$275 '00 Lexus ES300--P0420

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TXCarGeek

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Bought a 2000 Lexus ES300 two months ago for $275...clean interior, minor battle scars on the exterior, no rust, overall, quite serviceable and not embarrassing to be seen in for being completely torn up and looking like a clown. Anyway, 3 coils were dead when I picked it up, got that fixed up and it really made it run well. Had a knock sensor code which I took care of to get it out of that limp home mode that also prevented it from shifting into 4th gear. Once that code was cleared, I got a p0420 pending code that eventually triggered the dash light.

As of now, tomorrow I'm going to check for exhaust leaks before the cat. Seems some have talked about fuel pressure possibly causing issues so I'm going to check that too for good measure. On my scanner, I noticed that the long term fuel trim for bank 2 was sitting at around 10.0 while it was around 1.8 for bank 1...unsure if that can be related to this specific code as I'm a bit ignorant when it comes to diagnosing issues using live data from a scanner although I've been reading as much as I could. I've seen lots of folks talk about the O2 sensor behind the cat being a potential culprit; I understand that O2 sensors should fluctuate back and forth between from around 0.1v and 0.9...I have yet to check that and will report back what I find. Also, seems like the A/F sensors right off the exhaust manifolds don't usually trip this code so I'm not too worried about them.

Am I going in the right direction in my troubleshooting before throwing in the towel and potentially replacing the cat? Am I missing anything else?
 
Some people have been known to use spark plug anti foulers. If they're rusty they pass visual inspection.
 
I think checking for a exhaust look is a good idea as that could be what's causing both your issues (ur LTFT is high). But, don't NOT check your sensors. Bad O2 sensors either upstream or down can contribute/be the cause of your p0420. (google bad o2 sensor and p0420)

Plus, your LTFT being high (should be no more than 8) means you def want to make sure you don't have a bad upstream sensor. (but a high positive# LTFT, is usually a vacuum leak or fuel delivery problem)
 
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I hope you didn't buy someone else's money pit.. the $275 price has me worried.
 
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Originally Posted by Mad_Hatter
I hope you didn't buy someone else's money pit.. the $275 price has me worried.


It sounds like he's been making great progress bringing it back to health so far.... probably not much into it, and having a good running car.
 
Dont know where you can get a car for that cheap, wreckers will pay that much here if you drive it in.

You can learn alot from LTFT a quick google will give lots of additional information in how to use it to help you diagnose.
 
Originally Posted by eljefino
Some people have been known to use spark plug anti foulers. If they're rusty they pass visual inspection.


I will vouch for that. Personally
thumbsup2.gif


Easypeezy $10 experiment.
 
Well, I'm not much of a toyota guy, in my mind 0420 is catalyst below efficiency. Says that the post-o2 sensor isn't reading expected. Bad cat? Exhaust leak? Bad post cat o2 sensor? Or is it upstream from various reasons causing running too rich, from air intake, bad spark?

I.e. I would have expected exhaust leak or bad cat with that isolated 0420 code. However, since your coils were bad and your fuel trim was off, it may be been long term misfiring during previous ownership that killed the cat.

Not sure what you want to do or spend on a $275 Texas car. Others have already mentioned cheap ways of masking the "perceived issue" and getting rid of the cel. Depends on how much effort and money you want to go towards making a real diagnosis, and then once you find the cause, is the cost of fix worth it?
 
Thanks for the plethora of replies thus far.

Worth mentioning that I'm in a non-emissions county in Texas. Got it inspected yesterday and passed with the CEL on in fact. I've seen the anti fouler trick...may go that route tbh.

The coils I picked up at a pick n pull...believe that came out to $26 total for three. I really don't have much into it...probably right around what I paid for the car.

I picked it up from an acquaintance of mine that just didn't want to spend money on it any longer and didn't have time to repair it himself.

If I remember correctly, there two bad coils in the front(bank2) and one in the back(bank1).
 
Well, drove it around some more today and the fuel trims seemed okay. At idle, they were all under 4.0. I cleared the code yesterday and I'll see if it returns.

I did notice though that past 4k rpms, it seems to really not want to rev out freely. I have a friend of mine with a muffler shop so if the light returns, I'll take it to him and have him test to see if the converter is actually clogged.
 
That engine has a variable intake runner doohickey-- check to see if that works. The $15 ebay techstream thingie should be able to activate it to test it.
 
I'm leaving out of town tomorrow and would like to see if I can check it now before I'm gone.
 
Originally Posted by Mad_Hatter
I hope you didn't buy someone else's money pit.. the $275 price has me worried.


6 OEM coils probably cost more than $275 and the previous owner may have sold it for that reason alone. Should always replace all coils at the same time, BTDT. And with good quality OE units, optimally.

P0420 try a clean of the cat first, also, can make it go away if dirty and that's the issue
 
The coils were replaced with Denso coils that I pulled from a pick n pull. Runs just fine and I have zero ignition related issues.

Also, checked that variable intake runner deal on the engine just now and the vacuum actuator is operational...blip the throttle all the way quickly and it acuates just fine.

So for now, I'm likely going to just install that non-fouler in hopes that it will at least keep the light off and then whenever I get back from my trip, I'll have my exhaust guy check for pre-cat exhaust leaks and for a clogged cat.
 
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Originally Posted by TXCarGeek
Well, drove it around some more today and the fuel trims seemed okay. At idle, they were all under 4.0. I cleared the code yesterday and I'll see if it returns.

I did notice though that past 4k rpms, it seems to really not want to rev out freely. I have a friend of mine with a muffler shop so if the light returns, I'll take it to him and have him test to see if the converter is actually clogged.




Big improvement and more where they should be.ðŸ‘
 
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