neostar43

Any help would be appreciated! 93 ls400

Currently, the main issue that I am having is the RPMS go from 650 and fluctuates down to 200-300. the fluctuation is worse when the car is in drive. It has not stalled...yet. When I first got the car in August it did not have this problem. Had other problems like a bad ecu.

The fuel filter has been changed. Spark plugs , spark plug wires, ecu, 02 sensor, changed some vacuum lines, replaced maf, iacv has been cleaned, tb has been cleaned, pvc has been changed. bg44k has been put in gas tank. transmission flush and speed sensor changed.

The car looks as though it still has original timing belt since it has cracks in it I will have that done in january. would a timing belt cause this problem? I just purchased a new fuel pump will see if that helps. What else could cause this?

my fear is having the timing belt done and the problem is still there. Money is tight until january.

neostar43

also, when i am driving car. the car power drops off then returns just like it does when parked when the idle is fluctuating.

PureDrifter

iTrader: (10)

hunt for vacuum leaks, check ISC, and make sure the timing is in spec (you can't adjust it but can check it. usually if it's off the belt jumped a tooth)

python

iTrader: (4)

no check engine light? cuz i gotta tell ya u r throwing parts at it and u should have taken it to a shop..cheaper in the long run

neostar43

no check engine light. I jumped the obd connector. no codes.

I initially took it to lexus cuz on the way from PA to VA after I bought it, I was losing power. Took it to lexus and they had to change out the ecu and a o2 sensor. I was back on the road. I then changed the other items... tires, brakes and rotors, k&n air filter, gas cap, radiator cap, et cetera. the car ran fine. then one night on the way home. it was acting wierd as if it did not know what it wanted to do. Found out the power steering resevoir was empty and making noise. It was replaced by lexus about 70k miles ago though. I refilled it with lucas fluid and it drove normally. then it started to give me the current issues.

So, I changed the spark plug and wires, still the same problems, changed some loose vacuum lines. same problem. then tonight I ran about 2/3 of seafoam thru the intake. Smoked like a chimney! also, changed out the coolant sensor.

To my amazement, seafoam and the sensor cured the problem(for now). I have more power and the erratic rpms are gone. it does not run as smooth as it should in my estimation however. and also, the car squeaks and lurches when i put it in drive. I may need some motor mounts. I am going to drive it for the next few days to see if the problem returns. If it does I am going to change the fuel pump and in january get the
90k miles service done by lexus. this car is as tough as 300zx. to work on and figure out.

thanks for the current responses. more ideas would be appreciated.

also, the norfolk police dept on novemeber 18th is having an auction for abandoned vehicles. they have a 90 lexus ls400 whose timing belt was changed by lexus at 87k miles according to lexus.com. If anyone is interested, you probably could get it for under $1000. should be a good parts car if nothing else. go to: http://www.norfolk.gov/PublicWorks/auction_list.asp

neostar43

i have fixed the problem

read below post for solution

https://www.clublexus.com/forums/ls400/536813-75.html

RA40

iTrader: (6)

What a hunt...glad that was resolved.