I bought my 2005 Subaru Outback around this time last year. It has 123,000 miles and for the most part has been a great car for the last year. This week however I have noticed that it is idling >1k rpm and if I am stopped at a red light the car will occasionally die. When i try to restart it sometimes I need to goose the gas in order to get the engine going again.
I have been trying to avoid the dip in the RPMs by putting it in neutral or park when stopped in traffic, but I have noticed that it will die in park or neutral as well. This happened once before in the summer but never resurfaced but now in winter as the weather got colder it seems to be happening more often. I am going to drop it off at the shop after the new years holiday, but i was curious to see if anyone had similar issues.
Your vehicle has and electronic throttle body. This means there’s no idle air control valve that controls the idle. The electronic throttle body performs this function.
So the first thing to try is cleaning the electronic throttle body.
Are there any diagnostic codes posted in the engine computer’s memory? Does it ever act like it is misfiring? Besides a sticking throttle body, problems with spark plugs, compression, coils, injectors, and engine/exhaust air leaks could cause this.
I swung by Autozone today and they pulled a code for a faulty crankshaft positioning sensor. When I cleaned the throttle body I replaced spark plugs and checked the wires. No issues with the plugs then or now.
That part , if it was failing, could cause this symptom. Its signal is used by the computer to determine when to fire the spark plugs. If it ever just won’t start at all, but cranks ok, check for spark. If no spark during cranking, good chance replacing that sensor will fix that problem. This failure mode however is not common for that part A shop doing an o’scope diagnosis on the crank sensor signal could tell you more.
Maybe with the age of the car there are multiple things going wrong here? Tester’s video did point me towards trying to relearn the idle of an electronic throttle body, seems like there is a system reset for Subarus with this that might help with the low idle.
I’m hoping my mechanic can tell me more about what’s going on with the crankshaft position sensor so i don’t replace the wrong one.
Did that problem start after the battery had been disconnected? If so, the engine computer may just have to re-learn the idle parameters. If so, normal everyday driving should get it working again in a few days. Also this could occur if the battery is weak. When you crank the engine the voltage drop from the weak battery could cause the computer to reset. It will never have time to relearn the idle parameters when that happens, b/c it keeps getting reset every time you crank the engine.