Engine warning light error code PO172

[sculpturetim]

Hello, 

Ive been trying to find a solution to my engine warning light and error code P0172, I also have hesitant acceleration from a standing start (for example starting of from the traffic lights)needs to be pressed repeatedly and seems to have a delayed jerky acceleration.

 I have replaced the spark plugs, 02 sensors, the maf sensor, the air filter, the throttle body, i have checked for vacuume leaks. 

 

recently i got an new OBD2 reader which gives live view.  initially i thouight it must be the MAF or an O2 sensor, however ive looked at the graphs for the 02 sensors and they look ok to my untrained eye between 0.1v and 0.9v in a nice up and down wave form, can anybody confirm if my thoughts are correct and if they are looking like they are working, below is screenshots from the obd2 reader for general info and both O2 sensors . For example i can see the long term fuel trim is -45% shown on image 1

Several mechanics have said i should just chuck away the car but i think it has lots of life in it yet, its 20 years old but has been looked after all its life and has only done 53'000 miles. when its not hesitating it drives well

I would like to keep this car on the road

if you have any suggestions i would be most grateful as i am running out of ideas!

[flash22]

as per your previous post it is running ultra-rich and the ECU is pulling fuel like mad

pull the plugs and check the colour do them 1 by 1 so not to mix up the order, post some pics

 

screen one is that ECT after it has been running a while what Is the ECT on a cold engine eg. not started over night?

[sculpturetim]

Thanks for your replies,

Tsikis, in fact the cat is not the original as the original was sawn off by some theives!  i replaced it with an unkown brand, i did find some very small pin hole leaks in the metal casing when i tested it with a shop vac on blow with soapy water for exhaust leaks.( i wasnt sure if it was a problem?), i had some bigger leaks at the slip joints to worry about.  i re pasted slipjoints  and left the pinholes.

I  dont know how to properly test a cat or an ecu? but they both sound plausible problems. 

Im trying to do my best before going to a garage. can most regular mechanics test the cat and the ecu?

Flash, i took a picture of the spark plugs, they were new about a month and a half ago.

previously i showed the Engine coolant temp when it was a warm engine.  i attach a screenshot of the engine coolant temp at start up cold. In fact it took a few moments to get the obd2 reader going so shortly after startup.

 

[flash22]

it sounds like the cat you have is junk there is not much difference between the 2 o2 sensors almost like it has no cat - these cars run rough on anything but Denso plugs (K16R-U11) the black soot shows it is very rich

[sculpturetim]

well, i gave in and took the car to the garage and had 3 experenced mechanics look at it, they said the cat is working fine and there is no air leaks,on the test drive it drove well and passed all the tests on the computor.

before going to the garage i replaced the sketchy eBay 02 sensors for front and rear denso oem 02 sensors and that has helped the hesitation problem which is good , however im still getting the po172 and the engine is still running rich. after the garage visit i replaced the remaining 2 ignition coils for oem ones and reoplaced the mas air flow sensor for denso oem, The car drives quite well now apart from the engine light...

Oner thing i noticed is the mpg readout on the dash is often giving me a reading of 99.9 mpg which sounds an unlikely number for a 20 year old yaris. is this normal?

starting to wonder weather i might have a problem with the ECU? any thoughts.

in 3 weeks im driving the car to Italy and will get a 5 star breakdown  cover just in case. ive tried every thing i can, I'm out of ideas now!