February 26, 20179 yr I have a higher mileage 1998 Legacy Outback (2.5DOHC)that has about 313,500 miles on the clock... it used to be mine, but I have recently gifted it to a friend Valve covers where leaking like a sift... so I changed them It ran smoothly before this, nice crisp throttle response. The new owner purchased Autolite Platinum AP3924... I checked the gap, looked good, I know you should not adjust the gap on platinum plugs.... But I still carefully check them, I have found a bad one once before I typically run NGK BKR5E11 I did not replace the wires as the car was running fine at the time it's a slight stutter off the line, seems fine as the car gets past the blip, it also seems to buck a little bit if you blip the throttle while parked...
February 26, 20179 yr Bad plug wire. Probably on its last legs and disturbing it caused an electron leakage path. They will arc down the side of the plug. Get an NGK set. GD Edited February 27, 20179 yr by GeneralDisorder
February 28, 20179 yr Author I know the rear o2 sensor is broken... rumor has it that platinum plugs do not like it when the fuel mix is not perfect.... can anyone confirm this?
February 28, 20179 yr O2 sensor is not used except for cruise and idle..... narrow band sensor.....can't hurt to replace it if it's bad though. Check the vacuum routing to the manifold/atmospheric pressure sensor and switching solenoid is correct and make sure the switching solenoid works and the sensor is reporting correctly (18 - 24 in/Hg) at idle. Check for signal dropouts in the TPS. A graphing meter helps for this but you can do I with an analog meter too. Digital is useless for testing these. GD Edited February 28, 20179 yr by GeneralDisorder
February 28, 20179 yr Author Waste of money buying autolite plugs for that engine. Get a set of NGK plugs. I totally agree... I told him(Johnny) buy NGK plugs and the worthless parts jokey sold him Autolites... I told him get NGK plugs they just plain work...He thinks the guy at Autozone is a doctor... I explained to him... The doctor is the mechanic who works on your car, he prescribes parts for the repair and makes the repair (I was a mechanic for a well known Porsche repair and performance shop) the pharmacist is the autoparts store's computer... and it aint always right, the pharmacist's assistant is the worthless parts jokey... who likely knows nothing about diagnosis
February 28, 20179 yr Author I see what you are saying but I also doubt that is the issue if it was running fine before changing valve covers.... Also we just replaced the TPS a few months ago.... after that it idled great and ran even better O2 sensor is not used except for cruise and idle..... narrow band sensor.....can't hurt to replace it if it's bad though. Check the vacuum routing to the manifold/atmospheric pressure sensor and switching solenoid is correct and make sure the switching solenoid works and the sensor is reporting correctly (18 - 24 in/Hg) at idle. Check for signal dropouts in the TPS. A graphing meter helps for this but you can do I with an analog meter too. Digital is useless for testing these. GD
February 28, 20179 yr If you just replaced the TPS - where did you get it from? I just had an aftermarket TPS fail about a month after install on an EVO build. Got the dealer part and no issues. New doesn't mean good. It just means it failed once already..... Test, Verify, Replace. Don't troubleshoot with Visa. Doubting isn't knowing. GD Edited February 28, 20179 yr by GeneralDisorder
March 1, 20179 yr Did you replace the little gaskets around the spark plug holes when you did the VCGs? Check the sparkplug tubes for oil. Its not uncommon for oil to leak into there and cause a misfire.
March 1, 20179 yr Throw the Autolites away and get NGK's. They're the only plug that should be in a Subaru. I can't tell you how many times a customer brought me a car after their mechanic did a fresh 'tune up' with Autolites.
March 5, 20179 yr Author Plugs... passenger side rear the ceramic insulator cracked and fell off... new NGKs are running great
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