Trouble Code 171 (freeze Frame)

[82DMC12]

Hey Group,

my 94 ES300 has about 104K on it. I have owned it for the last 10K miles. Recently i have noticed that when the car is cold it bucks a little on acceleration until it warms up, then only slightly bucks under certain throttle conditions when warm (very rarely, usually only noticeable when just leaving my driveway cold). I was motivated to really get down and fix it when my check engine light came on while the engine was hot coming off the interstate, giving me a freeze frame code of 171 - engine too lean.

I called up Lexus of Wayzata, MN and found that three O2 sensors, plugs, wires, and a fuel filter will run me about $475. i have not done any of these services during my ownership and are unsure of the car's history.

any probable suspects so i don't drop half a grand and get no results?

With these parts, is it best to stick to OEM parts or will aftermarket do the job just fine? I will spend the money on OEM if they really are superior (like Toyota starters vs. aftermarket).

Thanks,

Andy

[branshew]

I am assuming that the $475 was pricing for the parts only and no labor. I haven't been able to find a single O2 sensor for my 95 for much under $100.

The O2 sensors are relatively easy to replace (like a spark plug) and are fairly accessable. Aftermarket parts would be fine here as long as you get quality ones.

As to the O2 sensors, you could check www.oxygensensors.com to see if they have yours in stock. Get the OEM style from Walker or Denso unless you want to be cutting and splicing the wires on the Universal 4-wire type.

That said, even if all 3 O2 sensors were bad, the bucking and hesitation are probably the result of needing a tune up. I would start with new wires and plugs first. Then try the fuel filter, then go to the O2 sensors if the light comes back on.

[oldrx300]

82DMC12,

I got the same problem with 171 code, so I clean the Mass Air Flow Sensor and the problem went away. I'm 90% sure you have the same problem. Here is the picture I took of Mass Air Flow Sensor (look for oldrx300):

http://us.lexusownersclub.com/forums/index...t=0entry75467

Good luck and hope this will help save you some money,

OldRx300

[82DMC12]

Group,

yes that price quote was parts only (like i would pay someone to do that piddly stuff :-)

after doing some digging this afternoon i found that the accordian between my MAF and throttle body had a rip inside one of the inner folds, almost all the way around!!! this is quite surprising because i keep my engine steam cleaned and detailed, i would think i would have found this a long time ago. I ordered a new accordian (about $90) from Lexus and in the mean time put duct tape around the tear to keep dirt out.

i will pull the plugs tonight anyway and see if they are worth replacing just for preventative maintenence.

Andy

[SKperformance]

With the rip you would have also gotten lots of hot air entering the engine so cleaning the throttle body would be well inorder