Rx300 Hot Cat. Convert.

[MichiganRX300]

A great RX300 with over 260,000 on it, 1999, has served me very well. I have run all full synthetics since the "running in" of the first 1,000 miles. All fluids have been drained on regular basis and filters of course replaced. One of those guys who belives in P/M on your car goes a long way. Anyway, Check Engine Light came on, and noticed a hesitation to shift into high gear. But when car is cool, it shifts just fine. Well it then went into a "bogged" down mode, as though it were starving for air and no excelleration. RPM's were close to 3,000 w/ highest MPH apx. 40. Put it up on a hoist and found that the right cat. convt. was around 500 degrees while the left and center ones were in the 200's. So figured it was a plugged convertor. Went and bought a new one at the dealer for $240 complete wih gaskets. However when going to install the new cat. noticed the old cat. was fine, not clogged at all.

I am at a loss, please some assistance to a loyal Lexus guy in Detroit's automotive world.

[TunedRX300]

Go to Autozone and read the code out. It will tell you what is broken.

[SKperformance]

If it ran that hot it still worked quite well.

Who ever tested the temp did not understand what they were doing or else they would have told you it has to be runninhg rich.

You need to find out why that bank is running so rich.

Either a plug not firing or an injector leaking badly.

With a laser temp meter which i am sure you used you can gauge exactly which cylinder is not firing properly by a lower temp than the other 2.

It is as easy as that. But stay away from the idiot who told you the cat was bad.

[MichiganRX300]

Thanks so much for the quick replies. Autozone tester shows 1st code for O2 sensor, second code shows knock sensor, 3rd code shows same as for O2 sensor. Am I to assume it needs one or two O2 sensors? And how do I know which one to get, they said they could not narrow it down. You guys rock with the fast replies! Thanks!

[TunedRX300]

try one at a time, search for O2 sensor, there is one member "danigirl" who had multiple O2 sensors errors but it turned out to be a cracked manifold so don't replace two O2 and the knock senor in one shot. They might be caused by the same problem. I don't know enough about knock sensor but I would try to look at it first since chance of both O2 failing at the same time is slim.

[MichiganRX300]

Update.......took the codes to Lexus dealer, two "techs" and the parts manager said it was Mass Air flow sensor that could cause codes, PO171 and PO330. So got one from them, installed it, and guess what....not a @%*(*! changed. Last night took it over to a very creative buddy of mine who owns a repair shop and he said, "no big deal" and they'll fix it today. I'm wondering what he knows that the other guys do not know including the dealership. FYI, took me almost an hour to go 17 miles and would not go over 10 mph up small hills. Max speed was 30mph on downhill runs. If I pushed on acelerator beyond apx. 15% of the way down it would almost stall out too.

try one at a time, search for O2 sensor, there is one member "danigirl" who had multiple O2 sensors errors but it turned out to be a cracked manifold so don't replace two O2 and the knock senor in one shot.  They might be caused by the same problem.  I don't know enough about knock sensor but I would try to look at it first since chance of both O2 failing at the same time is slim.

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[SKperformance]

It almost does sound like a maf which is very common as well.

Like i said you have extra fuel that needs to be adressed which is going to cause an o2 sesor to run a code for being below threshold temps since the gas will keep cooling it.It will also cause the knock sensor to go off as it is not controlling the fuel to its limits.

[MichiganRX300]

It almost does sound like a maf which is very common as well.

Like i said you have extra fuel that needs to be adressed which is going to cause an o2 sesor to run a code for being below threshold temps since the gas will keep cooling it.It will also cause the knock sensor to go off as it is not controlling the fuel to its limits.

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Thanks for continued input and patience. MAF was replaced last night and nothing changed. Can't see a temp difference with laser gun on right cylinders either. Was told today that Cat. Converts. all need replacement, however cats. are now only $150ea.

I said fine, do it, must have car tonight for long business trip tomorrow a.m. in Toronto.

Does this sound right?

[SKperformance]

All cats do not go at once unless you have a really bad fuel dumping problem to feed both sides.

Also a cat is always murdered it never dies of old age.

So you have a problem that needs to be rectified or it will murder the new cats as well.

If you want drop me a line when you come to Toronto as i am here.

[TunedRX300]

It almost does sound like a maf which is very common as well.

Like i said you have extra fuel that needs to be adressed which is going to cause an o2 sesor to run a code for being below threshold temps since the gas will keep cooling it.It will also cause the knock sensor to go off as it is not controlling the fuel to its limits.

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Thanks for continued input and patience. MAF was replaced last night and nothing changed. Can't see a temp difference with laser gun on right cylinders either. Was told today that Cat. Converts. all need replacement, however cats. are now only $150ea.

I said fine, do it, must have car tonight for long business trip tomorrow a.m. in Toronto.

Does this sound right?

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Didn't you say the cat was fine? Cat is warrantied under Federal Emission Law, if indeed the cat is bad, go to dealer so you don't have to pay $150 per.

[MichiganRX300]

All cats do not go at once unless you have  a really bad fuel dumping problem to feed both sides.

Also a cat is always murdered it never dies of old age.

So you have a problem that needs to be rectified or it will murder the new cats as well.

If you want drop me a line when you come to Toronto as i am here.

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No kidding, I just you are in Missiagua, we do alot with Nova Steel and Dofasco Steel. www.gygusainc.com is our site. Small world. We also have a cottage in Sarnia on the river, great offshore boat race party every year there too 100+ people every year. OceanExpress is my uncle, inventor of first composite offshore catamaran.

Totally understood about the Cats. now....if they get it up and running I will find some time to contact you. What is best way to contact you and I'll bring the RX by too.

Brent

586-246-0799

[SKperformance]

post your email and i will send you my contact info.

Once i read it i will remove your email from the post.

[MichiganRX300]

Update from one frustrated RX owner........

OK, left off as the last posting was RX was going into local buddy, mechanic, who not only charged $300 total to fix the hot cat. problem,including cats too, but had it completed in a few hours. Great prices in my book.

With 260,000+ miles on the RX, aparently one of the cats actually came apart inside and "dumped" it's "guts" into the center cat, causing a total plug-up. Guess the engine must have felt constipated trying to expell it's exhaust.

Well, it then drives great except for it will not shift into high gear unless it is cold and check engine light came back on too. I do not know the codes yet, cancelled my Toronto trip, and thought I'd come to you guys for some more advice and insight. Plus to share what the "original" problem was relating to the hot cat and lack of speed etc.etc.

If RX is cold, it goes through all the gears just fine. Once warmed up, it will not kick into high gear--90% of the time. Any help is of course more than appreciated. Oh tranny was flushed and filled apx. 30-45 days ago too.

[SKperformance]

If it goes into limp mode it can shut the tranny down but usualyl only if it is a tranny related code not an engine code.

WOW $300 are you sure he did not just replace one cat and clean the plugged one further down?

[MichiganRX300]

If it goes into limp mode it can shut the tranny down but usualyl only if it is a tranny related code not an engine code.

WOW $300 are you sure he did not just replace one cat and clean the plugged one further down?

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He replaced the cats. I saw old ones, and saw the news ones as RX was still on a hoist when I got there, I was amazed at price differences too. What would cause a "limp" mode, I am thinking a sensor or even a plugged tranny filter. Talked with a buddy from Tower Automotive today and he said it most likely would be a plugged filter. Monday I plan to change out the filter. But will check back here for words of wisdom first.

[TunedRX300]

If it goes into limp mode it can shut the tranny down but usualyl only if it is a tranny related code not an engine code.

WOW $300 are you sure he did not just replace one cat and clean the plugged one further down?

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He replaced the cats. I saw old ones, and saw the news ones as RX was still on a hoist when I got there, I was amazed at price differences too. What would cause a "limp" mode, I am thinking a sensor or even a plugged tranny filter. Talked with a buddy from Tower Automotive today and he said it most likely would be a plugged filter. Monday I plan to change out the filter. But will check back here for words of wisdom first.

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There is no tranny filter on the RX.

[SKperformance]

There is a screen in the tranny not a filter as such since it is not a replacable or servicable part.

It could use a cleaning every so often though when flushing the fluid.

[kalo93406]

It almost does sound like a maf which is very common as well.

Like i said you have extra fuel that needs to be adressed which is going to cause an o2 sesor to run a code for being below threshold temps since the gas will keep cooling it.It will also cause the knock sensor to go off as it is not controlling the fuel to its limits.

←

Thanks for continued input and patience. MAF was replaced last night and nothing changed. Can't see a temp difference with laser gun on right cylinders either. Was told today that Cat. Converts. all need replacement, however cats. are now only $150ea.

I said fine, do it, must have car tonight for long business trip tomorrow a.m. in Toronto.

Does this sound right?

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MichiganRX... did you ever get this fixed??? I have a knock sensor open code and my car goes in to limp mode and won't shift into high gear.. I'm wondering if you have a knock sensor problem.. I also had my MAF replaced. now it runs smoother , but still have the high gear problem with the check engine light... thanks.. Roger