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Discussion Starter #1 (Edited)
i’ve seen that this code has been a pretty regular occurrence for lotus drivers, but i really need it to shut off so i can pass emissions. i’m running a stock cat with a muffler delete, and a resonator. just recently replaced the spark plugs and used dielectric grease on reinstalling the tubes, the car has 22,000 miles on it and the light has only been on for about 3,000 at most, i’ve only ever used 91/93 gas (whatever’s the best available at popular gas stations) and try to use just clean gas. i did have an issue with my MAF pigtail connector, the car had been stuttering on acceleration, and even stalling itself, for a few weeks back at 18k miles and it turned out the issue was the ground wire going to the MAF connector was chewed through/ripped... it was stored in a country barn over the winter before i bought it and it looked like a mouse or something had just chewed through that ground wire. i’m wondering if driving it like that could’ve just fried or damaged the MAF sensor? and that’s why it reads lean? spraying cleaner around the engine bay hasn’t made any differences in idle speed so i’m hesitant to say vacuum leak. possibly a bad O2 sensor post-cat? i’m new and i need help. and to be quite honest i have no idea why it reads p0420, that’s where i got the idea it might be an o2 sensor. i did buy a CEL eliminator elbow from MWR and put it on the post cat o2 sensor but it did not fix anything. which makes me think the cat is ok. the car seems to run fine, it’s still FAST as anything. i don’t notice any skipping or hesitation EVER.
but also something to note, there’s no fender liners all around the car, and the k&n air filter that was on it at 19k was almost 100% packed solid with dirt and mud. almost no airflow could get through it... that’s how stuffed it was. it had ran like that for almost two months. so i would consider the possibility, or probability of a dirty throttle body. these are just ideas off the top of my head and would LOVE some feedback from someone who knows the cars better. thank you!

edit: i replaced the k&n filter with a spectre filter on the same day i noticed how disgusting the old filter was. and it’s a snorkel.
 

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Clean all the sensors and check the wiring to the o2 sensors, maybe even check each wire with a multimeter i you know how, they get hot and damaged in that area, especially without a fender liner.
 

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Straight up, if you take that throttle body off and clean it up, ( maybe block coolant line) you will notice all kinds of sins will disappear...

I am seriously considering a vent situation to atmosphere from oem pcv setup. It would be that much less blah blah stuffing up everything.

Carbon and other buildup are my sworn enemies.
 

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Discussion Starter #4 (Edited)
thanks for the replies, i cleared the engine code when i got home on sunday afternoon, and ive put about 55 miles on it since then (35miles cruising at 65+mph) and it hasn't come back on.
i'll look into how difficult it is to clean the throttle body, and do it depending on that. i do have data logs on my phone from those (3 total) drives that i can export to iTunes and then to the internet if it will help.

this was the first time clearing the code since i put the defouler on the post-cat o2 sensor, fixed the MAF pigtail, and changed the air-filter cone. so we'll see. but i would assume that if the CEL was on for 3,000 miles that it would have shut itself off by now, if it was fine?


EDIT: i went ahead and i cleaned the MAF and the throttle body thoroughly. I'll keep you updated on the CElight / performance. thanks for the suggestion, that was surprisingly okay to do, except for the little wire holder on the bottom side of the throttle body lol
 

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Discussion Starter #5
Clean all the sensors and check the wiring to the o2 sensors, maybe even check each wire with a multimeter i you know how, they get hot and damaged in that area, especially without a fender liner.
my o2 sensor voltages look okay, and i took the throttle body off to clean out, and i cleaned the MAF sensor. but the CEL light came back on on my next drive. so i cleared it again bc i was just sick of looking at it. and then the next day i decided to remove and inspect the fuel rail and injectors, and i didnt really see much, except how much dirt the rail had on it. i didnt take any injectors off, but one of the O-Rings was folded when i put it back on, so i took it off again and put it back on properly and let it idle for a few minutes and now it doesn't read p0171 it only reads p0420. so i reset it again and i'm hopeful that since it doesnt read lean that it wont throw gas at it to "compensate" which will hopefully fix that code?
 
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