mrrbearxd

I have a 1994 ls400, and it seems to have no power when I gas.
When i put it into reverse, it reverse no problem. no hesitation no sign of any problem.
When it put it into drive, idle is fine, car seems fine, but when I give it some gas the car SLOWLY speeds up. When im on park or neutral idle is fine, i gave it gas it RPM goes up no problem.
Only in drive position, it gives me problem. no power. It does not spud or misfire or anything. What do you think the problem may be? any suggestions or opinion would be a great help.

LScowboyLS

first step is get car quite hot, such as 30 minutes of driving, then park on a very level surface, cycle through each gear in succession ending up back in PARK, then check transmission fluid with car still running and see if it is at HOT mark on dipstick

mrrbearxd

Tranny fluid is normal, its where its suppose to be, any other idea? can a clogged cat cause it to have this issue?

LScowboyLS

it could, but LS400 cats don't typically clog, they are actually extremely well made and I would hang on to them for dear life!

if you want to be sure, you need this tool plugged into the pre-cat O2 socket

LScowboyLS

also keep in mind that your particular year model has a very high incidence of failing ECU caps - and the ECU is critical for both running right and transmission acting right! (and even A/C)

have you dumped the diagnostic codes on the car as shown here?

deanshark

You say it's a 94 but your other thread, (91 dash lights) and your profile both say 91. just want to clear that up b/c different years have different problems.
I don't think it's tranny related. Other then it not skipping it sounds like a coil or cam sensor problem. You say when you give it gas it starts slow but will increase as you go further, you wouldn't notice that in reverse which makes it feel normal. Check for engine, and tranny, codes and let us know what codes come up. That will make it soooo much easier to diagnose.

THXDOC

Make sure you are getting spark from both of your ignition coils. Just because it seems ok in reverse doesn't mean much, that'[ the lowest ratio gear and nobody goes that fast in "R". I had this problem, and replacing one bad coil which feeds four of your eight cylinders was the ticket.

mrrbearxd

its because i have a 91 and 94 ls400, this, in this case im talking about 1994 ls400

deanshark

Ok, just making sure. Nice to be loyal to Lexus.

on2u

Hi I have the same problem, the car is really slow when accelerating in gear, and it sounds like the car is pinging as well.

Then last week the car suddenly did not want to start, or it would drive for 20min and then stop so I decided to take out the ecu after finding the topic in this forum

I have found 2 capacitors leaking, so now in the process of getting this sorted.

Will let you know if there is any difference.

LScowboyLS

If you have 2 capacitors leaking, I can GUARANTEE there will be a HUGE difference if you do the repair correctly and use the correct capacitors!

The are NO optional caps in our ECU's, even 1 cap leaking and the car will run bad and often have other issues as well!!

on2u

Replaced all 8 capacitors!

Sympton still there

Car still dies out.
Engine check light still does not light up when all other lights are on the dash

ECU itself probably fried

LScowboyLS

did you use the exact capacitors I listed in the CURRENTLY RECOMMENDED CAPACITORS section of my ECU capacitors tutorial? - which brands and series did you buy, and where did you buy them? - these two factors are critical for the repair to be successful - most all caps, even though the correct value, are not the correct rare high temperature, low-ESR, high ripple rejection, long life premium Japanese caps - and even when you do find the correct rare type, they tend to be counterfeit unless purchased from the authorized distributor - which is difficult in Australia - either you can order from the USA distributors I linked to, or another option would be to contact Mouser (Hong Kong) +852 3756-4700 - they are authorized for 3 of the 4 acceptable brands (they do not have Rubycon)

on2u

Yes, I went with your suggestion.

I ordered from Mouser, and all arrived within 5 working days to Sydney Aust.

I was Impressed with how quick they were.

My mechanic, suspects the ECU is fried because the engine check light does not show up when the key is on start when all the dash light would show up. This was the same symptom before the change of the capacitors as well.

He thought replacing the capacitors would of solved every issue but it hadn't.


Below is what I ordered and I followed your links from the ECU Capacitor thread, and was very helpful. Thanks again for the ECU capacitor thread.

661-EKZM500E101MHB5D
EKZM500ELL101MHB5D
50Volts 100uF


667-EEU-FR1H221
EEU-FR1H221
50VDC 220uF


661-EKZE101ELL470MJC
EKZE101ELL470MJC5S
100volts 47uF


661-EKZE630ELL150ME1
EKZE630ELL150ME11D
63volts 15uF


661-EKZE500ELL100ME0
EKZE500ELL100ME07D
50volts 10uF

LScowboyLS

at this point I would probably find an ECU from a wrecking yard or ebay that is a virgin and has never been repaired and one who's caps are not yet leaking, and see if that changes the ECU light issue and other symptoms, and if it does, then replace the caps on that one.

depending on the severity of the leakage, the caustic effects of the leaking electrolyte may have ruined the ECU main lower circuit board, this is why I encourage people to go ahead and do this repair before the car exhibits any problems!