2006 Subaru Forrester Misfire (39,000 miles)

subaru
misfire

#1

My wife encountered a series of hesitations and shudders on return from a round trip from Pittsburgh PA to Elmira NY. The check engine light came on then off. Now, after a local trip at home, the Check Engine light is on and the Cruise light flashes continuously; the cruise control is inoperative and the cancel/ on/off, and other controls have no effect on the flashing “Cruise” indication. Moments of hestitation continue, particularly when slowing & accelerating from stop.

Trouble codes indicate misfire an Cylinders 3&4 with pending misfire codes for Cylinders 1&2. Here is the “freeze Frame” data from an Actron CP9180 scanner:

Non OBD Freeze Frame



Frame 1 Mod $10

TROUB CODE P0303

ABSLT TPS % 78.8

ENG SPEED RPM 1632

CALC LOAD % 100.0

MAF FLOW GR/SE 30.97

MAP KPA 96

COOLANT ?F 147

IAT ?F 78

IGN ADVANCE DE 6.5

ST FTRM1 % 35.1

LT FTRM1 % 3.1

ST FTRM3 % -100.6

LT FTRM3 % -100.6

VEH SPEED MPH 3

FUEL SYS 1 CLSD

FUEL SYS 2 N/A

O2S12 V 0.025

ST FTRM12 % 0.8

OBD2 STAT CA


#2

Short term fuel trims are all out of wack. It looks like, on your engine, that fuel trim is calculated for each cylinder.
Coolant temperature is 147F degrees; which is too low for closed loop operation; yet, the freeze frame shows Fuel System 1 closed loop.
The engine computer sees the MAF (Mass Air Flow) sensor measured the amount of air flow as 30.97 gram per second. You’ll have to go to the tables to see if this is what it should be for the load and speed. The speed is given as 3 mph, at 100% load, with the throttle at 78%. A fairly heavy acceleration was done, and the DTC and freeze frame were set in the engine computer.
Check the engine coolant temperature sensor with an ohm and volt meter.
The VSS (vehicle speed sensor) signal may not be getting where it’s supposed to; so, check that. Check the ohms and volts on the MAF. The values and how-tos are in the repair manual.
This site shows the available repair manuals. Register and check it out: http://www.autozone.com/autozone/catalog/parts/partsShelf.jsp?displayName=Manual+-+Vehicle+Maintenance&currentPage=1&categoryDisplayName=Engine+Management&navValue=15900108&itemId=prod61252&parentId=cat30067