WCM08

I am looking for someone familiar with the mechanics on a '92 Lexus SC300. I purchased this car about 3 months ago with 120K miles. The car has a long history of routine maintenance and appears to have been very well taken care of.

The problems began about 3 weeks after owning it. One day, I got into the car and cranked it and it seemed to muffle down and idle really rough...then it would just die and the check engine light would come on. I took the car to the local Lexus dealership and they told me it needed a new transmission at $4500, which I thought was ridiculous. The car runs fine until it decides to act up. As I pulled out of the Lexus service facility (literally...at the same time) the car started running perfect again for about 2 weeks. At this point, it would muffle down once again and it seemed like the transmission wouldn't shift...unless you manually shifted from low gears to "D"/drive. I drove the car 2 hours from my house to another shop for an inspection...the entire time it was really muffled down and sounded like an old diesel...just completely unlike a Lexus. The same thing happened again - it "fixed" itself the MOMENT I drove into the mechanic shop, however, I insisted it had a problem and them kept the car for 4 weeks and it never acted up with them so they had no clue what was going on. I would think it MIGHT be something I was doing wrong, however, I also have (2) other SC's - both '98's...one SC400, the other an SC300 - BOTH of which are 110% perfect.

...Going on. So, after I picked the car up from the shop after 4 weeks of it being there - same damn thing again...I didn't make it home before it started acting up again. At this point - I took it to BIG 10 TIRE'S here in town (they have a foreign car mechanic) and they did the following work;
-Installed new Catalytic Converter
-Installed new spark plugs & wires
-Checked the timing
-Performed full service

The work (above) seemed to help the low idle problems upon cranking the car, however, now - after driving it a while...it will start idling rough once again and I was told that the Upper Radiator Hose sucks together after the car has ran for a while. Now BIG 10 has thrown their hands up and said "I don't know"...

I don't know what to do and would appreciate ANY advice/help/direction that you may have.

Thanks
-Jason

masagsxr

The mechanics are usually dead on with their diagnostics granted that you even took it to Lexus Dealership. Instead of spending $4500, maybe you can buy buy a used tranny then DIY or get a local shop to install it for yah.

Good luck.

WCM08

I forgot to mention in the post that I took the car to another Lexus dealership out of my area and they said the transmission was OK. I really think its going to be some sort of mechanical issue because the car operates perfectly when it wants to...then idles horribly and drives bad on occasion. Any idea if it could possibly be an ECU module somewhere that's gone bad? I am clueless...

Thanks for your help

masagsxr

I doubt its the ECU. Besides, the ECU really does not go bad just like that. You mentioned that sometimes you have to have the gear on L all the way to D so your tranny is probably going bad.

WCM08

Today I picked it up from the mechanic shop once again (I don't think they know what they're doing) and they replaced the radiator hose because the old one apparently would suction itself together after the car was driven for a while. So, they replaced the hose with one that has a metal structure to keep it from sucking itself together.

I drove the car for about 30 minutes and it did fine, then - it started vibrating pretty badly and sounded like a lawn mower (weird noise). Maybe more like a gas-power generator sounds, regardless - certainly not what is suppose to sound like. Anyway, as it makes this sound...the car drives very rough. You can fix this, however, by (literally) pressing the gas to the floor and speeding. The car smooths out if you drive it like a bat out of hell, I'm clueless to whats going on.

Do you think its possible that the wheels could be causing problems in the computer system? When I bought it - I took off the old 14" wheels and installed the pull-off's from my '98 SC400 (which were a size or two larger). It may not have anything to do with it, just curious.

Thanks again for your help

masagsxr

No problem man but i'm afraid i'm to say i'm not that much of a help. I'm only responding from your comments and what the shops tell you. I'm not a mechanic or everything but I have the passion to learn and have always done all if not most of the work myself. Not having a lot of $$$ to spend is also a plus so I have no choice to figure things out on my own.... I'm surprise there aren't any other gearheads contributing to this.

I still think its the tranny since you said that sometimes you have to go all the way to L >> D. How does the car run/idle when it is just on PARK or NEUTRAL? Maybe drive it for a while and when it starts to make noise, put it on neutral or park and see if the car runs/idles normal.

RyanJBuell

I also have a 1992 SC300 (manual). I am told that I need a new transmission, but I wont spend the money for that. I replaced my mass air flow sensor, and that helped (50 bucks off ebay). Now when I start the car, it might be able to idle by itself for a few moments, but then it will die. I also have to physically keep the car from dying by holding down on the gas. I don't know the answer to the problem yet, but I will let you know when I figure it out.

Shanty

I'm having the same issue as well. I've got a guy who's really well versed in Toyotas who will be looking at it tomorrow. I haven't replaced MAF sensor, but I'm considering it. Actually I'm considering having someone else do it.

Harbinger

Doesn't sound like the tranny @ all. The MAF sounds like an excellent place to start considering everything that you've done already. Since you mentioned you were having issues with the radiator hose, I'd bite the bullet and check your other vacuum hoses as well. Other culprits could be a bad O2 sensor or crank position sensor. I've had both create a similar issue on various cars, but they typically throw a code and show up on a diagnostic.

lexdud

OP,

Question: Does the car "act up" when in park (not in gear)? If it runs rough both in and out of gear then it is probably not the transmission. I have a '93 SC4 and went through (literally) hell fixing my car with a no-idle problem. The car would run just fine if you depressed the gas pedal but would not start nor idle. I was told by the Lexus dealership that the problem was the IACV ... and if that failed to fix it the ECU was "shorted out". I replaced the IACV with a used working unit to no effect. I then bought a used working ECU for the car and that finally fixed it.

If your problem happens while idling (in Park) try cleaning your IACV. Search the forum for an article by The Mole on doing it for the SC3.

Good luck ...

bacaudio

I would try a self diagnosis which can be found here:

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

lexdud

This is a GREAT link for reading OBD I codes.

Thank you.

But what if the car is throwing no (zero, 0) codes? My car wasn't when it had it's no-idle issue.

95lexsc300

so what was the problem on your sc

MIGS

iTrader: (15)

wow, OP, i have almost the EXACT same problem with my car/idle.

i had a local shop check my car and they plugged up the scan tool. they told me that my ecu was bad and needs replacement.

today i changed my ecu hoping it would fix everything. i'm gonna drive it again tomorrow and the rest of this week to see if the problem returs.

Question: does your exhaust blow white smoke out the back when it idles rough, like mines?

Willdrift1

did you every figure out the problem?