Hello,

I bought my kid a used 2008 Lexus GS350. Within days, P0430 and P0305 codes. I understand that the first code could be something with Bank 2 catalytic converter and the second code is Cylinder 2 misfire. An thoughts or previous experience?

 

Hello, congrats! I wouldnt worry about the catalytic code just yet. I would deal the with misfire code first. First thing I would do is remove the battery terminals, remove the spark plugs examine them if they look bad replace them with oem FK20HBR11 or authentic denso 3473 plugs. There are a lot of fake spark plugs on ebay/amazon so purchase from a reputable source. Also becareful when removing the clip harness plug on each coil pack as the tend to break. If the misfire goes away and you still have the catalytic code, then I would raise the car with it running have someone block off both exhaust ports with a towel and carefully inspect the whole exhaust system for leaks. A common issue is leaking at the mid pipes due to the tin covering, that should be removed as it only rots out by rusting the exhaust tubes.

Its very possible if a misfire isnt fixed, can destroy the catalytics. But these lexus oem are very strong and can handle a lot.

 

Thank you. I really appreciate your response. Last week when I checked the codes with a different code reader I never had the misfire code. Today after buying my own code reader that's when to my delight another code (the misfire one) appeared. The car has almost 300000 km

 

I dont trust cheap scan tools! Ive used some that have read tottally off, maybe our cars dont like them.

As for your sons GS, when you drive the car are you feeling a misfire? Also was the car parked for a long period, without it being driven sometimes when they are not driven they throw off random codes.

I would still do the basic stuff like examine and replace the plugs, remove and clean the throttle body, remove and clean the maf sensor, replace the water pump (very important at your mileage), do a transmission drain and fill atleast 2

 

Thanks, this is why I hate used cars. He better start getting better grades so he can get a good job in the future!

 

You can do the easy stuff that doesnt cost much, and it doesnt take much time. Like removing the throttle body and cleaning it along with the maf sensor, then put the fresh spark plugs. Later on you can purchase the water pump, there only $90 and require 3 hours worth of labour, there are videos online for diy. These cars are solid bullet proof

 

Well, got the CATs hollowed out as they were all plugged. Cylinder 5 misfire still there. So I changes all spark plugs, and swapped the coils. Still Cylinder 5 misfire upon cold starts. No more Cat codes, but always Cylinder 5 misifre on cold starts, rough idling too.

Any ideas of what next.....obviously things seem to be pointing to Cylinder 5. It was the spark plug that looked the worse compared to the other 5. Very black and carbon on electrode.

 

I would reinstall back all of the factory coils, since they were good. Im assuming you purchased aftermarket coils? The stock coils are very reliable.

You really should take the car to a mechanic you can put the car on a good scanner. Pay for 1 hours worth of diagnostics! Then fix the issue yourself. Plus you will save yourself the headache! All you are doing is guessing, and throwing money at it in hopes of a fix.

A misfire could be from a whole bunch of different issues. bad fuel injectors, power to the ignition coils, bad wiring, bad fuel etc.

 

1. All spark plugs were changed. Cylinder 5 plug was black. I didnt replace coils. Just moved them to different cylinders. Still misfire.

2. Another auto repair shop ran a compression test and cylinder 5 had 55 psi and it should be around 140 psi. Shop told me i needed to replace engine. They did no further diagnosis.

am i screwed?

 

55psi is pretty low, what is the car doing? Did they run a camera down that cylinder to see whats the issue? You can sell the car, or you can just drive it until the engine fully stops. You are looking at around 3 grand to swap out an engine

 

All they did was a compression test and told me I need a new engine. It generally only misfires on cold starts. Old spark plug was pretty black.

 

Wow sorry to hear. Must have been poor maintenance by the previous owners. These cars need routine oil changes to avoid long term issues like this.

How many miles does the car have?

 

It has 296000 km

 

That's actually about right. These engines are rated for about 300k miles before failure.

However IF oil change intervals and levels were routinely monitored for the life of the vehicle, it's definitely possible to squeeze out even more miles. Really depends on how the car is driven.