Rough Idle...Need Help
03-11-16, 04:52 PM
#1
Driver School Candidate
Thread Starter
Join Date: Mar 2016
Location: northcarolina
Posts: 11
Likes: 0
Received 0 Likes
on
0 Posts
Rough Idle...Need Help
I recently bought an sc300 as project! It does need love like I said its a project I bought for my daughter to work on. Right now its got a rough idle so the o2s have been changed plugs wires distributor cap & button & still runs like crap. Sounds like a Subaru if that helps! Stalls out at a stops so if anyone can think of anything please help. Thanx!
03-11-16, 05:15 PM
#2
If the ECU (capacitors) hasn't been serviced, that's the best place to start. They all need it by this point and that will eliminate a ton of guesswork.
Cleaning the IACV sounds worth a shot and is a free, relatively painless one to tackle. Maybe check the setting of the TPS, as well.
Cleaning the IACV sounds worth a shot and is a free, relatively painless one to tackle. Maybe check the setting of the TPS, as well.
03-11-16, 05:35 PM
#4
Pole Position
Join Date: May 2015
Location: CA
Posts: 208
Likes: 0
Received 0 Likes
on
0 Posts
I recently bought an sc300 as project! It does need love like I said its a project I bought for my daughter to work on. Right now its got a rough idle so the o2s have been changed plugs wires distributor cap & button & still runs like crap. Sounds like a Subaru if that helps! Stalls out at a stops so if anyone can think of anything please help. Thanx!
Dude,
What are the error codes, if any?
.
03-11-16, 05:47 PM
#6
Pole Position
Join Date: May 2015
Location: CA
Posts: 208
Likes: 0
Received 0 Likes
on
0 Posts
Dude,
It's OBD1 and has standard Toyota OBD1 error codes via the check engine light. If the check engine light is not functioning then it's either the ECU or a burned out bulb.
https://www.2carpros.com/articles/le...eval-procedure
-
Trending Topics
03-11-16, 06:11 PM
#10
Pole Position
Join Date: May 2015
Location: CA
Posts: 208
Likes: 0
Received 0 Likes
on
0 Posts
Dude,
That means it's operating properly. Time to check for error codes. If it flashes quickly and repeatedly, then that means there are no detected error codes. Here's a video of a dude wearing a nice hat checking the Toyota OBD1 error codes on his Toyota 4Runner. It's the same procedure for your Lexus.
Have fun
.
03-11-16, 07:14 PM
#12
Sometimes the ECU won't always throw a code if it's starting to go bad. Mine was tossing too much fuel at the motor and flooding it at idle once the car was warm. It only threw a code every now and then, I opened it up and one of the capacitors had leaked all over the corner of my ECU. I don't even remember what code it threw but it was for something I had just replaced which made me suspect the ECU.
There's a vendor on the forum called Tanin Electronix, they also have a website etc. They do ECU repair by replacing all of the capacitors on the ECU and cleaning the motherboard as well as they can depending on how bad the leak was. You basically just send the ECU to them and they repair it and send it back. I sent mine to them it took about a week for them to receive it, fix it and send it back.
You can open up the ECU yourself and inspect it to see if any of the capacitors have leaked. If they have it's pretty obvious as it leaves a bunch of black goop on the motherboard.
Like t2d2 said, cleaning the IACV is also a great idea, it's also possible the MAF has gotten dirty on the car. They are pretty tricky to clean properly though, however there is a DIY on the forum about how to clean them, I successfully managed to clean mine when it gave me problems 2 years ago, it just took me two tries to do it right. If you don't want to tackle that you could try and find a used one, or just bite the bullet and buy an expensive new one.
Also you said you did the Distributor cap, did you replace the distributor rotor as well? When they get old they can get really charred at the end and not transfer a complete spark, so you want to make sure you replace the rotor at the same time you replace the distributor cap.
Also is any smoke coming from the exhaust, does the exhaust smell of fuel once the engine is warm? If yes to both you could have some faulty injectors, or problems with the engine harness. I recently also had that problem as well as a myriad number of other problems with this damn car, and it was causing similar symptoms of stalling out at idle and a rough uncertain idle. I pulled the fuel rail, had the injectors flowed an serviced at an injector shop here in town and got a brand new fuel pressure regulator for the car. This is a bit rarer for the 2jz though as the injectors usually stay in pretty good shape unless the car sits around for a while, but it can still happen like it happened to me. So its something to consider.
And if its none of those things, and not the plugs, wires, or rotor cap then it may be time to douse the car in a healthy spread of e85 and set it on fire to collect the insurance money. This car drives me mad I swear.
There's a vendor on the forum called Tanin Electronix, they also have a website etc. They do ECU repair by replacing all of the capacitors on the ECU and cleaning the motherboard as well as they can depending on how bad the leak was. You basically just send the ECU to them and they repair it and send it back. I sent mine to them it took about a week for them to receive it, fix it and send it back.
You can open up the ECU yourself and inspect it to see if any of the capacitors have leaked. If they have it's pretty obvious as it leaves a bunch of black goop on the motherboard.
Like t2d2 said, cleaning the IACV is also a great idea, it's also possible the MAF has gotten dirty on the car. They are pretty tricky to clean properly though, however there is a DIY on the forum about how to clean them, I successfully managed to clean mine when it gave me problems 2 years ago, it just took me two tries to do it right. If you don't want to tackle that you could try and find a used one, or just bite the bullet and buy an expensive new one.
Also you said you did the Distributor cap, did you replace the distributor rotor as well? When they get old they can get really charred at the end and not transfer a complete spark, so you want to make sure you replace the rotor at the same time you replace the distributor cap.
Also is any smoke coming from the exhaust, does the exhaust smell of fuel once the engine is warm? If yes to both you could have some faulty injectors, or problems with the engine harness. I recently also had that problem as well as a myriad number of other problems with this damn car, and it was causing similar symptoms of stalling out at idle and a rough uncertain idle. I pulled the fuel rail, had the injectors flowed an serviced at an injector shop here in town and got a brand new fuel pressure regulator for the car. This is a bit rarer for the 2jz though as the injectors usually stay in pretty good shape unless the car sits around for a while, but it can still happen like it happened to me. So its something to consider.
And if its none of those things, and not the plugs, wires, or rotor cap then it may be time to douse the car in a healthy spread of e85 and set it on fire to collect the insurance money. This car drives me mad I swear.
03-13-16, 06:09 PM
#14
Pole Position
Join Date: May 2015
Location: CA
Posts: 208
Likes: 0
Received 0 Likes
on
0 Posts
Dude,
That is correct. As others have mentioned I would turn my attention to the idle air control valve as well as vacuum leaks. When I purchased my SC300 it would run rough and sometimes stall. I replaced the idle air control valve with a good used one and that took care of the problem.
Here's a link to someone that worked on his.
https://www.clublexus.com/forums/per...rol-valve.html
- Chester
Last edited by freakness; 03-13-16 at 06:19 PM.