Hey Guys,
First and foremost, I want to say that this site is THE BEST site for getting info on Lexus cars. Great job fellas. I dont post too much.. I guess you could say I just browse mostly. As I learn more about my car I will post more.

Heres my issue.. I have a 92 SC300 with 70k. About a week ago I started to experience rough idle and white exhuast with a smell of unburnt fuel. It would go away as I pushed the gas. The car died on me so I had it towed to my house. I changed the plugs, cap, rotor, and wires. while doing so I noticed the #5 plug had some carbon build up on it. The throttle body had tons of carbon build up as well but I was told by Lexus thats what happens to a car of that age, it just needs to be cleaned. Anyways the car started after plugs and wires were installed. Now the hesitation is constant. Sounds like Im running on 5 cyl.

I took the car to a local gas station for diagnostic check (big mistake). They told me that the #5 injector shorted out and also grounded out my ECM. $2000 to fix I thought to myself, better get another opinion. So I called lexus and the tech told me that ECMs on the sc rarely go bad and if it was bad the car would not start period. I figured I'd have the car towed to Toyota of Irving to see what they say. There gonna call me on mon with the results.

Here are some of my thoughts:

Headgasket- The car only has 70k! I checked the antifreeze (green as can be) and the oil is normal color.
TPS- Maybe.. Not sure. I dont think exhaust smoke is a syptom of a bad TPS.
Mass airflow sensor- nope
Fuel pump- checked (good)
Timing belt- Not sure.. (Looks to be in good condition but you can never tell by just looking)
Fuel Filter- nope

Do any of you have an idea as to what is going on?? Your insight would be much appreciated.

By the way I searched this whole site for this problem. No real answers.

 

check the intake tube from the MAF to the intake and inspect for breaks, cracks, or other leaks.

 

Thanks for the reply...

Already done... The rubber piece from throttle body was cracked from age but I replaced it.
No change.

 

I had the 42.5 mph hesitation (stilled not cured). During my timing belt change I adjusted the TPS. I did not adjust it right the first time and when I started the engine it did not want to run. Because of all the things I had just worked on Belts,rollers,WP,Rotor,cap,wires you name it, I thought the worst. As it turned out I re-adjusted the sensor and everything is working well. The adjustment is in the book. If you want information on how to adjust let me know.
David 95 SC400

 

Man.. I wish that was all I needed but the white smoke has got me worried.
Thanks David I'll keep that in mind.