Need Help. 1993 LS400 absolutely refuses to run properly.
#1
Need Help. 1993 LS400 absolutely refuses to run properly.
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.
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.
Last edited by GenericUse; 04-25-21 at 12:31 AM. Reason: info
The following users liked this post:
BNastee (03-16-21)
#3
They've been replaced, the ECU was a rebuilt unit. I assume the method for checking ESR is over on the main ECU thread?
#4
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.
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.
#6
-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.
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.
Last edited by 400fanboy; 02-19-21 at 01:32 AM.
#7
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#8
#9
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.
#12
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.
The following 2 users liked this post by Yamae:
BNastee (03-16-21),
CamFerazzi (04-25-21)
#13
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.
#14
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.
The following users liked this post:
BNastee (03-16-21)
#15
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.