subura impreza 1.6 2002

Guest · Post by **Guest** » Wed Mar 25, 2009 12:03 pm

i have problem with impreza when you drive car it acts like it is retarding timming or missfiring keep acc pedal to floor it dies splutters then suddenly it takes off when you let go throttle and re accerlete same thing happens keep acc pressed it takes off. this car has no air flow meter on exhaust it has air fuel ratio sensor also has oxygen sensor. oxy sensor shows poor reading on pico scope but no fault on diagnostics but on live data is showwing .22v and not moving iam not sure how to check fuel air ratio sensor i have tried knock sensor. plug leads. coil. fuel pressure. connections map sensor. throttle switch. what i am wondering where does ecu get info when it has no air flow meter. is it from sensors on exhaust would be grateful if some one could point me in right direction

Matt Fanslow · Post by **Matt Fanslow** » Wed Mar 25, 2009 2:47 pm

Does your service information list this engine as having a MAF, a Manifold Absolute Pressure sensor (MAP) or both?

You state that the post cat O2 sensor has a "poor reading". Could you elaborate?

The way I like to test AFR sensors is to use an exhaust gas analyzer (4 or 5 gas) and compare AFR or Lambda readings to what the PCM and AFR sensor reports.

What are your fuel trims doing? Could you give us fuel trim readings at idle, raised rpm (no load 2500 rpm), cruise (under load driving) and while the symptoms are present?

And while we are at, can you provide us with the voltage output of the MAP sensor at idle and at elevated rpms?

Thanks, Matt.