Danny365N

iTrader: (1)

If anybody can help me with this I'd appreciate it very much as it's left many experienced people stumped including myself. No codes are coming up. My dad used to own a shop so I've tested it with his autoboss and autel scanners.

Alright after taking the '91 Lexus LS400 out of retirement as it sat in the garage for a year it gave me problems smelling like fuel and really lacking power when you give it throttle. I let it run for a while after putting new gas, octane boost & cleaner. I drove it on a tank and out of about 10 gallons I got maybe 90 miles. Was told injectors are damaged and spraying fuel so I got my own and got them replaced. Also running without cats due to heating up and didn't want them damaged. It ran alright for a day but then started up again causing me to believe it wasn't the injectors which are not cheap... Yesterday I got the idea that it may have been the throttle position sensor due to I'm putting the throttle all the way and it's barely going to 2500-3k rpm which I figured would be the cause of the excess fuel also . I replaced the TPS and it changed nothing. Could it be a fuel pressure regulator or something else? Any ideas and similar experiences are welcome as this has confused my dad & me.

Danny365N

iTrader: (1)

Replacing ECU tomorrow, hoping it'll fix the problem.

LScowboyLS

make sure the ECU has had its capacitors replaced with the correct type of Japanese low-ESR capacitors as detailed in post#1 of my leaking ECU capacitors thread

Yamae

Looks like you are wasting money and time changing parts next to next.

Most of failed ECU can be checked just measuring the ripple at sensors since many of them are capacitor related which causes too much ripples at the regulated low voltage DC lines in the ECU. Sensors except some are supplied the DC from there and you can check the ripple at one of those sensor lines such as a coolant temp sensor lines.

LScowboyLS

yamae - I think you and I are almost the only CL members who know how to check ripple on a sensor line, can you provide a quick tutorial for everyone?

Danny365N

iTrader: (1)

Thanks LSCowboyLS I just saw your guide about that a while ago which is when I started to think about the ECU as a whole. My capacitors weren't switched out and I'm going to swap my ECU to a buddy whom has a business rebuilding computers for Japanese cars. I discussed the issue with him too and told him about the new capacitors and he assured me his rebuilt ECU has the updated capacitors. Comes with a year warranty also and the charge is next to nothing. Personally that's much better than having the chance of me messing it up.

Yes Yamae it has come down to the fact that its money being thrown away, I was able to return the TPS. Somebody else insisted injectors were the issue and it made sense at the time. Luckily my dad has an account with IMC so I was able to get them at about half price compared to the dealer. Cringed when I saw those prices. I'm not really bothered by putting money into it. I love this car and look forward to driving it again. I actually saved this car years ago from somebody who didn't care for it/didn't have money to properly maintain it and I personally did over 3500$ in repairs just to get the car to that "good as new" feeling. It ran really great until I garaged it for so long :[

Hoping the ECU will do the trick tomorrow. I'll let you know and appreciate both of your help. I've been looking more through the Lexus community and wow. It gets better than just the cars, seems like a good group of people on here. Thanks.

gsmoot1

I have a 1991 lexus ls400 having the same and more problems including surging,power loss, tachometer ,gas needle not working properly or not working pulled the ecu no burnt capicitors or resistors board looks good could this be fuel pump or wiring harness ?