Hello everybody, I want to start off by saying that this is my first post and I'm not a Lexus expert by any means. So I'll apologize in advance if I come off a bit ignorant.

I own a 1999 Lexus ls400 with the VVTI 1uz (I'm sure you knew that), and it has approximately 380,XXX miles on the clock. I inherited the car in 2018 and drove it for about a year and a half. Near the end of its time as a daily-driver it began running poorly, and I was experiencing transmission problems where it would shift 1-3-5 skipping 2nd and 4th. At the time I also had a plethora of engine codes such as random misfires, camshaft position sensor, crankshaft position sensor, etc.. I was quoted quite a bit more funds than I had available at the time, so I ended up parking it. Every 6 months or so I would start it, move it around a bit maybe a mile down the road and back and park it. Fast forward to last week I decided I wanted to start dumping some money into it, and when I first tried to start it I was experiencing crank-no start condition.

I tried jumping circuit open relay and fuel pump relay to no avail, and ended up finding that the fuse EFI #1 was blown causing security light (immobilizer) to stay on with key turned on. After rectifying that I had power to the fuel pump, but the pump still did not activate so I decided to replace it. After replacing the fuel pump I also replaced the Circuit open relay, EFI relay, and fuel pump relay just to be thorough prior to changing pump. I can now hear it engage and the car will start after only a few cranks, run for approximately 1.5-2 seconds and shut off almost as if fuel/spark is immediately cut. As per recommendations from another enthusiast I ran 12v from battery to pump and could hear it engage and stay running. I turned the car over and experienced the same condition. I removed the wire from the battery positive and wrapped it around a test light, turned ignition to on - no power, then while cranking it has power, for the ~2 seconds it runs, and for approximately 3 seconds after it dies.

When I was pulling intake off to spray starting fluid into throttle body I broke some hoses on the "square" part that runs off the side (silencer/resonater?). That and the piping going from throttle body to MAF section is still removed. Not sure if that could cause vacuum issues or something along those lines.

Current codes via my dollar store OBDII sensor are P0763 (Shift Solenoid C Electrical) & P0120 (Throttle / Pedal Position Sensor / Switch A Circuit). I have not gotten any codes for camshaft/crankshaft position sensor or random misfire (yet) as I assume the car just hasn't ran long enough to trigger them. It is my understanding that the car could be going into inhibiting mode. I tested the MAF just by unplugging it and trying to start car. There was no difference in symptoms but it did throw the code for MAF right away. As for camshaft & crankshaft position sensor, I just don't know how to test them and I don't want to shotgun parts at it (at least not at the moment). Also, how do I test ignitors/where are they located? Last bit of information I can think of is that the timing belt was never changed while I owned it, and I have no idea when it was changed previously because the tag under hood says 92k miles. Hard to believe it hasn't been changed in almost 300k.


I'm open to try any troubleshooting methods, and let me know if there is any additional information I may have left out. Thanks in advance

 

Have you seen this thread?
https://www.clublexus.com/forums/ls-...capacitor.html

 

Yes.. I have seen that thread. I've been reading tons of different threads over the last week or so which helped me to get where I'm at currently, admittedly not far. It's definitely something that I'm considering looking into at some point, but I'd like to check off some of the easier boxes first. I personally don't have any experience soldering capacitors, so I'd probably look for a shop in that case. On another forum someone ran me through steps for "bypassing" fuel system ECU, but I couldn't seem to find it in the locations they suggested.

One question I have about it is if instead of fixing my ECU, what kind of baggage comes with purchasing a new stock ECU or an aftermarket one? Is there any benefits to doing that over just changing the capacitors?

Also, in that post it mentions that visually inspecting the capacitors is not enough because they can look good and still malfunction. Would taking it apart to look even be worth the time at that point or should I just order the capacitors and call up a shop right away if I go with that option.

 

You need to eliminate bad capacitors as a cause or you're potentially throwing parts at the car forever and will never get it fixed, open up the ECU and have a look. Aftermarket ECU is a whole different thing you don't need to go down that road. New factory ECU is generally very expensive.

 

Fair enough, I suppose ECU could cause tainted test results when troubleshooting other things.. Do you know where exactly I can locate the ECU on my car?

 

Behind glove box.

 

Thank you, I will look into it and check back later.