rexst

here's the background. My 1993 SC300 NA-T lay idle while I was out of the country for nearly a year. When I got back I had to do all the necessary stuff to rehabilitate the car. Replaced battery, flushed fluids, drained fuel tank and put fresh gas. changed plugs and even dissy cap, rotor, and wires. Started her up and she purrs like I just used her the day before but I have one big problem. My tach and my speedo are malfunctioning. They were perfectly fine just before I parked the car a year ago. The tach moves but is at zero when the car is idling. It's at about 1000 rpm when the car is really sounding like it's doing 3500 and at 2k when the car is at what I would estimate to be 6k. Speedo is also off. It shows 30 when i'm really going 60 or shows 40 when I'm doing 70. Anyone ever have this happen to them? I'm stumped. Could my gauges be on their last legs? Could this be a grounding problem or a shorted circuit somewhere in the engine bay. My mechanic says that my igniter might also be the cause of this problem. Could there be any basis for what he's saying?

By the way, can you guys tell me if it is normal an ignitor module to get hot. Not blistering hot. I can keep my hand on it but can definitely feel that it is almost hot to the touch after revving the car for about 5-10 minutes. I've never paid attention to this component before so I don't know if this is a normal characteristic. Oh, I also noticed that the grounding wire from the tranny that connects to the chassis was frayed and almost completely cut. Could poor grounding be causing my problems. I have since replaced the wire but have not had a chance to test the car as of yet as I was having the the tranny fluid drained as well as having the shocks replaced so I couldn't really start the car. I've always babied this car and I just want to make sure it gets back into pristine condition. I've owned this since day 1. It's a 93 with all of 26k miles on its original motor. I'd really appreciate your inputs.

Oh and lastly, my mechanic is advising me to get a new radiator. He says that there are already hairline cracks on it. The don't appear like hairline cracks but more like paint that is breaking up but I wouldn't know. I guess plastic still wears out even on a low-mileage car as it ages?

FutureSC

iTrader: (1)

Same thing with my tach and speedo, my tach is right around 500 rpm low always and the speedo is about 5-10% high. I don't know what causes it but I'd like to know too.
Then again my car is 1jz'ed so that might be an issue

cbrasian

mines did that too and now its completely out but then I'm 2jzgte swap.... I just use my navi for a general speedo

DiRocco

I realize this is an old thread, however, I am finding my 1993 SC300 is having the same issue with the low rpm readings on the tachometer gauge. Speedometer seems to be fine though, at least it reading very close to my GPS speed reading. I figured it was due to a sensor or corroded wire but I have only just begun researching the possible causes. I will begin going through my Lexus service manuals. If I find the cause, and get it fixed I will advise. If anyone has figured this out already please advise. Cheers!