Car Hesitates, Has Troube Accelerating, And Idles Rough

[lexus_az]

Help! My 92 LS400 hesitates and has trouble accelerating. It starts fine and runs fine for a moment, but as it warms up or as the fuel cycles through it starts to stutter like it can't breath. It will idle rough and has even stalled a couple times. Is this a fuel issue? An air issue? An ignition/electrical issue?

Yesterday I changed my oil and air filter, added fuel cleaner and an octane booster, and replaced all my spark plugs hoping it would help, but this still happens. I read some forums online and saw that it may be due to fluid on the spark plugs causing them to misfire http://www.clublexus.com/forums/ls400/95845-1993-ls400-rough-idle-hesitant-acceleration-after-a-simple-hose-replacement.html . 2 cylinders and spark plugs may have been a bit wet/oily, should I try a wet vac to dry them out? Any suggestions? I also inadvertently ordered a part called the idle air control valve (IACV) that I mistook for the (ACV) when I had power steering problems. Will this help? Should I put it on?

Here's some background:

I recently had power steering woes that may have caused all this. My LS400 was drinking power steering fluid and it may have drowned my engine (a vacuum hose on the base of the p/s pump was sucking the p/s fluid into the intake manifold and billowing it out of the exhaust as gray smoke). I must've poured gallons of p/s fluid and quarts of rack and pinion sealant into the reservoir over the past few weeks. After plenty of trips to the shop and hiring a mobile mechanic who was unable to fix it, I finally found a really helpful thread that showed how to bypass the ACV (air control valve) to avoid this flooding problem and I no longer have power steering leaks, squeeks or problems. Here's the link: http://www.clublexus.com/forums/ls400/343856-all-in-one-power-steering-fix-s-solenoid-acv-plug-drain-flush-bleed-system-diy.html

But now I need to find out why the engine is running so rough.

Any help and suggestions are appreciated. Thanks!

[curiousB]

Assuming the car was running well before you started then the problem must be something you did in your service. Its highly unlikely that any side effects of PS fluid in the intake would magically kill the engine at the exact time you worked on it.

Things to check:

1. Double and triple check ignition wiring. Maybe you crossed a couple wires thereby losing those cylinders
   
2. Fill the tank up with fresh fuel to further dilute the magic elixirs you put down the tank. Note to self, don't use these again.
   
3. Is the problem at idle only or does the car hesitate while driving at road speeds?
   
4. If its only at idle is could be a vacuum leak. Did you leave intake hose to PS pump disconnected?
   
5. If its at all speeds my bet is ignition, crossed wiring, loose wire, or broken wire.
   
6. There is a chance your elixirs caused some sediment in the fuel filter to come unlogged and plug up an injector but I think you rule out other factors before jumping into this one.
   

[lexus_az]

Assuming the car was running well before you started then the problem must be something you did in your service. Its highly unlikely that any side effects of PS fluid in the intake would magically kill the engine at the exact time you worked on it.

Things to check:

1. Double and triple check ignition wiring. Maybe you crossed a couple wires thereby losing those cylinders
   
2. Fill the tank up with fresh fuel to further dilute the magic elixirs you put down the tank. Note to self, don't use these again.
   
3. Is the problem at idle only or does the car hesitate while driving at road speeds?
   
4. If its only at idle is could be a vacuum leak. Did you leave intake hose to PS pump disconnected?
   
5. If its at all speeds my bet is ignition, crossed wiring, loose wire, or broken wire.
   
6. There is a chance your elixirs caused some sediment in the fuel filter to come unlogged and plug up an injector but I think you rule out other factors before jumping into this one.
   

Thanks for the tip. B/c the problem started before I made any changes to the ps (was actually the last straw that made me start working on the p/s), I don't think it was something I did.

Checked the wires.

I filled the tank up with high premium gas when I added the additives--I usually try to avoid using these, but at the recommendation of others that the fuel system could use a good cleaning I went for it.

The problem is at both idle and at road speeds

thx!

[SRK]

The engine has two ignition coils, which you may have seen working around them. Check them both, one may have failed, and that's common.

[Thermactor]

Run some seafoam through the intake manifold, that might help a lot.

[JTom]

I have the same problem, 92 LS400 idles rough, it died while actually driving once, found out it's the fuel pump relay resistor. Works fine maxed out but can't find the resistor to replace it. http://www.clublexus.com/forums/maintenance/229393-ls-400-stalling-problem-solved.html