(1991 ls400) Car was driving fine on all 8 for the longest time, ironically drove 35 minutes to a junkyard, and the second I pulled into the parking lot I felt a lot of vibration.
when I came to a stop the car is clearly barley running, but it’s in and out. In park it’ll just run rough and vibrate real hard, when I put it into drive it’ll run almost rougher and sputter like it wants to go itself, like another cylinder kicks in for a second then dies off again.
I was also noticing a not too pleasant noise coming from under the vehicle almost like a metal noise. (The car never dies completely, it won’t stall out, granted I havnt sat there and just let her run for an extended period of time like this. But from each time it’s been running since it hadn’t stalled.)

No new oil leaks or anything, and the car still starts up fine it just runs horribly. Do y’all have any pointers for me? Is this a symptom of jumped timing? I am leaking at the cam and crank seals, and probably the oil pump too.

I know it’s not the ignition coils, and it’s not the plug wires as those are all newer.

also has no new check engine codes. It’s had a code 71 for the longest time, I checked codes this morning and that is still the only code I am reading.

 

Have you inspected the ECU?
https://www.clublexus.com/forums/ls-...capacitor.html

 

I did a few months aho and everything was fine with it. I’ll take another glance at it when I get back, if it nothing is obvious I’ll do some extended testing

 

An ECU cannot be visually inspected. Symptoms can exist from an ECU which is not visibly leaking (yet).

https://www.clublexus.com/forums/ls-...-by-yamae.html

 

Thank you so much for sharing the link.


 

I was doing some more testing. The car will only start with the lower ignition coil plugged in.

went to the store and got a new ignition coil for the top, and it still will only run with the lower one plugged in, so I swapped the wires on them and still only the lower is working.

maybe distributor? I’m not sure how these usually fail, but at this point I think we can cross out it being the ECU, but it’s giving me very similar symptoms to when my ignition coil went out the first time.

 

Also I went though and cleaned everything in the EGR system, and yall it was so gunked up with carbon build up the passage ways were completely clogged up. I cleaned everything up and that check engine light went away immidately.

And im not getting any cel for my current issue

 

but would this ECU test still be accurate with the car running as rough as it is?

 

I'm not an electrical engineer - but the voltages aren't related to the speed of the engine or anything like that. So I think it should.

I'm not sure if you can test in accessory mode, or, if the engine needs to be running. Maybe the thread has that info.