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Auto Psychic
Auto Psychic, ASE Certified Technician
Category: Car
Satisfied Customers: 1437
Experience:  semi retired mercedes benz master guild technician
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I have a 2005 Kia Rio with 170,000 miles on it that I bought for my wife to drive to school. However, the car has problems and I knew it when I bought it. So, these are the codes.

P0170 - Fuel trim bank 1 - too rich too lean
P0507 - IAC system - RPM higher than expected
P0301,P0302,P0303,P0304,P0300 - Misc. misfire and misfire in all cylinders.

-I have cleaned the IAC and it was opening and closing ok.
-I cleaned the throttle body.
-I have re-gapped the plugs to .030 from .040-.045.
-I do have spark in all cylinders.
-Compression test showed that all cylinders are within 10% of 135psi.
-Performed a back pressure test which showed <1psi @ idle and at a somewhat steady 2500rpm, however when revving I can the back pressure up to about 6psi but then it comes right back down.
However, I took off the short section of exhaust pipe that has the downstream O2 sensor on it and discovered that the catalytic convertor is cleaned out completely. I had done this before to a mustang and it ran OK with the exception of the bad sounding exhaust, but could the lack of the catalytic material cause these symptoms?
- I have found documentation of the timing belt being replaced about 30,000 miles ago.
I checked to make sure that the two cam marks ar lined up and they are, but I cant see the crank mark.

The car will start up fine, in the garage it runs a little rough like misses. It will rev fine but it wont hold a steady RPM, it drops out.
When driving the car it will cut out for the first couple of miles and then if I come to a stop it will take forever to get back up to speed. It boggs down and will eventually stall. If I am on even a slight hill, it will not make it. I have had to back down the hill and do a K turn into a side street and find another way home.
It feels like my 88 mustang that had a bad Ignition Control Module and my 91 Camaro that had a bad injector.
I have no idea what else to do without throwing parts at it. I bought a new IACV and TPS but I don't want to put them in because the two of them were $200.00 and I am not convinced that they need to be replaced.

I have already talked with one mechanic and he gave me the diagnostic charts for the P300 and P500 codes and advised me to check for vacuum leaks. However, I need to get my hands on a scan tool to perform the tests on the charts.

Country: United States
Make (manufacturer): Kia
Model: Rio
Year: 2005
Engine (optional): 1.6

Auto Psychic :

hi, i'll be happy to help in any way i can.

sorry to hear of your misfortune :(

thats a lot of miles for an 8 year old kia.

they didnt build them as well as they do now.

having said that, the most common cause of all that you describe is a bad mass air flow sensor.

the gutted cat i should think would also be of concern, re: your next smog test.

also the back pressure, pieces of the previously plugged cat clogging the exhaust system??

does that help?


Yes that is a lot of miles.

I went to a yard and pulled a mass airflow sensor off of an 03. Will that one match up with mine, it looks identical but the numbers are not the same.

The back pressure, the results that I got are they indicating excessive backpressure or is it normal for the backpressure to climb when revving and then drop. At steady idle it stays at or about 1psi.



Also, is there anyway that I can test my MAFS on the car?


I have tried to reply, but I have not gotten a response



no reply

Auto Psychic :

poor service, ouch, because i'm not around on a holiday.

anyway, the maf sensor should be ok.

stills sounds like a lot of back pressure, i think i'd like to run it with the exhaust unorked and the maf sensor, just to see where were at.


Auto Psychic and 4 other Car Specialists are ready to help you
thank you for trusting the auto [email protected]/pearl, always happy to help, gary
Customer: replied 5 years ago.

No thanks

any luck?
Customer: replied 5 years ago.
I ordered a catalytic converter. Should be here by the end of this week.