718murdoc

First let me start by saying I have no gripes with the sc400 but mine is really starting to annoy me.The problem started back at the beginning of 2009, my car had a very rough idle. The idle would jump between 800 RPMs and 2000 RPMs. I brought my car to a trusted mechanic to have the problem sorted.I wound up doing a tune up. They figured it was bad spark plugs and wires. The problem was still there. After 2 more attempts to solve the problem I got frustrated and told the owner to just give me the car. As of now the car is parked until I can save the funds to fix the car at a lexus dealer like I should have done from the beginning. The tech did tell me it looks like the engine harness is bad and as a result of this the power is not being distributed to the engine correctly. If this is true then I know repairs at the dealer are going to be expensive. Does anyone here on CL have a used complete engine harness to sell? If so please leave contact info. Also if anyone knows a solution for this problem you are welcome to chime in.

lexdud

OP, do a forum search for this problem. It has been reported a few times. Sounds like a dirty/bad IACV and/or ECU. If that is the problem the dealership will charge you $700 and $1,500 each and then labor on top of that.

718murdoc

Actually I didn't mention it before but I did clean the IACV with carb cleaner which was friends idea and still nothing. I guess the next thing would be to check the computer.

SCLexxxy

I'll sell ya an ECU 1UZ baby

5sp_jzz30

iTrader: (2)

cleaning the IAC doesnt usually do much. the stepper motor goes bad. you need to get a good working unit or take yours completely apart and theoural clean it.

i have never seen an ecu issue causing this.

willhickey

iTrader: (1)

i think its a vacuum leak . , i would do a smoke test and see if you see anything after all its a 10 plus year old car and rubber hoses arent meant to last forever just ask your powersteering hose!!!!

718murdoc

That is so F***ING true, when I first got this car way back in 07 the power steering system decided to go on strike for it's new management.I wound up changing...
the rack,
the tie rods,
and all related hoses.

718murdoc

Is there any companies that you know of that will rebuild the unit???

718murdoc

Thank you, but i'd prefer an IACV if you have one to sell.

BostonSC4

iTrader: (2)

do you have any Check engine lights? mine did the same thing and the mechanics did the same thing...they throw parts and OUR money at it attempting to hopefully fix the problem then reap the benefits....its horse *****. mine turned out to be the mass airflow sensor. try this, go out and unclip your mass airflow sensor, its on the passenger side on the air intake, just one clip, unclip that. start the car up, you will have 2 check engine lights on but report back what happens...if the car runs beautiful...then thats your culprit.

718murdoc

I've changed the MAF at the shop, they told me that would remedy the problem but it didn't. And yes,there is a check engine light on.The weirdest thing is that the mechanic told me that when they first tried to run a diagnostic on the car the port was not where it should be,the port was actually gone!!! They said that all the wires underneath the dash were chopped and spliced, it looked as though the original owner tried to either run an aftermarket stereo setup or alarm. I could not really disagree with the guy at the shop because when I first bought the car one of the issues I had with the owner was the fact that the radio didn't work and thats one of the reasons I was able to talk the asking price down.
I didn't care about the radio because all my $$ was going towards power add ons and a paint job.If I knew about these problems I would have walked away from the car.I'm not going to cry over spilt milk.
My plan for the new year is to either solve the issue or swap out the engine for a 97 engine and harness.
Wish me luck.

lexsc4oo

iTrader: (1)

Not sure if anyone else has tried this but mine started to do this, when idling would cycle from 750-2000. i loosened the tps up and turned it about a 1/8th-1/4inch turn to the right and for some weird A** reason problem solved idk how but it did.

HeisLegend

This sounds like something my 14 year old brother would say.

I may not be able to pin point what it is that you're experiencing but this suggestion, though always possible, I think, is a bit far fetched.

5sp_jzz30

iTrader: (2)

your stereo system or any type of alarm will not/should not have anything to do with your diagnostics port.

the wiring for an alarm is all the kick panel and the ignition harness on the steering column.

the radio wiring has nothing to do with that port either. nowhere near it.

sounds like your mechanic is a ******-tard. get someone that can actually diagnose cars.

im 95% SURE another way to run a diagnostics test is to use the port in the engine bay. you can grab a paper clip and jump terminals and get the same test mode as if you used the round plug under the steering wheel.

do a search on how to put the car into diagnostics mode.

most common problems are vacuum leaks, bad IACV, distributor issues.

ecus dont go bad. at least i havent seen ANY on any lexus ever, even when working at a toyota/lexus specialty repair shop for years.

ignititon coils are common but its definitely not your issue.

i say get a different mechanic. its hard to diagnose cars online lol

good luck mate

718murdoc

Thank you so much for your insight.I'm in the process of getting my car diagnosed at another shop,(fingers crossed) I hope they find and fix the problem to put an end end to this ongoing nightmare.