First post. '96 Outback 2.5 Auto
Executive summary: Smog test fail, rich idle, No CEL.
Mechanic advises could be Fuel Pressure Regulator, MAF sensor or MP sensor.
Any tips?
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Long Story:
I'm trying to help a little old lady with her Subaru.
Failed smog. Shop changed O2 sensor, gave up. 2nd shop changed Knock sensor, gave up. Two sensors and frustrated mechanics cost $700.
So, I stepped into this mess to help out a friend.
When I got the car the major symptom was a surging idle. I decided to work on that before getting another smog test. Changed air filter, Oil and filter. Cleaned IAC valve by pooring a small amount of Seafoam in it, twice. Changed all small vacuum lines. Cleaned MAF sensor with spray, per the procedure on this forum.
Idle surge is gone. Car runs well, but upon taking it to my friendly (really, he is...) smog check guy he told me it was "full rich" at idle. Suggested it is one of three things.
1. Fuel Pressure Regulator
2. MAF sensor
3. MAP sensor (Vacuum sensor)
Should I test fuel pressure to rule out Fuel Pressure Regulator? Any tips for sorting this out, or experienced guesses?
Below are notes from the shops:
Shop 1:
No notes. changed O2 sensor
Shop 2:
Check Engine light is on also run too rich at idle speed. Scanner Check shows P0505 Idle Control System. Check for Rich Condition, No codes are present. Scanner Data Shows a Oxygen Sensor Bank 1 sensor 1 stay at .000 MV. Customer replace Oxygen sensor and still not working. We installed a computer and still no change at all. Installed back original computer.
Shop 3:
Customer states car will not pass smog check. Engine light is on. Check and advise. See attached paper work. Dignostics based on symptoms actual time used for confirming and diagnosing problem with car. Includes time to road test, hook up test equipment and trace problem to it's cause. Check engine light is on check and advise. **** Scanned computer P0325 Knock Sensor Circuit 1 Bank 1. Checked resistance at Knock Sensor (specs are 400K ohms or more) No resistance @ sensor. Recommend replacing Knock sensor and rechecking. Remove and Replace Knock sensor on vehicle. Old sensor had no resistance and causing MIL light to come on. Cleared code and test drove 10 miles and light stayed off. Rechecking .87V - .86V at idle, readings at 2500 RPM .81V-.83V, sensor is staying rich and not switching properly. Install new sensor. After replacing B1S2 O2 sensor mechanic rechecked readings are still the same .81V - .90V staying rich on the downstream side. Re-installed old sensor back in vehicle. Have checked MAF (Mass Air Flow), TPS (Throttle position sensor) etc... Vehicle does have unsteady idle until unplugged TPS sensor and idle steady's out at about 1500 RPM. TPS 0.60V closed throttle, 4.45V wide open throttle. MAF KOEO 0.00, idle 3-4 GS. Called Dealer and spoke to a mechanic to try to get some insight of what step needs to be taken. Was not able to get any info to help cause. recommend taking vehicle to dealer for further diagnosing.
Thanks for your time. I'll post results.