Hello people of Club Lexus,

I understand there is a plethora of information available on these forms relating to my issues but nothing seems to fit my situation exactly and am having trouble consolidating said information.

I recently purchased a '92 LS400 with 270k km on it and noticed a few (hopefully minor) issues on the drive home. I have also taken the final, left side muffler off (I bought a V8 I want to hear one)

1. The whole car and pedals vibrate when revving the car even in park. This is supposedly due to failing engine and/or transmission mounts which should be an easy fix. Additionally the steering wheel vibrates at speeds of >80kph (the previous owner recently changed the tires but seems to be aligned alright)
2. I can't shake the feeling that the engine is noticeably tapping, it just doesn't sound right. Listening with a screwdriver seems like it is loudest in a few of the right side sparkplugs and will sometimes fluctuate.
   Placing my hand on the engine while it runs, I feel a light vibration that fluctuates every second or so
3. Running rich. Upon start-up the smell of fuel coming from the exhaust is overpowering. No liquid seems to flow out but a faint white smoke can be seen for the first 5-10 mins of running at idle. I tried running the car without the MAF plugged in but the engine began revving up and down so hopefully the MAF is working.
4. Sort of unrelated but the A/C light flashes and the fan speed fluctuates a lot when revving. Previous owner says it needs re-gassing. Hoping it's not anything else

What I've looked at:

• No CEL/ other warning lights
• Diagnostic Port (shorting E1 and TE1) the engine light blinks constantly (no stored codes) but it does show transmission code 63 (Solenoid #2 malfunction)
• ECU: The ECU has no visible signs of degradation. The previous owner said he had someone look at it but they said "it was the cleanest ECU" they've ever seen. I still decided to check myself. I've seen on this form though that a visual inspection might not cut it. Nevertheless, my car shows none of the supposed signs of bad caps.
• The previous owner recently replaced the coils and plugs with NKG and iridium plugs.
• Oil/filter was replaced recently, unsure of the fuel filter condition
• Classic issue with hood insulation getting sucked into the air intake, removed the scoop temporarily

I don't believe the O2 sensors have be replaced recently (or ever) and the MAF does show a few scratches on it and I'm not sure how sensitive it is.

Any pointers to other forums or resources like how to test certain sensors would be much appreciated, Cheers

 

ECU's cannot be inspected visually. And failures are not a "if", but a "when".

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

The motor running rough is hard to diagnose with the symptoms of the ECU floating around, along with potentially bad motor mounts.

 

I own a 1995 LS400 with 140kmiles. I live in a cold climate and have net seen any ECU issues (yet) Still runs without any issues. No engine or transmission mount issues yet Either. Not uncommon that an old car is sold after someone partially failing to do service correct. Ignition problem perhaps. A note on that is that Iridium plugs are expensive. There are Youtube videos showing how very "lookalike" fake pirated plugs look without the super tough iridium . Very difficult to spot apart from the very low prize. They can be any degree of BAD but probably works for a year or so is my guess.
1. Could be engine mount problems. Some crowbar wiggling should show if that is what you have.
2 Tapping valves could come with many miles. These engines are known for (luckily ) not needing a valve adjustment for a very long time but 270 k could probably do it. From what I remember valve tick from a few valves in rear is what typically evolve first. Ok if it is just a little, Adjusting the valves is a big job where you need to replace shims with other thicknesses you need to get hold of .
3. Could also be that your engine is misfiring on one or two cylinders. That would give fuel stink at first. A very good idea not to drive it like that. The fuel washes oil away on cylinder walls of those cylinders and CATS will produce excess heat when they have reached their working temperature after a few minutes.
Check that alla 8 are giving spark with a old plug held to ground when running, Taking out plugs a short while after a cold start could also tell. Culprit plugs would be wet and have a bit different colour,
4. A have refilled my AC three years ago. Before it gave no other symptoms than weak cooling that progressively got worse over about two years. The fan should not be related to gas content. No idea what flickering AC light might mean. Normally fan speeds are adjusted in steps by changing feed voltage to it. My guess is that the ECU handles that but it could also be another controll box? What you describe might point to ECU problem or a AC controll box issue.
5. Severe Fuel filter issues typically give problems when use of fuel is max due to starvation. Hence more than a seconds of wide open throttle at medium to high rev. Unlikley to affect what yiu expereince I think.
6. I have read somewhere that Transmission solenoids are acessable and replaceable when pan is removed. A little messy . Lets hope that ATF has been changed over the years at least once. My 1995 had the first change at about 90k Miles which is pretty late . Consensus seem to be that if no changes have been made starting at hight miles is risky because of debris that may come loose and move around. I would only risk it in that case if Trans is showing bad behaviour. VERY important to use the correct fluid.
7. Denso O2 sensors seem very long lived. I have replaced 1 of them due to cable damage only. Used Universal Denso sensor.

 

Are the spark plug wires good, inspect all of them, and look at the coils, if the coils are original to the car its something to maybe consider, make sure its firing on all 8 cylinders. So if you start it up, and you disconnect one of the spark plug wires while its running and you notice a subtle difference in the way it runs after you disconnect the wire then that likely means that cylinder is working, if you disconnect one of the spark plugs wires while its running running and you notice no subtle difference at all then you can isolate that. I would also consider a compression test on all cylinders at some point, should be approx 130 psi or higher hopefully, and no major deviations.