Rach34

Have a 2009 Is250 AWD that had multiple codes. Would lose power if u got on the gas or while going up hills would have to completely shut off the car and turn back on and it would be normal till the next hill or etc. Replaced the MAF sensor and it did help some but still have codes
PO101- Mass Air Flow Circuit Range/ Performace
PO171- Air/Fuel Mixture System Too Lean Bank 1
PO174- Air/ Fuel Mixture Sustem Too Lean Bank 2

Took to a local shop and he checked it out said he couldn’t find any leaks and thinks it’s the fuel pump but isn’t entirely sure. Can someone give me some insight? If it’s the fuel pump he said the back seat would need to be removed and it was under that. Which fuel pump would be best and a good place to buy this? Thanks in advance!!

MikeFig82

iTrader: (13)

Did at any time after you replaced the MAF. Was the ECU reset, or just installed the sensor, and drove?

ECU reset procedure. Its pretty simple if you do the fuse method.

https://www.clublexus.com/how-tos/a/...our-ecu-363500

Once the system is compromised. You need to wipe the memory. Otherwise it's running on the same stored parameters. It will probably take a long time to adjust itself on completed drive cycles.

After ecu rest is done. The car will start on first try then die out this is normal. Just start it back up. Then let it warm up to stabilize the rpms. At first they will be high again this is normal.

It will probably take 15 minutes to stabilize.

Rach34

I wasn’t for sure if it had been cleared so I did the fuse method like u said. I dove my car about 45 minutes later and the check engine light came back on with the traction control light in the first couple minutes.

MikeFig82

iTrader: (13)

Do you have a scan tool? My first option would be check vacuum leaks. Any maintenance done recently in the engine bay?

As for fuel pump related I'd also suspect a clogged strainer filter, and fuel filter before the pump. It's rare they go out on this platform. Eventually they will, but most likely it's being the filters clogged making it work overtime.

This is what a clogged fuel filter looks like.
https://www.clublexus.com/forums/is-...el-filter.html

Rach34

I do but it’s a cheap one I bought off Amazon a Kobra. The car actually ran better when I just drove it just rechecked the codes and it says Fault:02 and Pend:03
PO174
PO101
PO171 P
PO174 P
PO101 P

No work done on the car just regular maintenance oil change and tire rotation. The codes have actually been on my car for quite sometime. The man who looked at it said that he checked for leaks and didn’t see anything. Thanks so much for helping me I’ve been totally lost.

MikeFig82

iTrader: (13)

Did you do the maintenance your self. Changing out air filter etc... etc? Last where did you get the MAF sensor from? It needs to be same quality as OEM.

Did you notice this while just after a maintenance has been performed, or just randomly one day?

The only thing I can see being missed woud be the EVAP purge valve inlet hose. If someone removed the intake hose uncarefully it could dislodge from the hard metal line. You won't notice unless you know what to look for. The leak would be small, but it's a vacuum leak.

When the car is idle does it seem like the engine has a slight shake to it? You'll notice a lumpy idle, and the rpm needle will bounce.

If all checks out the best bet is aquire an advance scan tool. This will show you fuel rail pressure. Though you will have to purchase the package to read the advanced data. All information can be found here:

https://www.clublexus.com/forums/is-...ispreloading=1

Rach34

No I don’t do any of the work myself always the same mechanic who does oil change and tire rotation. It just came out of the blue so not really sure. I got the maf sensor from o’reillys and it wasn’t a oem part. The rpm needle doesn’t bounce.

MikeFig82

iTrader: (13)

If you want to take a gamble on fuel related. I'd probably go with. Having your mechanic just change out the fuel pump filter. Also the strainer pre filter as well. Though that one is a dealer part only. Normally I try to fill up the tank at 1/4 mark. This somewhat prevents sediment from clogging the system being sucked up by the pump module, and once going really low. The siphon hose on the passenger side.

As for the MAF again just suggesting getting a DENSO brand MAF. Advance Auto should have it in stock. The Chinese branded from Autozone, Oriley's are utter junk that probably won't be properly calibrated. It's a critical component for engine management.