Mechanics

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1993 Lexus LS 400

Engine Performance problem
1993 Lexus LS 400 V8 Two Wheel Drive Automatic 217000 miles

motor is a 1uz-fe v8 overhead cam 32 lexus. Car has been maintained properly throught the years was running Great! All of a sudden on the way home from work it loses half it's power. It accelerates fine in park but notice some things engine sounds muffeled. And a bad smell. And rattle on the right side of engine compartment. Sound maybe coming from underneath the car. It doesn't really act like a normal misfire or plug. Acts like it's running on half the cylinders. Can the cat conver cause this kind of loss? I was able to reaCH Hwy speed but sluggishly.
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Mark frizzell
July 19, 2008.




Hi Mark,

Thanks for the donation.

Yes, if the cat converter is clogged, it would cause insufficient exhaust flow. When no load revving, you would not notice much difference. Going at higher rpm on load, the back pressure would cause insufficient airflow into the cylinders from the intake resulting in very bad performance.

The bad smell and muffled sound is similar with a failed cat converter.

KHLow2008
Jul 20, 2008.
Thanks for the answer!
Also is it possible that if this the case it could have damaged th the 02 sensor and anything else associated with the exhaust monitoring system? And I can't find a repair manual for this lexus thats not the $200.00 OEM. Know of any others?

Thanks,
Mark
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Tiny
Mark frizzell
Jul 20, 2008.
Hi Mark,

Before the catalytic converter fails, it might have operated at a very high temp, even glows red so it could cause the O2 sensor to fail. Any misfiring of engine cylinders could be the initial cause.

Sorry I have no idea of after market parts, maybe you can try Autozone and see if they have any.

KHLow2008
Jul 20, 2008.
Yes the converter was clogged, so bad it blew a chunk of it out and logged itself against the senser.
I know it is unlawful to remove the converter due to emission laws, but my question is if there was no converter would the engine run incorrectly, or would the sensors readjust for the change? Hypothedicaly.
There is a sensor before the cat. And one after, 02 and? What is the other. Pressure?
This concludes my questions u have been a great help, WORTH EVERY PENNY!

Thanks Mark

Tiny
Mark frizzell
Jul 20, 2008.
Hi Mark,

You are welcomed.

Without the cat converter, the car would still run well but the check engine lights would show sooner or later. You would also fail emission.

Both are known as HO2S (Heated Oxygen Sensor), only difference is front and rear. The front sensor is to monitor the exhaust gas and and inform the ECM to make the necessary adjustments and the rear is to monitor the catalytic converter efficiency.

You are welcomed to drop by any time you have a question.

Have a nice day.

KHLow2008
Jul 20, 2008.
Need more help here. I have repaired the converter, replaced the h20 senser, car does seem to be missing. My mistake. Is it possible something happened and this caused the cat to fail, which in turn damaged the sensor? Car runs real rough(bad) smell raw gas out of exhaust, ECM maybe failed? If so where is it located? Please read back through the thread maybe u can give me a few things I should look for other than the obvious, it seems to be missing on the right bank of the engine, at start up if u rev it alittle it pops back ( just once ) as it warms up it quits. But still seems to be missing.

Thanks, Mark.

Tiny
Mark frizzell
Jul 21, 2008.
Hi Mark,

If any of the cylinders is misfiring badly, it could cause the catalytic converter to glow red hot when rich fuel is pushed through it for a period of time. That could be the initial cause of the catalytic converter failing.

Should be an electrical fault as fuel is present.

Check the spark plugs and related parts. Compare the 3 plugs of one bank and see if the color of the plugs tips and ceramics are similar, the one that looks sooted should be the main culprit. Compare them with the other bank of 3 plugs to get an idea what it should look like.

If all looks sooted, you need to replace them.

KHLow2008
Jul 21, 2008.
So, ur saying that It could be just a fouled plug?Or two becuase it seems directed to only one side?
Not the ecm?

Tiny
Mark frizzell
Jul 21, 2008.
Hi Mark,

Yes, that is possible.

The ECM is a reliable component the chances of it failing are minimal.

Btw is the CEL still showing? If yes, what is the error code?

The other possible reasons are bad injectors, allowing more than designated amount of fuel to go through.

Bad igniton coil or wires could also cause it. Check for oil or water in plug holes.

KHLow2008
Jul 21, 2008.
Well after digging a little deeper. I found that the left bank distributor was not firing and the car is running on the right bank Dist only! (4 cyl's!).
Now I have determined that there is no fire from the left bank coil! Other than 12 volts is present. My question is. Is there anything other than just a bad coil at this point is there anything that would not allow the coil not work? There is 12 volts passing thru it, but no high voltage coming from it.

Tiny
Mark frizzell
Jul 23, 2008.

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