I'm getting P0171 and P0174 and restricted performance. It happens only on start up and last for about a mile or two. I know this means lean on both banks. My understanding is that the fuel injection is on open loop until the engine warms up. I this means that any output from the 02 sensors does not mater when on open loop. Any ideas?

 

There's a couple of things to check...

 

With your OBD reader in data mode, read the air temperature: this sounds like the temp sensor has failed and the ECU thinks the car is still warm and is not enriching the incoming mixture for cold start.

 

Ran test this morning early (so sun did not heat up black car) on cold engine. Air temp 71degrees F, reading 82. As soon as cranked immediately rose to 88. When engine warm and driving 45 mph reading 15 degrees higher than ambient.
When cruising after warm, restricted performance came on a couple times for maybe 15 seconds.
Ran a smoke test and no vacuum leaks.

 

For those across the pond:
(F − 32) × 5/9 = C

 

that’s what air fuel sensors are for my guy

closed loop instantly

 

Had my original MAF sensor. Replaced before I figured out my prior lean burning was from an air leak. Put that one on. This one reads ambient air about 5 F under true temperature.

 

air fuel sensors

upstream of the cats

 

Not sure what you’re trying to convey. Bad 02s? Seems doubtful both would fail at the exact same time.

 

i’m telling you the car is in closed loop near instantly

 

It was the MAF. Replaced with a new one and problem gone. Bad one only two years old. Brand Wagner.

 

I guess they don't make 'em like they used to.

 

This is why I ask people if it’s the original MAF or an aftermarket one. Probably 90% of the time if it’s the original one, it just needs a good cleaning. We’ve had customers 171/174 codes in their car and I can tell they just replaced them with an A/M pos one. I have the boss get on the horn with the customer and see if they have the prior one and about 99% of the time they got tossed. 🤦🏼‍♂️ We call our sources and locate a used one vs another A/M MAF.

 

Tried MAF cleaner on Wagner first. No change. I had the one in the car when I bought it. Not sure if original equipment. Cleaned with MAF. Drove to work fine. On way home it completely failed. Had to keep modulating throttle to make it home.

 

Albeit it’s been a long time but, if you disconnect the MAF sensor, I think you’ll have a little bit better drivability vs fighting a dead sensor with the throttle. It has a failsafe mode in the ECM to run the engine if it was disconnected. It would say “Denso” and a Jaguar part number on top of the maf if it was original.