Back story...
Son's car - lives on his own near me
Owned since 91000 miles
Current mileage: 122863
2.5X with auto transmission
Battery replaced a year ago with high quality battery
Timing belt and head gasket replaced ~6000 miles ago
200 miles ago ( 10 weeks) the car started running really poorly and check engine lite came on. I brought my ODBC reader and saw the permanent codes P0303 and P0304. I researched these but also pulled the plugs and found that 3 and 4 were very suety. Local repair shops had a 3 week wait and Subaru dealer never returned my son's 2 calls so I decided to invest in some parts and a little time. I don't usually throw parts at problems without a full understanding but these codes could indicate plugs, wires, coil packs, etc so I:
I took the car out for a test drive and the original horrible running issue was resolved and the engine ran smoothly with plenty of power. However, when I came to a stop, the RPMs would drop to near 0 and sometimes stall or would slowly recover to just above the 1/2 way tick mark between 0 1n 1000 RPM (more on this below). The P0303 and P0404 permanent codes remained but no other trouble codes appeared. (I realize that the permanent codes requires some driving time)
The car sat for 2 weeks due to weather and "life" and during this time I continued to google the issue and kept coming back to the thread above. I went through the relearn sequence again 2 weeks later and now the idle speed dropped significantly coming to a stop but the engine didn't stall, so I thought maybe I just needed to put some miles on it and to clear the P0303 and P0404 codes. I did a 100 mile round trip with a 1 hour stop. The Subi ran wonderfully on the highway (up to 85mph) and on back roads. The idle on brake issue still remained but no absolute stalls - until it was time to return home. Before returning (so after driving 50 miles and sitting for an hour) I checked the codes and the P-303 and P0404 codes were clear and no codes presented - yeah! I then backed up to leave and the engine stalled going into reverse. It stalled twice but I was finally able to back out and get on the road. The drive home was uneventful except for dropping idle speed but no stalls.
So I did some more research and decided to investigate the EGR valve. I tested the resistance on the terminals and electrically it was fine. I took it off and found that it was loaded with carbon deposits. It was the original EGR. For grins I started scraping out the carbon and easy removed 2 heaped tablespoons of very fine dust and some chunks. Rather than continue cleaning I decided it was cheap money to replace the EGR and gasket - which I did yesterday. I left the battery disconnected from the nite before. After installing the EGR I did the relearn sequence again and went for a drive.
I certainly felt like the engine had more pep and I was encouraged. The idle speed did continue to drop but not as low as before so no stalls. And then I noticed something when I pulled into my driveway. As I braked to a stop, the idle dropped to just above that 1/2 line between 0 and 1000 RPM and as I put the car in to Park, the idle speed immediately came up to right below the 1000RPM line and idled nicely. Curious, so I test this several times - putting the car in drive and reverse and then park while sitting in the driveway and this was 100% repeatable. I have a short video of this but can't post it here but here's a link to my hosting site: New Miscellaneous-photos
So, I suspect this is the root of the idle speed drop and stall issue. I've searched but can't find any definitive solutions or diagnostics - hence I'm posting this! Any help, recommendations, and insights greatly appreciated.
Son's car - lives on his own near me
Owned since 91000 miles
Current mileage: 122863
2.5X with auto transmission
Battery replaced a year ago with high quality battery
Timing belt and head gasket replaced ~6000 miles ago
200 miles ago ( 10 weeks) the car started running really poorly and check engine lite came on. I brought my ODBC reader and saw the permanent codes P0303 and P0304. I researched these but also pulled the plugs and found that 3 and 4 were very suety. Local repair shops had a 3 week wait and Subaru dealer never returned my son's 2 calls so I decided to invest in some parts and a little time. I don't usually throw parts at problems without a full understanding but these codes could indicate plugs, wires, coil packs, etc so I:
- disconnected battery
- replaced plugs with properly gapped NKG BKR5EGP plugs
- replaced plug wires with quality wires
- replaced ignition coil pack
- removed and carefully cleaned the MAF sensor as per instructions here
- oil and filter change
I took the car out for a test drive and the original horrible running issue was resolved and the engine ran smoothly with plenty of power. However, when I came to a stop, the RPMs would drop to near 0 and sometimes stall or would slowly recover to just above the 1/2 way tick mark between 0 1n 1000 RPM (more on this below). The P0303 and P0404 permanent codes remained but no other trouble codes appeared. (I realize that the permanent codes requires some driving time)
The car sat for 2 weeks due to weather and "life" and during this time I continued to google the issue and kept coming back to the thread above. I went through the relearn sequence again 2 weeks later and now the idle speed dropped significantly coming to a stop but the engine didn't stall, so I thought maybe I just needed to put some miles on it and to clear the P0303 and P0404 codes. I did a 100 mile round trip with a 1 hour stop. The Subi ran wonderfully on the highway (up to 85mph) and on back roads. The idle on brake issue still remained but no absolute stalls - until it was time to return home. Before returning (so after driving 50 miles and sitting for an hour) I checked the codes and the P-303 and P0404 codes were clear and no codes presented - yeah! I then backed up to leave and the engine stalled going into reverse. It stalled twice but I was finally able to back out and get on the road. The drive home was uneventful except for dropping idle speed but no stalls.
So I did some more research and decided to investigate the EGR valve. I tested the resistance on the terminals and electrically it was fine. I took it off and found that it was loaded with carbon deposits. It was the original EGR. For grins I started scraping out the carbon and easy removed 2 heaped tablespoons of very fine dust and some chunks. Rather than continue cleaning I decided it was cheap money to replace the EGR and gasket - which I did yesterday. I left the battery disconnected from the nite before. After installing the EGR I did the relearn sequence again and went for a drive.
I certainly felt like the engine had more pep and I was encouraged. The idle speed did continue to drop but not as low as before so no stalls. And then I noticed something when I pulled into my driveway. As I braked to a stop, the idle dropped to just above that 1/2 line between 0 and 1000 RPM and as I put the car in to Park, the idle speed immediately came up to right below the 1000RPM line and idled nicely. Curious, so I test this several times - putting the car in drive and reverse and then park while sitting in the driveway and this was 100% repeatable. I have a short video of this but can't post it here but here's a link to my hosting site: New Miscellaneous-photos
So, I suspect this is the root of the idle speed drop and stall issue. I've searched but can't find any definitive solutions or diagnostics - hence I'm posting this! Any help, recommendations, and insights greatly appreciated.