hjl47

First off, let me say, great forum here! got alot of good info and help.

I have a 2002 LS430. 200K miles

it was ldling badly and lots of CEL. Had 0420 O2 sensor codes. and misfire on the whole driver side cylinder 1 3 5 7.

I replaced all spark plugs and did the DIY 02 sensor eliminator and wired that into the rear sensors.

After that, I was still getting 1349, so I replaced the OCV on the driver side. CEL was cleared for a bit, but came back on and then I got 1354, so I replaced the other OCV. Both OCV replaced w/ OEM.

So now I was getting flashing CEL w/ P0301, so I swapped the coil to cylinder 3 to test if coil itself was bad. CEL now was showing P0303 and P0304. which was strange as I didnt touch cylinder 4 coil. I bought all new original coils and replaced all 8, but now still getting CEL P0304 and P0303.

What else could it be? I replaced coils and plugs w/ oem denso and NGK

Could doing the DIY O2 sensor eliminator hack cause the misfiring? and if so, why would it go from just P0301 to P0303 and P0304 when transferring just the one coil?

Thanks in advance.

BradTank

No, I don't see how it could, if you are talking about the O2 sensor after the catalytic converter on the exhaust. That doesn't effect the ignition system, it's just a pass or fail for the converter mainly for the purpose of state emission testing.


My advice when you have a lot of codes being thrown and can't figure it out is to take it to a dealership and let them troubleshoot. They have the expensive scanners that can figure this out, and 1-2 hours of their labor is a lot cheaper than throwing a lot of parts. You can then decide to fix yourself or let them repair.

I honestly would start by looking at something like a loose ground somewhere. It just seems to be a lot of random codes and you've put a lot of parts into it.

hjl47

Thanks for the input. So speaking w/ a clerk at autozone, he suggested that the valve cover gaskets and tube seals could be leaking, causing oil to get onto the coils and plugs, causing the misfire. Does this sound probable or not really a common problem w/ the UZ motors?

911LE

Were the coils or plugs wet with oil when you replaced them? The valve cover gaskets and tube seals are definitely know to leak after time. Not really sure how it would cause a misfire though.