Hello everyone! My grandmother passed away and left me her 2006 SC430. It only has 40k miles. It wont pass smog. Shortly after getting it (it sat around while waiting for final papers etc) The check engine light, VSC and VSC OFF buttons came on. It was having issues starting and the battery died. We replaced the battery and the lights went away. We drove it 200 miles to get the engine computer to finish all the tests. When all the computer tests were done, it said it would pass smog (blue driver reader). Then the lights all came back on. I ran the check engine tests and it said misfire spark plug so i replaced all the spark plugs (genuine lexus parts). then i got the error cylinder 1 misfire detected, cylinder 2 misfire detected, cylinder 7 misfire detected. So i replaced those 3 coils (denslo) Car ran great for 1 day. now i get all these codes. (i will post a pic). Can anyone help??? I'm afraid i'm running out of thing I can do myself. the car has sentimental value and I hate to let it go.

 

Where specifically did you buy the parts? Do you still have the original coils?

 

Hello. I purchased the spark plugs from Toyota dealer and the coils from WalMart online. Yes, I have the original ones I took out.

 

Put the original coils back in see if anything changes. How long did the car sit meaning how old is the gas. If you keep getting the same codes one or both of the oil control valves could be gunked up or failing.

Any sign of rodent damage?

 

I know it seems desperate, but if you step back and take a deep breath. Misfire codes are usually easy problems to solve.

I agree with Lex2K that you should check for rodent damage. Trace the coil wires and see if anything is chewed up.

Take the coils off the misfiring cylinders and swap them with the coils on the cylinders across the engine. Drive around and scan your car again. If the misfire moves, then you know it is the Coil. If you bought new coils, then that is most likely not your problem.

How confident are you that the spark plugs were installed properly?

It might be better if you watch these video and you can see the steps to diagnose the problem. The first one basically covers what we already said. The second one is a more in depth look at the problem

 

It could also be the sc430 MAF sensor

 

WOW. This is a mess. First, Sorry for your loss. Have you checked for chewed wires? Mice are notorious for causing weirdness by chewing up a harness. And you have weirdness. Do me a favor and push the VSC button on the console. Does the VSC "OFF" light go out? The other VSC light is for now a non-issue that can be dealt with later.
So, lets talk about misfires. The P0300 is a general DTC to indicate multiple misfires from different cylinders. The other DTC's are for individual cylinders. The ECM uses the crankshaft position sensor AND camshaft sensor to monitor changes in the crankshaft rotation for each cylinder. The ECM (Engine Control Modul) counts the number of times the engine speed change rate indicates that misfire has occur. And when the misfire rate equals or exceeds the count indicating that the engine condition has deteriorated, the MIL (MIL = Malfunction Indicator Light a.k.a. Check Engine Light (CEL)) lights up. If the misfire rate is high enough and the driving conditions will cause catalyst overheating, the MIL blinks when misfiring occurs. Have you seen the check engine light blinking? Hint: When codes for a misfiring cylinder is recorded repeatedly but no random misfire code is recorded (P0300), it indicates that the misfires were detected and recorded at different times. Not the case here but it is still good info for others. Inspect wiring from the ECM to the coil packs. Check everything but find the crank and camshaft sensors and inspect that wiring even though I do not think that is the problem though because if it was, I would expect more random misfires than just 1 and 2. I am wrong everyday though about something. Check the "Injector" wiring. The two most forward pistons are 1 and 2. 1 being pass and 2 being drivers. Check everything you can find especially to those two cylinders. I hope you find something because the list of things that can cause this fault is long. This is what my 02 Volume 1, Page 05-74 says for "Diagnostics".
Open or short Engine wire.
Connector Open.
Vacuum Hose connection.
Ignition System.
Injector.
Fuel Pressure.
Mass Air Flow meter.
Engine Coolant Temp sensor.
Compression Pressure.
Valve clearance.
Valve timing. PCV Hose connection.
ECM.

Good luck Sir.

Paul

 

we have used the old gas up several tanks ago. i haven't noticed any rodent damage but I can certainly look around...

 

my friend who is a mechanic helped with the spark plugs. i did the coils. I will watch the videos, thank you

 

Try using Seafoam or Marvel Mystery Oil in both your oil and gas. Engines that sit too long tend to have problems like this. You might have sticky injectors and/or VVTI controls.

 

if you ran the old fuel through the system might be good to change the fuel filter also? Have you washed the engine bay? (this could be an issue also)