Hi,

Tried to turn on my car the other day and it started fine and then suddenly the rpm gauge dropped and the car shut-off. Did this about four times before the car finally started -- I could definitely feel the powerless (exhaust sounded louder and deeper). On the highway, the car was very sluggish -- max speed of about 60ish, even with the pedal floored.

When I got home, I saw smoke coming out from the passenger side of the hood and looked under the car to find what appeared to be part of the exhaust glowing red.

I've read quite a bit on the forms with other members facing similar issues. It sounds like people are usually doing a tune-up or changing the catalytic converter.

Just a little background, I did a full tune-up on my car at 160k (currently has 170k) -- sparkplugs, wires, caps, and both ignition coils. I ran into similar power loss back then -- which is why I did the tune up.

Where should I start to diagnose the problem if I've already had a tune up done? Should I change the catalytic converter and see what happens? Are there other (simpler) troubleshoots? Also, is it hard to change the catalytic converter (did the tune up myself)?

Any help is appreciated - I've got to get the car running this weekend.

Thanks

 

Not saying cats are your problem, but if you decide to check/change the cats here's a good writeup on it.
http://www.lexls.com/tutorials/exhaust/fpipe.html
I have a 92 SC400 w/ ~180K miles & both front cats had significant melted/broken interior honeycomb catalysts when i got it. I resorted to hollowing them out since Florida doesn't have emmision testing. Some of the upper nuts on the cat flange are in very tight quarters so be prepared. I remember alternating between 3/8 & 1/2 deep sockets & box wrench to get these off. AND be sure to PB blast all those fasteners a day ahead to let it really soak in there. You don't want to break any studs or strip any threads as it just will add to your task.

 

thanks for the the info man -- although it doesn't appear difficult, the task looks messy without a lift. If I do decide the change them, I might just have to take it to the shop..

anyone have anyone suggest any other avenues besides changing the cats?

 

To me it sounds like the cats to much restriction, clogged (back pressure) is bad. I'd inspect them

 

this might be a stupid question -- is the only way to inspect them by removing them??

is there a "test" i could possible do to make sure?

 

just got back from the shop...the machnic hasn't yet put it on lifts but was like "cats just go bad like that, we have to fine the root cause"

After I told him that I changed the the, plugs and caps..he said it might be the timing belt -- it might have "jumped."

Is that possible? Would it cause power loss and cats to glow?

 

I doubt the timing belt jumped I'm really leaning towards the cats, had it happen to a few people. But if you want you can check the timing to be sure to urself. Also is the 300 or4?

 

thanks -- it's a sc4. Will call the shop tommrow and provide an update....i really HOPE it's just the cats.

Does anyone know how much I should expect to pay?

 

Change your engine Coolant Temperature sensor and your problem with power loss will be solved. It fixed my problem. and I have changed everything under the hood almost. FP, Filter, Plugs, wires, Dizzy cap/ rotors...MAF cleaned, TB cleaned, new TPS, EGR cleaned...nothing seemed to cure the loss of power issue until I changed that Temp Sensor.. just got back from a 600 mile round trip about an hour ago..I had to tell the world this because I have yet to find a post that says """"FIXED""""" .. Start there.. It may or may not work but its worth the 13.99 I paid for it at Autozone.

 

Thank you!! As an update, my shop sent it to the lexus dealer wanted to start with the plugs/wires...knowing they have been changes.

I will talk to my shop tomorrow and mention the coolant temp. sensor. I did notice that the orange radiator light had been turning on randomly lately-- this may be my fix...fingers crossed.

 

I hate mystery problems--------fxxxing hate them--

Good luck

 

****IGNITION COILS****

Check them, NOW! They go bad causing gas to get in the cats causing the cats to get hot, they happen instantly and cause a shakey idle, about a 40-60mph max speed, and the rpm gauge just drops.

Just find a new one and test both of them with the new one, one at a time, all you have to do is set the new coil somewhere and plug it in.

 

got the car back today.

The mechanic first tried the fuel pump -- didn't work. Only charged me for the part and not labor.

He sent it to Lexus for diagnostic -- towing and diagnostic was close to $300.

Lexus wanted $500 for each igniter -- parts alone. Mechanic found them at a junk yard and changed both.

Everything included --- set me back $800!

At 170k, is the car getting too expensive to maintain? I LOVE it and DO NOT want to give it up...

 

i'm having the same issue... All i did was change the spark plugs and now this power loss really got me worried.. idk if i'll be able to make my road trip from ny to kentucky.. But thanks to you guys,, i'm gonna check the ignition coils and the engine coolant sensor and see if i get anywhere... I also have that big drop in the rpm whenever i take my foot off the gas... i knew that wasn't normal.. I was scared to even go to 40mph,, but i made it there and i'll try 50mph later.

 

where is the engine coolant temp sensor located?