Skip the auto shop - Our mechanics make house calls

Q: My car has several misfire codes and does not run properly.

asked by on

it was throwing the fault codes p0300, p0301, and p0305. so we replaced all 6 coil packs and spark plugs and the next day it drove great. but the day after that the car went into limp mode and we can't figure out why. we checked the coil packs, spark plugs, mass air flow sensor and we still can't figure it out we think it may be the crankshaft position senor or the injectors maybe we got a bad coil pack. i don't know so any help would be appreciated

My car has 117000 miles.
My car has an automatic transmission.

A: Hi there. What prompted you to replace thos...

Hi there. What prompted you to replace those particular parts? Did testing reveal a fault? This year model, along with its sister IS models, up to 2011 had a service campaign for cylinder misfires. The campaign did not cover the testing for the condition, but it did cover if the testing revealed results according to what was specified. Unfortunately, Lexus began phasing out this campaign several years ago and the 2006 model has been a casualty of this phase out. There are some things not related to the campaign that can cause your misfires and possibly lead to the "limp" mode you stated, how was the "limp" mode determined? Many times, the oil control valves for the VVT become worn or contaminated and begin to stick; I believe this is the case with yours as the misfires are all on Bank 1. Remove the oil control valve and see if it is pretty easy to move, if so then the filter may be clogged; this filter is located in the port where the metal oil line attaches to the valve cover. If it feels at any point that it may be sticking, then it needs to be replaced. You may need to clean the filter and reinstall; if there is no filter, it has to be replaced as this is what protects the oil control valve. I highly suggest a fresh oil change with the proper oil and filter and use only premium fuel; using regular fuel grade is what led up to the service campaign correcting carbon buildup on the valves and pistons. I suggest having a qualified technician perform an inspection to avoid replacing unnecessary parts. Your Mechanic has several available technicians that can assist you with a check engine light inspection.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: Hi. I have a 1999 Lexus GS 300 and I wanted to know if you use OEM parts?

Hi there. The parts team at YourMechanic has gone through a rigorous filtering process to select the brands that are best suited for your car. Our parts catalog has a list of approved brands for each type of car and...

Q: Rear brake light, and some interior lights don't come on unless I'm braking

Hello. Replacing the stop light socket with a new one should have solved the intermittent problem of the stop light not working all of the time. It is possible that when you tweaked the socket, it caused a short to...

Q: My car is overheating when driving instop and go traffic

Hi there, it sounds like you're on the right path; it's overheating because the fans aren't turning on. We know your thermostat and water pump are both operating, otherwise it would most likely be overheating all the time. You said...

Related articles

How to Avoid Back Pain in a Car
If you have back problems, sitting in a car for an extended period of time can be excruciating. Even without back problems, you could experience discomfort and soreness from...
What are the Car Pool Rules in Hawaii?
Hawaii is widely regarded as a land of vacation and relaxation, and as such, its scenic roads and routes are far better known than the state’s freeways. But, as with all...
How Much Does a Mechanic Make in Vermont?
Automotive technician jobs in Vermont have an average mechanic salary of $37k, with some mechanics earning a salary of $53k.