low4hunnit

I know this post has been talked about countless times. I just want a little more recent info/news/fixes.

92ls400

check engine light on intermittently code 25 only. Engine lean malfunction.
and the car has a very bad misfire almost undrivable. Heavy throttle misfires like a mffffff. Light throttle feels ok(sometimes) On idle it burps here and there.

I don’t want to keep throwing money at it. I was going to buy ignition coils and dizzy caps and rotors. But I’m not sure if it could be a sensor failing/failed. Please help. I want my baby girl healthy

replaced:
spark plugs and wires.
All coolant temp sensors.
tps sensor.
idle air control valve.
Deleted egr.

paulo57509

I would confirm that the engine is getting adequate fuel supply:

• Fuel pump providing adequate pressure/volume.
• Injectors unplugged.
• Fuel filter unplugged.
• Fuel pump pickup filter unplugged.

If the O2 sensors are reading a lean condition, the ECU should be attempting to richen the mixture by decreasing injector dwell (injector off time).

• What did the business end of the old plugs look like?

Yamae

In case the code is only 25, it simply means that the problem is only one side of the bank. I'd rather think it's a vacuum leak, clogged injectors or a failing OXL1 of bank 1. To check the leak, a smoke machine is useful to find out the exact leaking point. The OXL1 can be checked as is explained here.
If you have the code 26 too, I will add to check the fundamental fuel supply issues.

low4hunnit

the new plugs I had just put in were black. So I’m assuming the plugs fouled out from the ecu keeping the injectors open longer. I replaced with another new set or plugs. Same issue. So I decided to get new upstream o2 sensors thought one may have been failing. Still….same issue… everyone around is scared to help diag this beast😔

low4hunnit

thank you for the video.
I’ve smoked the intake before and found a leak behind the intake manifold. Assumed it was intake gaskets. Replaced them.
Smoked again and still a leak. Ended up being a leak from the vacuum line to the back of the manifold from brake booster. replaced that.
smoked again and has no leaks. This was about a year ago. And it was running fine until about 2 weeks ago.

I replaced my upstream o2 sensors and I still have the same issue…. Idk what to do

low4hunnit

Could a bad tps cause this drivability issue ?

low4hunnit

forgot to mention I have new fuel pump and filter

400fanboy

Has the ECU been repaired? Any further diagnosis is impossible until the ECU is confirmed healthy.

How to test if you don't know if it's been repaired:
https://www.clublexus.com/forums/ls-...-by-yamae.html

https://www.clublexus.com/forums/ls-...capacitor.html

Gerro

Hi All.
Had the same issue for a long time. Ended up to be a "working" coil breaking down. Idle fine and misfire on load and throttle. Take a timing light and clip on the coil wire. It needs to flash very fast, NOT SLOW AND INTERMITTENT. It causes enough spark for idle but breaks down on rev or load.

Gerro

Check your coil wire with a timing light. It must flash very quick even on idle. A coil breaking down wil flash slow and intermittently.

low4hunnit

Figured the issue out about a week ago. Passenger side ignition coil (USDM) is the culprit (Both are new now).
Threw some coils on and car misfire was gone right away.
I still have a lean malfunction code (unrelated issue). But misfire is completely gone.
Never assume something is ok just because it hasn’t completely failed.

fuel injectors are probably my issue as since I changed the failed fuel filter that was broken inside :/ 🤞🏼🤞🏼🤞🏼 Injectors on this car aren’t an enjoyable or easy job

fondu

The Injectors are a big job but everyone makes a bigger deal about removing the intake manifold then it really is. If you do the injectors make sure you replace all the rubber seals, they are rock hard now and probably allowing unmetered air in the engine.