So as the title says what I haev on my hands is a 92 LS400. When I say it doesn't have power I mean when you drive it really. Doesn't seem to want to go like a V8 of it's size should. Doesn't sound like it's missing anything. Almost sounds like a LITE rough idle. Like if someone's talking to you, you can't hear it. You really have to listen hard to hear the roughness. I'm sorry I'm not too sure how to really describe it. If anyone has any ideas of what I could look for I would greatly appreciate it!!!!! Thanks!!!!

 

when was the last time u did spark plug, spark plug wire, distributor cap and rotor change??

 

yea, tune it up, and be prepared as these cars are HEAVY and arent that fast...

 

I have the same problem on my 91 ls too. On idle, it sounds like it misses a cylinder now and then. I already changed wires and sparks but that didnt make a difference so now ive ordered rotors and caps.

Will post when i replace.

 

how long have you had her? was she better in the past?

 

Keep it simple -- Air, Fuel, Spark. Three basics. Make sure all systems are clean and operating properly and your power should be there.

If it isn't,.. then you either have an electrical problem (which would include computer) , or ... engine assembly troubles. (Compression loss and other such devestating blows).

I'd rule in the favor of the former, Air,Spark, Fuel arena.. Your post screams tune up -- But don't just stop at the plugs.

Check fluids, top them/flush what needs it. Change PCV, check ECV -- plugs, wires, rotors, (test ignition with meter) -- Change fuel filter,.. make sure pressure is good,.. no leaks in injectors, and on and on.

An engine is an engine,.. eventually you will figure it out.. that is half the fun.


PD is right, these aren't Mustangs or Corvettes.. But they are 260-300hp V8's.. They are only as slow as what one is used to. Most people would call them 'powerful'.. not quick.

That is how I classifiy it -- Any car that will hit 155-160mph, go 0-60 reasonably quick, and pulls away at any speed with ease is powerful.

 

i would say injector misfire..........put some reline fuel system cleaner in it and see what happens, as for the first post it could be a plugged up cat.......just suggestions here

 

I couldnt agree more. all sooo true

 

May not be that simple. I am experiencing similar problems, and I recommend you read my entire thread with the least of everything I've changed so far over the course of two years, and still no cigar.

https://www.clublexus.com/forums/sho...d.php?t=238892

In the end I found some information that our cars appear to have some inherent computer problems, and the proper way to fix it would be to replace the computer (ECU, ECM, PCM) with a brand new unit, which costs around $2,000 from the dealer. A work around could be using a "Piggyback computer" but I dont know how well it will work.

In any case, before you do anything and start replacing parts, take your car to a diagnostics shop and have the run a full scan on it. If they pinpoint the problem, even if its expensive to repair, at least you wont have to do the guesswork by replacing wrong parts from "good to new". I know I've learned the hard way.

 

Good tip Och -- But I included the 'computer' in my simple explanation. So it was covered.

Getting a code scan should be an obvious step with a poorly running vehicle.. It goes unsaid, I thought.

Although, I'm a little .. mehhh on the 'don't replace parts' theory -- If the plugs/wires and such are due anyway -- Go ahead and do them. You will end up having to do it anyway, and it will run a little more efficient with the new equipment.

IE:

NGK plugs, Wires, Fuel filter, air filter, PCV, clean throttle body.. (Inspect MAF, but don't clean it) -- Check TPS,.. pull codes, if any. If no CEL is on, there may not be a code even with the rough engine. Check fuel pressure on the line.. Not hard to do. Make sure no clogs in the airflow from our 'air ducting' to the intake manifold. -- Check MAF readings with a multimeter .. ensure it is giving proper values... that alone can cause a rough ride. (this is digging into electronics, but is a few minute job and free) -- Just do the cheap / free stuff first.. then move into the next 'cheapest' and so on. -- (I just bet you don't have a CEL or code that is going to point you right into the problem)

Don't forget O2 sensors and EGR system.. though you can test them.

 

Very good tips, and I personally don't regret replacing most of the parts that I've replaced - most of them would be due to replace at some point anyway. Except perhaps for the MAF, it was a big hit on my wallet.

But sometimes people are just looking to repair the specific problem that causes the issue in question, this is why I suggested to have the car diagnosed to pinpoint that problem.

 

check coil packs.