Good morning. After a cam seal change (where I broke and replaced the cam) my 2000 LS400 was running good. Super smooth and no dash lights at all. Made several short trips including some gentle, high rpm test trips.

On a 20 minute local drive the dash lights came on and I barely made it home. Flashing CEL, 'Check VSC', no individual codes stored. Pulling coil wires on the driver side makes no difference in the idle. Pulling passenger side does impact the idle. When starting it now, it has an irregular spin before firing and running very rough.

Recapped ECU with the good capacitors about 70k miles ago.
Double checked timing belt marks at cams and crank.
Intake and exhaust cams I previously removed are single-dot to single-dot.
There is an alternating signal at the #1 fuel injector.
There is spark at #1 spark plug.
Proper resistance in the cam sensor and crank sensor on the front of the engine.
The cam sensor in the middle of the head has a similar resistance although I can't find a spec for what exactly it should be.
Visually checked the replacement cam for a break.
Checked resistance of the cam and crank sensor wiring all the way from the connectors back to the ECU.

I hope someone has some experience that can help. This car is a fabulous car. I've owned it for almost 90k miles (150k to nearly 240k). Attached is a fun picture of my daughter doing some driving training in it.




Rich

 

Well as you know the flashing check engine light is related to misfires and is warming you that you can damage the engine if you drive it in it's present condition. That cam seal job is a pretty intense DIY and I would hate for you to have to open her back up. With no codes the only thing I can think of is for you or someone else to use a timing light to make SURE that the timing is dead on. Also check for vacuum leaks since that would not throw a code all the time.

 

I would check the ECU again at this point.

 

I appreciate the replies!

I have a friend's 1999 LS400 I'm doing a head gasket on. So I'll swap that 1999 ECU into my 2000 and see what happens.

Also plan on checking for vacuum leaks and maybe a compression check.

It's sad to see these two cars broken down. They are both awesome driving vehicles and have been very reliable.

 

About swapping ECUs around, I thought that they were coded to the key in the 97-up models. So if you are borrowing your friends ECU, maybe ask for his key as well and hold it near the steering column when you go to turn the car on. Not sure if this even applies to the car but I’ve heard of it being done before.

 

Thanks again everyone. As Sha4000 mentioned, it's a big job to tear it down again. But I did. I disassembled until I found something wrong.

I found a loose bolt! The bolt that holds the VVTi actuator to the end of the cam was loose! The pin that orients it was completely sheared off.

Reassembling with a new cam today! And I added some thread locker this time :-).

 

What a story🤪
Good job finding the root cause!

 

Sometimes that's the easiest thing to do. It's frustrating when you waste time looking at other things and look up and you wasted a day or two before you finally just do what you know you should have done in the first place. I've been there a couple of times.