1999 LS400 electrical ordeal

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JBrady

Active Member
Messages
1,776
Location
Houston Texas
Recently had a bit of "fun" with the 400. Thought I would post some details as it may help another member or two.

Replaced the factory battery in 2005 with an Autozone. Not best or first choice but it was available. Since then it has "eaten" a battery every year or so. Voltage always checked out and always had a warranty so just R/R with another when needed.

Couple weeks ago the same old slow to start symptom of "needs a battery" reared it head. Went to the closest Autozone and decided to check voltage first... 18 volts
Upgraded to the best battery they had and had them check my charging system and viola 14.4 volts. Good to go. Still, that voltage reading prior to replacing was a concern.

Few days later, slow to start drove to a customers and then back. Checked voltage... 20 VOLTS...

Well, ok, 200k miles... time for an alternator... well, voltage regulator probably but since it is internal might as well replace. Sewell Lexus lists an alternator at $442 and the regulator at $187. Advance Auto had one for $200. Manager "convinced" me they had very good luck with this brand even though it is made in China. Convenience and time had me go with this choice, with tax and $24 core charge out the door for apx $250. Thing is brand new and quality "looks" spot on.

Now, I could pay someone to change but like others have realized you never know what has really been done and how unless you do it yourself. August in Houston means high 90s and high humidity so I decided to wait until evening time. Well, started at 11pm and started it up at 4am This job is a definite PITA especially at night on jackstands. The REAL head shaker was that the voltage reading was now 22 VOLTS

I started thinking about this and thought... is it possible that my meter is jacked?
After sleeping... drove to Advanced, popped hood, checked voltage with my meter, 24 VOLTS...
Checked with their meter... 14.4 volts... "you have got to be kidding me... right?" Lesson learned.
So, my 200k alternator is now my "spare" just in case "China" goes on strike.

End of story? Nope.

Week later starts running rough... like down a cylinder rough.
First thought was a coil had quit but forum consensus as an oil control valve for the VVTi.
Pulled codes and OCV along with missfires and ignitor on cyl 6.
Decided to replace both OCV's, took less than 30 minutes, started and ran like silk
Drove to the store on the way to the golf course and on restart was back to ROUGH

Figured it must be the coil on #6. But... NOBODY had one except Sewell and that would not ship till the next week (this being on a Friday).
Let it sit over the weekend.
Then, started thinking, had to pull the resonator box off the passenger bank valve cover every time I did this work. MAYBE I had a loose connection on #6???
Sure enough, VERY slightly loose. Slight push down, restarted... SMOOOOTH!!!
Been great every since.
Apparently after enough misfires the ECU turns the cylinder off completely. Or that is how it ran anyway.

Hope this helps someone.
 
John, what kind of meter were you using that produced readings like that, and how old was it?!

I have a similar story with some jumper leads - 2.5 days worth of troubleshooting for naught because of a dodgy jumper lead that was somewhere between 40-50 years old. Bought it when I was a kid & it still worked fine (or so I thought).
 
It is relatively new, less than 5 years old, not at hand as it got tossed in a box but most likely made in China. Had an ancient one before that, was my dad's before that and he likely acquired it used... probably well over 50 years old... the leads finally fell apart.
 


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