHING... spark plugs, wires, coil packs, gas cap, o2 sensor... im replacing spark plugs next. Ive done fuel injection cleaner (chevron). The codes honestly lead me nowhere as it pointed to the MAF. Codes were random misfire, running lean, misfire on cylinders 1-4. My boyfriend is able to work on it for me but not sure what needs to be done. Should i have the battery checked? Next up is clean throttle bottle, clean intake with seafoam and new spark plugs and check wires/coils. It ONLY misfires at idle, cold start or when at a stop sign. It doesnt misfire when the weather is warmer... other than the misfire at start, it drives perfect except slight hesitantion at 30 mph. Ive seen this issue on this model on other sites so ANY feedback is helpful. Thanks a lot.

 

First off, welcome to Club Lexus

Also, be sure to use the search function with the codes you got, this car has been around for 20 years and all the answers are here for you

As for the codes, please post them when asking questions, thats the only way you can get input. Definitions are shared with different codes, but can be unrelated, so the actual code is important.

As for your problem, I'm willing to bet its a bad o2 sensor, but again, need the codes

 

Ok thanks for the input. I appreciate it. Codes are as follows (ill edit my post if i can to include them)
P0171 system too lean bank 1
P03000 random misfire
P301-P304 cylinder 1-4 misfire detected
P0100 mass or volume air flow circuit
P0110 intake air temperature sensor 1 circuit

 

ok, so don't think its an o2 now. Looks as if more air is going in than being read by the ecu. Was a good idea to check the vacuum, but I say focus around the intake, specifically under the resonator and the "accordion" part. Its right over the exhaust manifold and the heat, in time, makes the plastic brittle and will crack causing more air to get in after the MAF sensor.

 

Like mentioned above, check the accordion (in front of throttle body), also while engine is idling you can spray water to check for vacuum leaks (when leak is sprayed the engine will run rough)...Lean codes can be a pain to diagnose sometimes. Since you said its worse at idle this does point to a vacuum/unmetered air leak causing the lean condition. Just go over all air intake tubing and vacuum/breather hoses.

 

Hello I recently ran into the same problem the P 0300 code which was a random misfire. I dug deep an removed the throttle body an replaced spark plugs an wires all six. Also took the opportunity to redo the valve cover gaskets, and when i put it all back together that wasn't it. I then took it all apart an comes to find out the wires that fed the three coils had major deterioration and were arching which caused the random miss fire. Check for continuity between the two contacts at the end where they connect to the coils if there is then you have a short. I redid the wires an now its up an running again.

 

Like this ones,

Check your coil plugs electric wires.

 

stop using those fuel injector cleaner. It's bad.

 

100% agree with you Mr Jokster.
Check that air intake hose like this one on eBay, item number 262386938314.

 

I at first tried to only repair the tips cause the clips were brittle then when I put it all back together it still gave me the fault code so I redid it again an took the harnes all apart an this is what I found

 

Buenas tardes, soy nuevo en el Grupo, tengo un Lexus GS 300 Y quisiera saber Si Me pueden Ayudar, hijo Para Que Los 3 Botones Superiores Que Tiene el auto, al presionarlo Enciende Una luz roja