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slight miss after changing valve covers and plugs


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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...

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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 by GeneralDisorder
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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 

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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

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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 by GeneralDisorder
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