chinaman

I just purchased a '94 LS400 two weeks ago. It rides like a dream, but yesterday
it started hesitating in idle. Found out TPS sensor wasn't screwed in. I tightened the screws on TPS and it idled a little bit better. Took it for a test run and the car had no power at all. Had to almost floor it to get it to move and also it revved higher than before, seems like it took longer for transmission to change gears. Then I found out catalytic converters were running red hot which caused smoke everywhere. Check engine light came on for a couple minutes, I am taking it to Autozone tomorrow for a diagnostic. Possible clogged catalytic converters? I need help diagnosing problem and where to look?

DriftGirl

iTrader: (6)

clogged...bad

could be dumping raw fuel into them...which will ruin them the fastest.

Did you check the air sensors? what color was the smoke?

Anyway, The converter is ruined if it heated up 'red'. Theres no 'saving them' once they heat up like that. Remove it(them) before it ruins the engine...

PureDrifter

iTrader: (10)

yea, 2 dead cats (best replaced in pairs).

chinaman

Just pulled a code, code 25, air/fuel ratio lean malfunction
U guys think its the cat? Or problem with sensors? Help?

chinaman

And the smoke was white, I think it was just all the heat from the cat

DriftGirl

iTrader: (6)

air sensors. Replace all of them.

You may as well get performance CATS. They're cheaper than OEM...and perform a lil better.

Dont run the car in its present condition tho. It can cause ring failure (and other crap) from dumping raw fuel out the tail pipes. This is shown by black smoke first. The white smoke troubles me tho, you may wanna compression check after replacing the cats and sensors.

oh, change the oil

pito

Hold your horses guys.

Try this. I had the exact problem you are having. Out of the blue car was running. Then ran like crap no power, red cats blah, blah, blah.

$1300 later find out that the driver side igniton coil went bad. Please check your coils before you go spending like a fool. The sensors will read bad because it is reading false information. My oxygens sensors were reading wrong so I changed them, guess what.....Car still ran like ****.

CHECK THE COILS MY FRIEND. THANKS TO CRAZIMOFO AND DAMN FORGOT THE OTHER GUY SORRY. BUT HE POINTED ME IN THE RIGHT DIRECTION.

DriftGirl

iTrader: (6)

Yeah, that could be a problem as well. But anytime a cat glows...its lining has fused and heated up. They will not work as intended from here on out.

A bad coil(s) CAN cause those problems. Ive had an aftermarket (MSD) cause the same situation. I leaned away from thinking it was exactly the same because it would continue to give black smoke on a bad coil.

Maybe others have had a different experience??

IMHO, its better to fix what you know is wrong, before 'throwing money' and 'time' at a problem and hoping for a fix.

TJW98LS

iTrader: (1)

Wow, I learn something new everyday. I've never heard of a cat getting red hot before. You should know that any part of the car the glows red hot will be completely ruined...that's the point at which metal starts to melt!

PureDrifter

iTrader: (10)

the burning cat is a symptom of a bigger problem

fix the cats.
then have ur ign. coils tested (dont drive car until ur done with all of this)

if they all test out replace MAF.

GRAND_LS 4

iTrader: (2)

Let us know the codes before you start changing things. Im guessing its o2 sensors since a code was thrown. Or the TPS sensor.

chinaman

I'm going to test ignition coils tomorrow. The only code was Code 25, and it was only on for a couple minutes. It came on when I put it in neutral and started revving the motor because it wasn't giving me any power. Any one have links on how to test MAF and TPS?

chinaman

I tested both ignition coils several times with two different meters and I always get .7 ohms, which is outside of specs. Is it a coincidence both are reading the same? Also tested MAF and is within specs.

chinaman

OK. Just went to Autozone and they said both ignition coils are OK. Dont understand why my readings are different than theirs??

crazimofo

chinaman im in the same boat as you!

did you check your tps sensor if its in specifications, being that you had to screw it in?

i have the same problem with 2 brand new ignition coils and 4 new oxygen sensors. new spark plugs and wires.

i wonder if its the cats clogged? or it might be the y -pipe that the cats connect to sometimes that gets clogged at the junction where they split.

code 25

let me know what you find out.