mrwinkle

Hello guys and gals, I have been having this issue with my 1990 lex ls400 for about three weeks now. I took off the throttle body, cleaned it, and the intake and i still have this problem. Do you think the throttle position sensor is the culprit? PLEASE WATCH THIS VIDEO BELOW. It will explain it a whole lot better than me. Thanks in advanced

http://www.youtube.com/watch?v=NntNW4v8eA8

91LS400vgb

I would start by retrieving the diagnostic codes:

http://www.lexls.com/tutorials/intro/codereading.html

steve2006

Check the IACV

deanshark

Like steve said, check the IAC. Check out the threads that come up with the search feature with "IAC valve" as title. They'll tell you how to check it, clean it, and even rebuild it if you need to. You should also pull the codes (Engine and ABS) that might tell you exactly what the problem is. But in the video it does sound like the IAC valve.

mrwinkle

is there anyway to rebuild the iacv and is buying used ok?

oldskewel

iTrader: (1)

I have not had problems with the IACV on my Lexus, but on other cars have had success in just cleaning it carefully with brake cleaner and q-tips. I think sometimes they just gunk up and stick.

The tips by the preceding posters are exactly right. Get the codes figured out, and search for info on how to clean the IACV.

mrwinkle

okay cleaned my iacv by use of THIS
. okay when i take the main hose off of my IACV i hear it sucking in a ton of air, which i beleive it should when the car is idling since the throttle is closed. So could this rule out my IACV. I should have took pics to show how good i cleaned it but is pretty darn clean. It has not a lick of carbon on the nipple that goes into the intake and none of my bearings are frozen or freezing up. Could my TPS be my villain?

deanshark

Did you test the IAC while you had it out to make sure it opens and closes correctly? Here's a link to checking the TPS and AFM. https://www.clublexus.com/forums/sc-...on-issues.html

91LS400vgb

Did you check for codes? I think it's prudent to do that first. It may not have any, but if it does, then it may give you a clue to point you in the right direction with less guess work.

mrwinkle

Okay check the codes and now this plot of this story has taken another turn. I got code 13 - RPM signal no. 2 and code 52 - No. 1 knock sensor signal. Now the check engine light has been on since i bought the car, I had her timing belt and water pump changed but she ran fine up until now. So does this rule out the TPS and IACV and have the cam sensor and/or knock sensor signal been behind this the whole time?

Abdiel

you can go to your nearest pick and pull and find the same year and it will work and run fine. havent had any problems with mines since i did it. save a few hundred bucks

mrwinkle

are you talking about the cam and knock sensors?

pearl93'ls

acts just like mine!

Abdiel

my problem was the idle control valve.

vaughn37

If you go replacing the knock sensor sensor's.Make sure it is not the wiring harness.If it is you can buy it for like 50 bucks from Sewell Lexus.don't let some Lexus dealer tell you that you need the whole engine harness.

And if it is a sensor only buy the Toyota brand. the car does not like aftermarket sensors