Hey guys, so I recently got these codes, including the P0101. I went ahead and replaced the MAF sensor, not OEM though, but the codes came back. No clue where to go from after here. Would a Denso MAF fix the problem? Would the aftermarket MAF I put in maybe not work well with my system?

Please let me know what might be up. Thanks!!!

 

The MAF is one of those parts that you always want to go with OEM. Rockauto.com has them at greatly reduced prices compared to the Dealership.

 

Did you reset the ECU?

​​​​​​Disconnect the negative on the battery for 20 minutes.
FYI the car willstart and sputter on first try it's normal. Start it back up.

Let it idle until the cooling fans kick on at about 205F. Don't touch the gas pedal
Then shut it down for a minute or so. Start it back up and go drive around. You'll have to drive around for like 50-100 Miles till the ECU learns again. It's on a clean slate.

How's your air filter? I'd replace it if it has more than 12k on it. Try cleaning the OEM MAF you took off first with CRC MAF cleaner. Does your car feel like it wants to stall? Tell sign of a bad MAF. It will have some hesitation and it will sputter at low rpms. Probably get some backfiring too occasionally.

Anytime you replace critical components you'll want to wipe the ECU by erasing the LTFT. This happens by disconnecting the negative on the battery.

 

Gotcha, I'll check it out and see, thanks!

 

So I believe I did, I had disconnected the battery let it sit for a while, then plugged it back in. Then I did let it sit idle, but I don't think I waited until the fans kicked in. Then I basically drove about ~140mi. Or so. It wasn't until I was at a stop light close to my destination that the lights came on again. Air filter was replaced, and I got the "new" MAF sensor since I got a P0101 code and the sensor itself was going bad too.

 

Check for any vacuum leaks. Starting with the one on the intake pipe to the valve cover. Make sure all the duct is properly seated to the throttle body, and intake air box.

For both Banks to be running rich, I suspect a vac leak after the MAF. Does the engine surge a little at idle?

 

So not really, what usually happens is I come to a stop light, the revs kinda blurp down to 500, and then go back up to 7-800 and just stay there

 

Well I got nothing for now. Since with out live data it's hard to find any direction to go in. I would still try the basics though. Cleaning throttle body it might help the idle drop.
other causes of Running Rich.

Stuck open thermostat
Bad ECT
Like I said without live data to look at. It's pointless to guess.

I did find this article it's some good info to read.
https://www.searchautoparts.com/moto...stics?page=0,0

 

So cleaned the throttle body, as it was quite dirty. Feel a little bit more umph from the car, but the code persists. Thinking of looking at intake manifold, injectors, and changing the spark plugs.

 

Does the car start missing at idle?
Whens the last time you changed the spark plugs?

Before you pull the intake manifold do a basic smoke test to rule out a vacuum leak. I did it with a Swisher Sweet by blowing the smoke in from the brake booster line. Remove the intake tube and wrap the throttle body with whatever you can. So no air can escape. After a few puffs keep blowing into the hose blocking the tube everytime. To prevent the smoke from coming out. Check if you see smoke leaking anywhere besides the throttle body opening. I didn't find any leaks, but my car is asking for Newports now

As for checking the fuel injectors I'd doubt they are bad on both banks.

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So no, I haven't had any misfire problems. One observation though, two actually. When I come to a harsh stop, the car does seem to start shaking a bit, and the rpms get wonky for like 2 seconds, then stabilize. Also drove the same ~140 mi. Back this time with the CEL on, and the car wasn't as efficient on gas mileage with them on as when they we're off.

As for when the last time the spark plugs we're changed? No clue, just recently bought this guy off Craigslist in August. So I'm quite new to the Lexus game 😁

Lol Newports huh.

 

Do you see the the mpg fluctuate on the speedometer? Say it will be steady then jump up or down while driving. On the Avg mode, not Tank Avg.

Well at this point since your running rich enough. Long term driving like that will fry your catalytic converters. If you can take it somewhere to get it properly diagnosed.

 

So it will fluctuate, but it is consistent to whether I'm driving on the hwy (go up) or in the city (fluctuate a bit up and down).

Would you say going to the dealer would be a good idea to get it checked? I have one pretty damn close to me.

 

I'd say go for it since they have Techstream to look at all the data to pinpoint what's going on. If it's a simple fix just pay the diognostic fee, and do it yourself if you can.

On the extreme side if they can't they'll want to throw parts at it until it's fixed. Then that's costly as heck. Unfortunately that's how dealerships work. Wether it's Lexus, or other make dealerships.

 

Hopefully they can find the issue, besides that, I won't let em touch it if they just want to throw parts. Thanks for your help! I'll update once I can figure something out.