My Jag xk8 is hesitating during acceleration and returning the system lean code which if i remember right is 171 and 174. I have read through all the blogs here and checked all the breather tubes and cleaned the TB and mass air flow.
I have 110 thousand trouble free miles on the car. Seems to do fine when it is cold and it is getting worse more now everyday

I have read through Alldata and the autozone computers systems and they all say it is the down stream o2 sensors, so i naturally check my car but find I only have 2 o2 sensors and not 4. The autozone computer return no parts for a C model motor and there is a C in my vin code. Any help would be appreciated

 

There are four. Two above the cats and two after. 174 code is for the O2 sensors. I think the 174 is for the driver side. You'll probably end up changing both.

 

Thats the problem, there are only 2 the two above the cats, none below the cats, I can see where there suppose to be, the bungs have not been drilled or tapped so i assume it is stock.

 

What is the year and last 5 digits of your VIN?

The P code tables changed somewhat during the years. On the '97 the chart does not list a downstream O2 sensor but the engine emission control description does. Let's make sure we start with the right chart.

 

I purchased my 99 XK8 sight unseen out of state, with the same codes. Got a great deal because of it, and it turned out to be the snorkel tube from the air cleaner to the throttle body was brittle and cracked on the undersideof the "accordian" portion. Did a careful taping job and fine for 11 months now.

 

In case anyone is still fallowing this thread if figured my problem out.
Turns out to be the mass air flow sensor, although i cleaned it in the tube a half dozen times, this time i took it out of the tube and cleaned in all the hidden holes especially the heater wire section that could not be cleaned from it sitting in the tube. worked perfect ever since.

 

Hey, good news! Thanks for the follow up, much appreciated.

 

I wish my ongoing problem with P171, and P174 codes was as easy to find. My Jag is at the second Shop now, since the first mechanic gave up on finding the root problem. These guys have now had it since last week, and they too are stumped so far! They have given it two Smoke Tests to date, so unfortunately for me, it is not just a Vacuum Leak.
Not fun!
Brian

 

Wanna try a new air pipe (the big black bellowed one?) I've got a new one you can 'borrow'.

 

Thanks for the offer Matt. I would if I though that it would help, but this one has been "Smoked" more than a Crackhead's favorite Glass Pipe, and it still come up as perfectly airtight! The search continues.............
Brian

 

brian, if the plastic air tubes are all good, then the other known issue for these codes on THIS car and the XJ is the mass air flow sensor.. you can try and clean keeping your fingers crossed, but I replece them since people here useally dont like to have to keep coming back for the same issues

 

Brian, did you start your own thread with your Pcodes and a detailed summary of your diagnostic approaches? I couldn't find one if you did. i don't want to muddy up pilotcraig's thread with other suggestions/questions if your cause leads us down a different path.

 

Hi Matt,
OK, will do.

Brutal,
Thanks, I'll respond in the new thread.
Brian

 

like i said i cleaned my mas air flow sensor about 6 times. but i didn not get into one hole that has the other two wires i think they are the heater wires. I also cleaned up the throtal body with a lintless rag and carb cleaner. again then it ran fine. so im thinking mainly it was those heater wires that were dirty. check with your mechanic and see if he took the maf out of the tube to clean it.