jeronberna

Hey everyone, so i'm currently having a issue with a 1996 LS400 non VVT-i.

I'm getting a P0325 and a P0330 DTC for the knock sensor, I've searched through the forum's and come across some replies about how some people say it may be bad gas, and how it is very rare for the two to be throwing codes at the same time.

The car is currently also having misfires sporadically throughout the cylinders, no constant variable between any of them, aswell.

The car has a small exhaust leak, i'm not sure if any of this would be contributing to the misfires or the P0325 and P0330 code.

the current STFT and LTFT for Bank 1 is 19.5% and 0.0%
the STFT and LTFT for Bank 2 is 19.5% and 0.0% aswell.

Has anyone come across any of these issues? or have their own solutions for this problem?

I've replaced the old gas with premium gas, and seafoam'd the old gas until it was well below the line.

I put a little seafoam in the oil aswell, to hopefully clear up some of the upper engine sounds it had.

I've replaced the spark plugs, and spark plug wires.

The car was sitting for a good 3 years prior.

Here's some info it will help anything :
absolute throttle position 10.2%
Air flow rate 10.36 g/s
Ign. Timing advance 11.5 degrees
02s voltage bank 1 - 0.140v
02s voltage bank 2 - 0.210v
calculated load value 27.5%
STFT Bank 1 19.5%
LTFT Bank 1 0.0%
STFT Bank 2 19.5%
LTFT Bank 2 0.0%
Thanks to anyone for any help in advance!

Yamae

Both banks are having the same problems. Those simultaneous problems are typical symptoms of the failing Vcc circuit for the AD converters in the ECU. Unwanted ripples at the 5V DC line tend to cause those problems. I'd check the ripple voltage and the DC level first for the confirmation. Or simply replace those QAS capacitors as are explained in the FAQ's Electrical:.

jeronberna

Thank you Yamae! i'll be prying that ECU open today to take a look at those capacitors, hopefully i can visually see there is a issue. While reading the guide, i noticed every single 10u cap on the list is like 16w and 22w back order... you wouldnt happen to have a different suggestion for a 10u cap from something on digikey would you possibly?

Hopefully this will get rid of the knock sensor fault code and misfires.. can't stand it!

jeronberna

Here's a pic of my ECU, and some close ups of the caps.

I understand that not all bad caps are completely visible or swollen/leaking. So my issue may not even be visible, but would anyone here know how to check a Cap while it is still mounted on the board? can i use a multimeter? or do i NEED a ESR? thanks in advance

hopefully @Yamae or @LScowboyLS could chime in :3







THANKS!

Yamae

How can you judge them by eyes? Things are far more complicated than you think. You have to measure the ESR or the ripple voltage for the judgment. Or replace them unconditionally since they contain infamous fluid QAS.

jeronberna

Sorry i may have misworded that, but my question was is there a way to check ESR with a normal fluke 88V? i ordered most of the capacitors, but i cannot find any of the 2 types of 10u capacitors in the list. all of them have 16-22 week lead times, so i'm hoping to atleast just test the 10u's and replace the remaining capacitors that do come in.

I am watching youtube currently, and it seems like most people are using ESR meter to test the capacitors on-board, but is there a way to test with a regular multimeter (fluke 88 V) while the 10u is still on board?

Thanks !!

YODAONE

Digi-Key offers technical support who can direct you to an alternate equal or better Japanese branded low ESR capacitor.part number.

FloridaCam

jeronberna, Did you not drive your car for quite sometimes or let the battery die recently?

jeronberna

@FloridaCam yeah, it was sitting for about 2 years prior :/ any thoughts?

FloridaCam

It happened to me a few months ago when I left it not running for 3-4 months. It started up fine but started misfire and smoke came out like crazy when the engine got warm up. The smoke was so thick that I could leave it running when engine got to around 160+ F degree with fear that neighbors would complain or call fire fighters
But your case is different, I got misfire codes from P0300 to P0308... (not P0325 and P0330 like yours). All fingers point to the ECM in your case.

jeronberna

@FloridaCam Did you replace your caps?

I just replaced my caps, but still getting some misfires, haven't come across the knock sensors yet but gonna check after i drive around

@Yamae i just replaced the caps, but i do have that broken ceramic capacitor, could that still be causing my misfires in cylinders 3/4 and 7/8?

Having a hard time trying to diagnose this thing... Do you have any suggestions on what i could check to fix this? I dont think 3/4 7/8 share the same coil... if i remember correctly, but i could be wrong

FloridaCam

Yes, I did replace the capacitors a few years ago. The misfire happened few months ago so I didn't replace the capacitors for that. I don't remember what fixed it, but I found a bad fuel pump relay. I poured a bottle of Heet gas treament hoping to treat water in fuel tank. I cleaned the Air Idle Control valve, EGR Valve and MAF. I replaced fuel filter but it was a waste of time since fuel pressure was good.