GenericUse

I'm back yet again. My LS400 still refuses to run properly. It will occasionally lose power, and doesn't really have as much as it did when I bought it to begin with. When it loses power, it also shifts at strange points (though that might just be me mashing the gas to get it up a hill). I also noticed it was losing connection to the scan tool pretty frequently but I'm not sure if that's due to a loose adapter on the scan tool's part or the ECU. I am suspicious of it, though.

Here's a list of the things I can remember checking;

-Replaced ECU. Checked caps, all appear to be Nichicon caps of the correct type.
-Checked TPS. Operating normally.
-Checked coils. Both fine.
-New fuel pump.
-New fuel filter.
-New fuel pressure damper.
-Fuel pressure regulator works well.
-Replaced distributor caps/rotors.
-Replaced spark plugs and spark plug wires.
-Replaced front O2/AFR sensors.
-Checked IACV, working normally.
-Checked EGR valve, was leaking. Blocked EGR valve with solid gasket.
-Replaced fuel injectors with 4 new/4 rebuilt units.
-Checked trunk wiring. All fine, re-wrapped with new electrical tape.
-Checked cam sensors. Both working properly.
-Crank sensor is reading RPM correctly.
-Knock sensors are working.
-Compression tests within 10% of factory on every cylinder.
-Power balance test says all cylinders within 25rpm of each other at 2200rpm.
-PCV works.
-Alternator is charging at proper voltage/amperage.
-Timing belt has not skipped teeth
-No intake vacuum leaks.
-No exhaust leaks.
-Not overheating.

Probably some other stuff too. The new ECU fixed most of my previous issues but the problems I mentioned above still remain. I'll add things to this list as I remember them or people remind me of them.

Also tested:
-MAF sensor and IAT sensor.
-The ECU is now a known good, for sure.
-ECU grounds are good.

Yamae

Are ECU capacitors Nichicon P series?
If so, you have to check the ESR of them or simply change them all. Aged P series can't absorb ripples due to the high ESR.

GenericUse

They've been replaced, the ECU was a rebuilt unit. I assume the method for checking ESR is over on the main ECU thread?

YODAONE

MAF Sensor?

GenericUse

Oh, yep, forgot that one. We tested the MAF (or AFM, really) and the IAT sensor too. Both fine.

400fanboy

-Checked EGR valve, was leaking. Blocked EGR valve with solid gasket.

This one is weird to me. Did you stop the leak? Or did you block the EGR system entirely?

The ECU may be "dealing" with it in weird ways if it's blocked from operating normally.

Yamae

You mean those Nichicon capacitors are EP or HW series?

GenericUse

No idea. They say 'Nichicon' on them and most of them are black, are there any identifying marks I should be looking for?

GenericUse

Yes!

I just replaced the metal gasket at the valve with a solid exhaust gasket, figured that was the best way to do it. Not like I can buy a new valve.

Yamae

Look for the side of the capacitor and you can find the series name like this.

GenericUse

here's what my ECU has:

Yamae

So you still use the original infamous P series. I must say that your ECU is not yet re-capped using our recommended ones. P series were discontinued more than 20 years ago and not available any more. Also as far as I know, P series were sold to ECU making companies only. Replace them before you waist your precious time and you will be happy.

GenericUse

Really strange, as they all look absolutely fine. None are leaking. I was wondering how the 'rebuilder' managed to solder so cleanly, turns out they just didn't rebuild the thing. At the very least this one IS rebuildable, as opposed to my original one where most of the caps melted >2mm wide holes in the board.

Yamae

How can you check electronics components only seeing them by human eyes? In case of capacitors, you need to use an ESR meter at least.

GenericUse

as in "they aren't actively eroding the PCB directly in front of my eyes where I can see it." Physically, they look fine. That doesn't mean anything, though. I just thought it was strange given the usually violent deaths of these capacitors.

Is there anywhere reputable I can buy an actually rebuilt unit from? I use the car seven days a week, so I can't send the newer ECU in for repair and the car is completely undrivable with the old ECU.