Allen9001

Alright I have a 94 ls 400, it has started running rough at idle, if I accelerate over 2000 rpms it loses all power and sounds like its sucking air, it stutters when accelerating slowly but smooths out once I get up In speed, I can put the car in neutral of park and it will rev up above 4000 rpms with no stutter at all. So far I have replaced the Ecu and mass air flow sensor, also searched for vacuum leaks with carb cleaner and the cigar trick as well as replaced the fuel filter. Does anyone have any suggestions or similar issues?

Allen9001

Also to add it doesn't start running rough until after it warms up.

RA40

iTrader: (6)

Welcome to Club Lexus.

Some threads to get you going:
https://www.clublexus.com/forums/ls4...capacitor.html

Although yours in a '94, many similarities exist between the 95+:
https://www.clublexus.com/forums/ls4...questions.html

Tutorials:
http://www.lexls.com/

Allen9001

Ty ill be sure to look through these

LScowboyLS

have you scanned the car for codes?

Allen9001

No as the check engine light will only come on when I accelerate hard and it loses power and drops rpms, after I let off the gas pedal and gradually accelerate the check engine light turns off. Never thought about it but would those error codes store even though the light turned off?

LScowboyLS

Yes, some error codes will definitely store even with no light on persistently, and even the absence of any stored codes after the light has come on and gone off, can be a clue in itself!

Allen9001

I'm getting error code 41 for the tps

LScowboyLS

I would check the wiring and then replace the TPS and adjust it as per the service manual procedure - ONLY use the genuine Toyota (Nippon Denso) part on the TPS - I may have a line on where you can get the real factory part for about half price, yet brand new.

Allen9001

If you do I'd love to know

LScowboyLS

not promising you, but I have ordered this item in the past, and what has shown up has been the real Denso part, but in a GM or other type box - sure beats $160 at the dealership for a high probability of getting the real Toyota part.

Allen9001

Awesome thanks, ill be sure to let you know how it goes

kayuwong

Code 41 when acceleration hard, engine hesitate a little, and if accelerate gently then thing is ok. Just had it smog check and of course it won't pass, fuel was running lean. This car has an ecu replaced a year ago from junk yard. Any idea it may be another faulty ecu here?

Yamae

You'd better not to expect a junk yard ECU. Most of them are not fine due to the aged electrolytic capacitors. Prior to use it, you definitely need to replace them using low ESR ones.

LScowboyLS

yes, you very likely have failing ECU capacitors - please use the information in the thread to fix this common issue