How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site. Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask Billy Your Own Question
Billy, Trainer/ Master Technician
Category: Car
Satisfied Customers: 3498
Experience:  Trainer 8+ years, master tech. 10+ years, SAE member
Type Your Car Question Here...
Billy is online now

Hilexus gs300 2001ramdom misfirep0300 p0305 p0306I

Customer Question

Hi lexus gs300 2001 ramdom misfire p0300 p0305 p0306 I have been getting these codes and have changed Plugs Coils Injectors and all 4 O2 sensors the car was converted to LPG by last owner I have removed the lpg as I felt it was of pure quality. ... The car has also been De catted... with spacers fitted to both no. 2 sensors I would greatly appreciate any help Kindest Regards Keith

Submitted: 2 years ago.
Category: Car
Expert:  Shantal-Mod replied 2 years ago.
Hello Keith,
I'm Shantal and I'm a moderator for this topic.
I've been working hard to find a Professional to assist you with your question, but sometimes finding the right Professional can take a little longer than expected.
I was checking to see if you had already found your answer or if you still need assistance from one of the Professionals.
Please let me know if you wish to continue waiting or if you would like for us to close your question?
Thank you,
Customer: replied 2 years ago.

Hi Shantal

No I have not yet received any response to my question. ..

I would appreciate it if you keep searching. ..

Many thanks


Expert:  Shantal-Mod replied 2 years ago.
Hello Keith,
Thank you for getting back to me and apologies that you have not received an answer yet. We have a range of Professionals online all the time. However specialties differ, and we are searching for the right professional to assist you.
Should you wish to close your question and reverse your charges at any time please let me know.
Thank you for your patience,
Expert:  Billy replied 2 years ago.
Hello Keith and welcome! I'm Billy and i will assist you with this. Feel free to ask if further info is needed.

My apologies for the delay, thank you for your patience.

Was the compression pressure checked on all cylinders?
Do you have a manual or auto transmission? if manual, was the flywheel replaced with a low weight performance flywheel?
Was the timing belt and tensioner checked (too loose, too tight, or even jumped a few teeth)?
Apart from the fault codes, what symptoms are you experiencing with the vehicle?

Kindly get back to me on these, so we proceed as necessary

Customer: replied 2 years ago.

Hi Billy

Thanks for your reply

Compression test has not yet been performed as I feel the car pulls to good... runs fine.. in fact there or no symptoms... driving just can't keep check engine light off...

Sometimes I car drive the car for 115 miles before the light comes on

other times its on after 30 miles

O the car is automatic with new ATF fuild (millers)

Timing belt done 30.000 miles ago.. by last owner so I'm unsure what has been replaced

possible just belt

Hope this information helps

Best Regards


Expert:  Billy replied 2 years ago.
Hello Keith,

Any additional details and info always help....

I would start by checking for compression pressure, and for any mild vacuum leaks (as most of the other checks are already done).

To give you an idea on the system:
A misfire is detected by monitoring the angular acceleration and speed of the crank and cam sensors. Whenever there is more acceleration or decceleration than permitted, the misfire code is triggered. The system also monitors at which exact moment this is happening to identify which cylinder is misfiring.

So it does not have to be an actual misfire event. Any irregularity with the engine rotation will cause this.

Kindly get back to me with your findings, or if further info is needed, so we proceed accordingly.

Customer: replied 2 years ago.


shall do....


Expert:  Billy replied 2 years ago.
Take your time, and get back to me with your findings, or if further info is needed.