Initial Impressions of my '95 and p0420/p0430
08-02-15, 04:11 PM
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Initial Impressions of my '95 and p0420/p0430
Picked up a 95 LS400 with 192k miles about a week ago and overall I'm pretty impressed with this car, good ride, transmission shifts smooth, keeps up just fine with highway traffic.
my only issues so far are a p0420/p0430 codes that popped up the other day, i reset them but they came back, overall performance of the vehicle doesn't seem to be suffering too much. I know these codes are for the cat converters on bank1 and bank2. a little reading has led me to believe that they may not actually be bad and it could be an exhaust leak instead, I've also read that an o2 sensor could possibly cause this? I'm not familiar with gasoline engines newer than mid 80's or so, so i'm still learning, please interject corrections if i'm mistaken on anything.
my fuel mileage also seems to be fairly poor, not much better (or better at all) than my old 99 cummins which seems a little low for a japanese engine, even if it is a V8. 13 mpg combined seems pretty poor to me, could the p0420/p0430 codes be dragging down my mileage?
according to the previous owner all timed maintenance is up to date (water pump and timing belt were done 30k ago) but i would still like to get ahead and maybe improve driveability/power/mileage if i can which leads me to this list:
1. running a few tanks of high grade premium fuel through to try and clean up the system if i can. is there a recommend fuel system cleaner that i can run in the fuel and hopefully breathe some life into it?
2. how important is it to immediately fix the p0420/p0430 codes?
3. i was planning on changing out plugs and wires, is there a be-all-end-all brand and style that run well in these lexus? while i was doing that i also planned on changing out the coolant temp sensor, i read through a long thread on that and figured it was worth a shot, cheap, and easy.
4. i read through the first 14 pages of the ECM capacitor replacement thread, i do plan on doing this eventually, the sooner the better, but do not have the time or resources to do it at the moment.
5. any other suggestions are welcome, thanks in advance.
my only issues so far are a p0420/p0430 codes that popped up the other day, i reset them but they came back, overall performance of the vehicle doesn't seem to be suffering too much. I know these codes are for the cat converters on bank1 and bank2. a little reading has led me to believe that they may not actually be bad and it could be an exhaust leak instead, I've also read that an o2 sensor could possibly cause this? I'm not familiar with gasoline engines newer than mid 80's or so, so i'm still learning, please interject corrections if i'm mistaken on anything.
my fuel mileage also seems to be fairly poor, not much better (or better at all) than my old 99 cummins which seems a little low for a japanese engine, even if it is a V8. 13 mpg combined seems pretty poor to me, could the p0420/p0430 codes be dragging down my mileage?
according to the previous owner all timed maintenance is up to date (water pump and timing belt were done 30k ago) but i would still like to get ahead and maybe improve driveability/power/mileage if i can which leads me to this list:
1. running a few tanks of high grade premium fuel through to try and clean up the system if i can. is there a recommend fuel system cleaner that i can run in the fuel and hopefully breathe some life into it?
2. how important is it to immediately fix the p0420/p0430 codes?
3. i was planning on changing out plugs and wires, is there a be-all-end-all brand and style that run well in these lexus? while i was doing that i also planned on changing out the coolant temp sensor, i read through a long thread on that and figured it was worth a shot, cheap, and easy.
4. i read through the first 14 pages of the ECM capacitor replacement thread, i do plan on doing this eventually, the sooner the better, but do not have the time or resources to do it at the moment.
5. any other suggestions are welcome, thanks in advance.
Last edited by RA40; 08-03-15 at 01:08 PM. Reason: title adjustment
08-02-15, 10:44 PM
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update: took it for a drive tonight with less traffic and averaged about 20 mpg. much better than the 13 before. i had refilled it with shell 91 octane which seems much better than the Circle K junk i used before. still would like to run some fuel system cleaner if that offers any benefit.
08-03-15, 02:36 AM
#3
An important sensor that seems to go bad and cause problems is the engine coolant temperature sensor.
A scan tool that reads real time info is a help when you have codes that are fuel and emissions related.
A scan tool that reads real time info is a help when you have codes that are fuel and emissions related.
08-03-15, 04:16 AM
#4
1. running a few tanks of high grade premium fuel through to try and clean up the system if i can. is there a recommend fuel system cleaner that i can run in the fuel and hopefully breathe some life into it?
2. how important is it to immediately fix the p0420/p0430 codes?
3. i was planning on changing out plugs and wires, is there a be-all-end-all brand and style that run well in these lexus? while i was doing that i also planned on changing out the coolant temp sensor, i read through a long thread on that and figured it was worth a shot, cheap, and easy.
4. i read through the first 14 pages of the ECM capacitor replacement thread, i do plan on doing this eventually, the sooner the better, but do not have the time or resources to do it at the moment.
5. any other suggestions are welcome, thanks in advance.
2. Those codes don't affect the engine performance or gas mileage, its just means your converters are performing below 95% efficiency probably from slightly clogged mesh screens with carbon build up. You could drive your car for years without any problems but your car won't pass inspection obviously , I did have these codes and got rid of them but you might think I'm crazy if I told you my method how I did it.
3. For spark plugs and wires use NGK or Denso can't go wrong with either one. Also change PCV valve and grommet its cheap and easy to do. If you want to, replace the distributor caps and rotors and air filter.
4. I don't think you need do that just yet.
5. Use ONLY Type IV Toyota transmission fluid in the tranny, a simple drain and refill. If you replace motor and transmission mounts use only dealer parts.
Last edited by LsG86; 08-03-15 at 09:06 AM.
08-03-15, 01:25 PM
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1. I like Gumout products personally. I think their best cleaner now is "All in One" fuel system. I hear Chevron is good too.
2. Those codes don't affect the engine performance or gas mileage, its just means your converters are performing below 95% efficiency probably from slightly clogged mesh screens with carbon build up. You could drive your car for years without any problems but your car won't pass inspection obviously , I did have these codes and got rid of them but you might think I'm crazy if I told you my method how I did it.
3. For spark plugs and wires use NGK or Denso can't go wrong with either one. Also change PCV valve and grommet its cheap and easy to do. If you want to, replace the distributor caps and rotors and air filter.
4. I don't think you need do that just yet.
5. Use ONLY Type IV Toyota transmission fluid in the tranny, a simple drain and refill. If you replace motor and transmission mounts use only dealer parts.
2. Those codes don't affect the engine performance or gas mileage, its just means your converters are performing below 95% efficiency probably from slightly clogged mesh screens with carbon build up. You could drive your car for years without any problems but your car won't pass inspection obviously , I did have these codes and got rid of them but you might think I'm crazy if I told you my method how I did it.
3. For spark plugs and wires use NGK or Denso can't go wrong with either one. Also change PCV valve and grommet its cheap and easy to do. If you want to, replace the distributor caps and rotors and air filter.
4. I don't think you need do that just yet.
5. Use ONLY Type IV Toyota transmission fluid in the tranny, a simple drain and refill. If you replace motor and transmission mounts use only dealer parts.
I'm making the person I bought it from fix the CEL codes for me so I don't have to worry about them or look at the light anymore.
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